Insomnia Causes and Treatment

Natural Insomnia Program

The Insomnia Exercise Program is a simple audio program that works to Train Your Brain to switch from normal, fast-paced brain waves to slow, delta and theta waves and put you to sleep mind and body naturally. This is a 2-part program. Part 1 is a 25 minute audio where I lead you step by step to reach those slow theta and delta stages that knock you out in a deepest sleep of your life. This is done through a combination of mind, eye and relaxation exercises. Part 2 is a 50 minute audio of sound therapy where you hear the relaxing sound that draws you into the wonderful land of dreaming. After youve listened to the audio a few times, youll most likely be sound asleep long before it even comes to this part but it is important because it will draw you into deeper and deeper sleep so you dont wake up after a few minutes and not be able to doze off again. All you have to do is listen to the audio in your bed and get ready to fall asleep! More here...

Natural Insomnia Program Summary

Rating:

4.7 stars out of 15 votes

Official Website: blueheronhealthnews.com
Price: $49.00

Access Now

My Natural Insomnia Program Review

Highly Recommended

Maintaining your trust is number one. Therefore I try to provide as much reliable information as possible.

I highly recommend you to consider Natural Insomnia Program as your first choice.

The Pineal Gland A Melatonin Factory On A 24hour Schedule

At the time I started working in this field around 1968, Aaron Lerner's discoveries of melatonin and the high concentrations of melatonin in the pineal gland were well known (17,18), as was the high amount of serotonin in the pineal gland (19). Julie Axelrod and his coworkers were generally interested in biogenic amine metabolizing enzymes, so it was not long before Lerner's findings led to their demonstration that the pineal gland had the enzymatic machinery required to convert serotonin to N-acetylserotonin and N-acetylserotonin to melatonin (20,21). This established the pineal gland as a melatonin factory. The concept that there are 24-hour rhythmic changes in pineal indoles came from studies by Quay (22,23). He had developed fluorescent techniques to measure pineal melatonin and reported that there was a large day night rhythm in serotonin and melatonin. The large circadian changes in these compounds were intriguing and immediately raised questions in the minds of curious...

Isolation of Two Putative cDNA Melatonin Receptor Fragments

Polymerase chain reaction (PCR) amplification was accomplished using degenerate primers based on the peptide sequences INRYCYIC and MAYFNSC, which are located near the 3rd and in the 7th transmembrane domains, respectively, and are conserved among the Xenopus and the mammalian (MeU and MeU) melatonin receptors (27-29).Genomic DNA was subjected to 30 cycles of PCR amplification (94 C, 45sec 45 C, 2min 72 C, 2min) using 200nM of each degenerate primer, and 1.25U of TaqDNA polymerase (Appligene). PCR products were run on 1.5 agarose gel. The amplified DNA was purified and cloned into pGEM-T vector (Promega). The nucleotide sequences of recombinant clones were determined using ABIPRISMTM Dye Terminator Cycle Sequencing Ready Reaction Kit (Perkin Elmer) with Ampli-Taq DNA Polymerase, FS. Primers were synthetic oligonucleotides that were either vector specific or derived from sequence information. After sequence determination, specific primers (Figure 1) were designed to amplify a fragment...

Comparative Aspects Of Signal Transduction Cascades Regulating Melatonin Biosynthesis

As outlined above the transcriptional regulation of the AANAT plays an important role in up- and downregulation of melatonin synthesis in the rodent pineal organ. This scenario, however, does not apply for all vertebrates, not even for all mammals. In the sheep, posttranscriptional mechanisms are more relevant for control the rhythmic melatonin biosynthesis, as the mRNA for AANAT fluctuates only marginally (18). Accordingly, plasma melatonin concentrations rise after the onset of darkness much faster in sheep than in rodents (2). Chicken, trout and most other non-mammalian vertebrate species possess photo-receptive pineal organs. Thus light rather than adrenergic-stimuli appear as primary regulators of the melatonin synthesis in these species. In the chicken pineal organ AANAT mRNA fluctuates, but with a much smaller amplitude than in the rat (36). Thus, chicken AANAT seems to be regulated at both, the transcriptional and the post-transcriptional levels. Accordingly, ICER has been...

Melatonin As A Seasonal Time

Melatonin transduces the effect of changes in daylength in photoperiodic mammals and thus times seasonal cycles in reproduction, moulting, somatic growth, fattening and other seasonal characteristics. This is the best characterised biological role(s) of melatonin (1,60,61). The photoperiodic transduction mechanism involves light perception by the retina, entrainment of the circadian rhythm generating system in the SCN and the inhibitory effect of light on the secretion of melatonin by the pineal gland (see other chapters). The result is that melatonin is secreted only at night, and the duration of secretion varies with the annual cycle in nightlength and thus daylength. The duration of melatonin secretion appears to be the critical parameter affecting the melatonin target tissues since daily infusions of melatonin of appropriate duration and maintained for many weeks, mimics the effect of long day (short period infusion) and short days (long period infusion) on seasonal physiology...

The Pars Tuberalis As A Target Site For Melatonin

Until a decade ago the pars tuberalis (PT) had been dismissed as an accessory endocrine gland to the pars distalis (PD) (18). A major re-appraisal of this view was demanded when melatonin receptors were localised to this gland in rodents and sheep, yet these receptors were apparently absent from the pars distalis, at least in the post-neonate (17). This suggested that the pars tuberalis has a function related to photoperiod and melatonin, and one distinct from the pars distalis. Considerable focus and interest in the pars tuberalis was generated also because of all the central target sites for melatonin identified through radioligand binding in mammals, it was the only site labelled by 2-125I-iodomelatonin in each of the species examined (17), suggesting a common function. In some species such as the ferret, it is the only central site of action that has been identified (24). These data, together with its anatomical position, provided strong support for a major role of the PT in the...

Intracellular Mechanisms Of Melatonin Action

Melatonin receptors are coupled to the intracellular effectors via GTP-binding proteins. In the presence of GTP or non-hydrolysable GTP derivatives affinity of the melatonin receptors for 125I-melatonin is decreased (15). The effects of melatonin in the pituitary, including inhibition of LH release and the effects on 2nd messengers are abolished after preincubation with pertussis toxin (PTX 27). This indicates that the receptors are coupled to G-protein(s) belonging to the Gi family. Also the effects of melatonin in SCN are mediated by Gi preincubation with PTX blocks the effect of melatonin on spontaneous electric activity (8). Gi family consists of 5 subspecies 3 Gi and 2 G0 proteins (2,17). It is not clear which of these G proteins is involved in transduction of the melatonin signal.

Melatonin And Prenatal Communication Of Circadian Phase

Reppert and Schwartz (52) removed various endocrine organs in an attempt to identify a hormonal signal necessary for entrainment of the rat fetus. Removal of the pituitary, ovaries, adrenals, thyroid parathyroid or pineal (each surgical procedure performed in separate groups of animals) did not disrupt prenatal synchronization (although results with pinealectomy were somewhat unclear). An alternative strategy is to identify stimuli which can entrain the fetal circadian clock when given periodically during gestation to SCN-lesioned dams. Three treatments which can entrain the fetal clock have been identified in this way restricted feeding, timed administration of D1-dopamine receptor agonist, and timed administration of melatonin. Timed administration of melatonin is the third signal capable of entraining the fetal circadian clock. Melatonin plays an important role in circadian organization of several non-mammalian vertebrates, and exogenous melatonin can influence circadian...

Signal Transduction by the Mel 1a Melatonin Receptor

The hormone melatonin plays an important role in a variety of physiological responses including circadian rhythm regulation, seasonal reproduction in mammals, sleep and vision (21). It is thought to mediate its effects through high affinity GPCRs. The Mel 1a melatonin receptor subtype (now also referred to as the mti receptor) is located in the suprachiasmatic nuclei (SCN) of the hypothalamus and the pars tuber-alis of the pituitary and is believed to mediate melatonin's actions at these sites (22). However, the biochemical mechanisms underlying the effects of melatonin are not yet fully understood. The multiplicity of pharmacological effects associated with Mel la receptor activation suggests that receptors may couple to more than one G protein. Activated Mel 1a receptors have been shown to inhibit cAMP accumulation through activation of pertussis toxin-sensitive G (G 0) proteins (23). Recombinant Mel 1a receptors were also shown to activate Kir3.1 3.2 potassium ion channels, to...

The Role Of Melatonin

For all seasonal rhythms (reproduction, hibernation, daily torpor, moulting, changes in pelage quality and or colour, body weight regulation, etc . . .) and for all mammalian species studied to date, photoperiodic information is integrated through variation in the duration of the nocturnal peak of Mel, which parallels the length of the night. High affinity melatonin binding sites receptors have been identified within several brain regions (for review see 41,49,68) including, in most species, the SCN (79). Daily exogenous melatonin administration is known, probably through an action on the SCN, to entrain free-running locomotor activity rhythms of the rat (2,3), Djungarian and Syrian hamster (35) to a 24h period and to accelerate reentrainment of the locomotor activity rhythm after a shift of the L D cycle. This action of the SCN has been confirmed by some in vitro studies. Neurophysiological recordings from SCN slices have identified neuronal firing rate rhythms which are responsive...

And of the Pineal NAT Rhythm by Melatonin

A single evening melatonin administration phase-advanced instantaneously the evening rise in the light-induced SCN c-Fos immunoreactivity (31). Similarly, a single melatonin administration before the evening dark onset phase-advanced instantaneously the evening pineal NAT rise (6). The magnitude of phase shifts of the intrinsic SCN rhythmicity induced by melatonin administration in vivo was similar to the magnitude of phase-shifts of the pineal NAT rhythm and was less than half of the magnitude attained in vitro experiments following melatonin application to the rat SCN slices during late subjective day (6,26,31). Importantly, melatonin administration in the late day phase-advanced just the evening NAT rise, but not the morning decline (6). Recently, it has been reported that daily melatonin administration at the time of the former dark onset keeps the rhythm in the pineal melatonin production entrained to the 24-h day just for a few weeks after a release of rats from a LD cycle to...

Disorders of sleep Sleep complaints

The starting point for the clinician is the patient's sleep complaint. They are of three basic types not enough sleep or unrefreshing sleep (insomnia) The detailed accounts later in this section are organized in relation to these main types of sleep complaint insomnias ( Chapiei.4.14., 2), excessive daytime sleepiness (Chapter.4.14.3), and parasomnias (Chapter 4.14.4). In recognition of the frequency with which sleep disturbance complicates physical and mental illness, additional accounts are then provided of sleep disturbance associated with psychiatric conditions ( ChapteL4.14.5) and with medical disorders (ChapteL4.14. ). Sleep problems in childhood and adolescence are discussed in Chap.teL,9 2 ,9, with a separate account regarding preschool children in C.h p.t.eL9. 2 .8 The relationship between mental retardation and sleep disturbance are considered above, and common sleep problems in the elderly (which are common and troublesome (36> ) are discussed in Chapter 8.6. Whatever the...

International Classification of Sleep Disorders Revised

Elaborate classification schemes developed by enthusiastic experts can be daunting to the non-specialist. However, despite its apparent complexity, there is much in favour of using the International Classification of Sleep Disorder system (developed from wide international consultation) especially to standardize diagnosis in clinical work and research. The revised International Classification of Sleep Disorders (ICSD-R)(3.Z> is the latest in a number of attempts to organize rationally the various ways in which sleep can be disturbed. The 80 or more different sleep disorders, occurring in adults and children, are grouped as shown in Tabje 1.

Treatment approaches for sleep disorders

In clinical practice the pharmacological approach to treatment is generally overemphasized, especially the use of hypnotic-sedative drugs. Tabled. provides some indication of the wide range of available types of treatment, as well as general principles of management, for adults and children. They are arranged roughly in order of the frequency of their use in the comprehensive management of sleep disorders in general. An appropriate choice from this range requires an accurate diagnosis of the underlying sleep disorder. Further details are provided in later contributions to this section. Claims for the effectiveness of these various measures are based on widespread clinical experience and reports. Few randomized controlled clinical trials have been published as yet. Table 2 Examples of treatment approaches for sleep disorders

Sleep education and sleep hygiene

The simple provision of information ameliorates the sense of being out of control. Inaccurate attributions are challenged and misunderstandings corrected by understanding what sleep is, how common insomnia can be, how sleep changes with age, good sleep hygiene practices, and some facts about sleep loss. Similarly, sleep hygiene provides patients with a starting point for self-management. These techniques are best construed as introductory and will not of themselves treat insomnia effectively.

REM sleep behaviour disorder

Although various aspects of REM sleep behaviour disorder have been identified by European, Japanese, and American investigators since 1966, (34) REM sleep behaviour disorder was not formally recognized and named until 1985, (35> and it was incorporated within the international classification of sleep disorders in 1990. (1 A typical clinical presentation of REM sleep behaviour disorder is contained in the description of the index case. A 67-year-old dextral man was referred because of violent behaviour during sleep 4 years before referral he experienced the first 'physically moving dream' several hours after sleep onset he found himself out of bed attempting to carry out a dream. This episode signaled the onset of an increasingly frequent and progressively severe sleep disorder he would punch and kick his wife, fall out of bed, stagger about the room, crash into objects, and injure himself his wife began to sleep in another room 2 years before referral. They remain happily married,...

Lifespan and the Circadian Insomnias

One obvious feature of the circadian insomnias apparently not commented on previously is their relationship to age. In Figure 2 the insomnias are arranged not in the order presented in the diagnostics manual (63) but according to time of life. It becomes clear that there is a progressive change with age that parallels changes tothe circadian pacemaker evident from animal studies though not necessarily yet demonstrated in humans. A review of sleep disturbances, changes to circadian rhythmicity and the chronobiotic potential of MLT in retarding aging has been given elsewhere (12,42). Briefly, a large body of evidence, mainly animal but some human, indicates that with age circadian period is altered, amplitude is reduced, alpha-rho loses its definition, stability to environmental challenge is reduced (e.g. phase shifts of the zeitgeber), internal desynchrony (humans) and splitting (rodents) increases. In addition, a number of changes to the circadian organization of the sleep-wake cycle...

Presence ofMelatonin Receptors

High affinity 2- 125I -iodomelatonin binding has been demonstrated in cerebral arteries of rat (46,53,54), non-human primates (48), and humans (48). Initially, binding was found in arteries associated with the circle of Willis, e.g. anterior and middle cerebral arteries (53). Subsequently, 2- 125I -iodomelatonin binding was observed in inferior cerebellar, vertebral, spinal, and internal carotid arteries as well (48), suggesting a widespread distribution of melatonin receptors in the cerebral circulation. Interestingly, the density of 2- 125I -iodomelatonin binding sites in rat cerebral arteries is modified during the female estrous cycle (46), postnatal development (38) and in genetic hypertension (54). Saturation analysis of binding to rat anterior cerebral arteries indicated two affinity states for 2- 125I -iodomelatonin (Kd of 13 pM and 823 pM) and a sensitivity to guanine nucleotides (9). In slices of rat cerebral arteries, melatonin inhibited forskolin-stimulated cyclic AMP...

Melatonin Duringaging

The pineal gland, through its hormone melatonin is involved in animal and human reproduction. It has been suggested that melatonin may be involved in the aging process (8). Melatonin is produced and secreted into the blood in a circadian rhythm with maximal production always during the dark phase of the day. The 24h rhythm of melatonin production is very robust in young animals, but this circa-dian rhythm deteriorates with age. Thus, in old animals the amounts of melatonin secreted are lower than that of young individuals and the supplemental administration of melatonin may be beneficial in delaying age-related degenerative conditions (7). Long-term melatonin treatment in rats can postpone the age related decrease in survival rates, circulating sex steroids and 125I-melatonin binding sites in the brain (5).

Clinical Features Insomnia Symptoms

Although diagnostic and polysomnographic signs of patients with UARS differ from patients with OSA, the clinical features between these two sleep disorders overlap. Differential clinical features are given in Table 2. Recently, it has been suggested that patients with UARS may present a link to functional somatic syndromes (52) and therefore differ from patients with OSA. However, this study included only 75 patients with 25 patients in each group (UARS with AHI < 10 hour, mild-to-moderate OSA and severe OSA). Among those functional somatic disorders, UARS patients presented significantly more often with headaches, irritable bowel syndrome, sleep-onset insomnia, and alpha-delta sleep. Also, the proportion of women in the UARS group was significantly higher than in the other two groups (52). With respect to insomnia, data from Guilleminault et al. (53) show that sleep-onset insomnia as well as sleep maintenance insomnia are frequent complaints. The occurrence of insomniac problems...

The Antiproliferative Effects Of Melatonin On Experimental Pituitary And Colonic Tumors

It has been repeatedly shown that the pineal hormone melatonin (MLT) inhibits the growth of various experimental tumors in rodents. The oncostatic action of MLT is connected, at least in part, with its antiproliferative effects on the tumor cells. However, the molecular mechanisms by which MLT suppresses cell proliferation still remains unclear. It was suggested that MLT acts not only via membrane receptors but also via nuclear binding sites and the latter are identical with so-called RZR ROR a-receptors (2,6). Since a synthetic thiazolidinedione compound CGP 52608 has been recently shown to be an exogenous ligand for RZR ROR receptors it seemed to us worthwhile to see whether it exerts also the antiproliferative effects. We have studied the effects of MLT and CGP 52608 on cell proliferation of the diethylstilbestrol (DES)-induced rat pituitary tumors and of the murine colonic adenocarcinoma Colon 38.

Sleep Apnea And Insomnia Definition and Prevalence of Insomnia

Insomnia is defined as a repeated difficulty with initiating sleep, maintaining sleep, a final awakening that occurs much earlier than desired, sleep that is nonrestorative or of generally poor quality that occurs despite adequate time and opportunity for sleep and results in some form of daytime impairment (e.g., fatigue, daytime sleepiness, mood disturbance, cognitive difficulties, and social or occupational impairment) (30,31). It is well recognized that most of us have experienced insomnia at some time during our lives (31). In most cases, however, it is a transient problem in response to stress, illness or sudden change in life situations and resolves quickly when precipitating factors abate. Chronic insomnia that persists over time and contributes to various types of dysfunction remains a greater concern. Results of epidemiologic studies generally suggest that chronic or persistent forms of insomnia are relatively common but the prevalence estimates obtained in these studies...

Effect of Insomnia on Sleep Apnea Treatment Outcomes

In addition to the role of insomnia in prevalence and diagnosis of sleep apnea, it must also be appreciated that it can have profound effect on treatment outcomes as well. For those practicing clinical sleep medicine, it is not difficult to understand that associated complaints of insomnia or depression, which are common in patients with SDB may contribute significantly not only to initial difficulty with acceptance and adjustment to CPAP therapy, but also contribute to suboptimal adherence for continued long-term use. This has been addressed to some extent by Engleman and Wild (44). Krakow et al. (45) demonstrated clinical cures or near-cures with combined cognitive behavioral therapy and CPAP treatment for SDB in 15 out of 17 subjects with SDB and chronic insomnia. It must also be noted that sedatives and hypnotics used for insomnia may have adverse effects on sleep apnea (46).

The Function Of Melatonin In Chenopodium rubrum

The data mentioned above indicate that the melatonin rhythm in C. rubrum is similar to the rhythms described in vertebrates. Therefore, we investigated possible effects of melatonin application on photoperiodic flower induction of C. rubrum. 4.5-day-old plants were induced to flowering by a single 12-h darkness and the chemicals, dissolved in DMSO and diluted with water, were applied onto the cotyledons and apical parts at different times. The percentage of flowering plants was assessed after 7 days of futher growth in constant light. Melatonin, several putative precursors, melatonin agonists and antagonists and inhibitors of tryptophan decarboxylase were tested. Of these compounds, only melatonin and the agonist CGP 52608 showed significant effects. CGP 52608 (a thiazoli-dine dione) was shown to bind specifically to putative human nuclear melatonin receptors RZRa (13). CGP 52608 in concentrations from 2 x 10-5M to 3 x 10-4M reduced flowering when applied 3 or 1 h before, or 2 h after...

REM sleep behavior disorder

REM behavior disorder (RBD) (Schenck et al., 1986, 1987) is a sleep disorder characterized by the occurrence of muscle activity during REM sleep with the occurrence of dream enactment (Schenck et al., 2002). REM sleep without atonia (RWA) shows abnormal muscle activation during REM sleep without manifest behaviors. Polysom-nographic findings of RBD include excessive RBD or RWA is present in 25-50 of PD patients (Comella et al., 1998 Boeve et al., 2001 Gagnon et al., 2002). PET scans have shown reduced striatal dopamine innervation and loss of brain vesicular monoamine transporter (Albin et al., 2000 Gilman et al., 2003). Animal experiments implicate specific brainstem nuclei as the anatomic basis for RBD (Lai and Siegel, 2003). Cross sectional and longitudinal evidence suggests that idio-pathic RBD may in fact be a harbinger of PD or other synucleinopathy (Schenck et al., 1996 Boeve et al., 2003 Eisensehr et al., 2003) and that the association of PD and RBD indicates more extensive...

Pattern and significance of sleep disorders and behaviours in children compared with adults

Some sleep behaviours which are developmentally usual in children are abnormal in adults and require investigation. Examples are nocturnal enuresis and repeated napping. Certain sleep disorders are seen exclusively in children (e.g. sleeplessness caused by infantile colic). Others, such as settling problems and confusional arousals, occur primarily in children (see later). Some sleep disorders thought to be confined to adulthood are now recognized in children. While much attention has been paid to OSA in adults, it is now thought that at least 1 per cent of children have this condition to some degree. Narcolepsy starts by the age of 15 years in at least one-third of cases. Even REM sleep behaviour disorder (once thought to be confined to elderly males), or something similar, has been reported in children and adolescents. ( i>

Manifestations of sleep disorders

The clinical features of basically the same sleep disorder can be very different in children compared with adults. The overall behavioural effects of excessive sleepiness in adults is a reduction of physical and mental activity. In contrast, its effect in young children can be increased activity with irritability, tantrums, or other behavioural difficulties. Some types of attention-deficit hyperactivity disorder ( ADHD) are thought to be the result of sleep disorders (OSA, periodic limb movements in sleep, circadian sleep-wake rhythm disorder) with improvement in the difficult behaviour following treatment of the sleep disorder. (15) Upper airway obstruction (including OSA) illustrates important differences between children and adults not only in the clinical manifestation of a particular sleep disorder but also in the underlying cause and treatment needs. Similarly, the early manifestation of narcolepsy in childhood may be very far removed from the classical narcolepsy syndrome in...

Main sleep problems sleeplessness

The revised International Classification of Sleep Disorders (ICSD-R) was outlined in Ch.a.ptei 4. 1.4 1. This system has much in its favour but it is primarily based on the sleep disorders seen in adults. Its overall structure is appropriate for use with children but only some of the disorders described are relevant to them. The point has already been made that various aspects of basically the same disorder can be very different in children compared with adults. This important point is not made clear in the ICSD-R, as it stands. In keeping with the earlier accounts of sleep disturbance in adults, the following selective account of sleep disorders in children and adolescents is organized according to the three main types of sleep complaint sleeplessness, excessive sleepiness, and the parasomnias. Childhood psychiatric and medical conditions in which sleep disturbance is a prominent feature have already been mentioned. The emphasis is placed on the differential diagnosis of sleep...

Phase Shifting Effects Of Melatonin

Following an acute dose of melatonin (0.5-10mg) core body temperature declines and causal links have been suggested between this effect, the induction of sleepiness and, in the case of early evening administration, a subsequent phase advance of melatonin onset and or core body temperature (23,24,25). Substance has been added to this speculation by the observation that both the temperature decline and the sleepiness are dependent on posture (26). Subjects who remain upright and or active after the dose do not show either the sleepiness or the temperature drop. However the induced phase shift may not depend on changes in core temperature. In early work, subjects taking 2mg melatonin daily at 1700h for 30 days and remaining active only showed significant evening sleepiness after 4 days as a group (22,27) and rarely slept in the early evening. Moreover in conditions where very little acute change in temperature was found, phase shifts still occurred (22,27). Fast release melatonin (0.5...

Synchronisation Of Human Circadian Rhythms By Melatonin

Since melatonin does show the characteristics of a zeitgeber in that a PRC can be generated, it would be expected to entrain fully the circadian clock in suitable circumstances. Human tau is on average 24.3 h or less in constant dim light (34,35,36) and thus the clock needs to be phase advanced on average by 0.3 h or less each day. Acute phase shifts induced by melatonin in an entrained or free running environment are of at least this magnitude when sleep is permitted. However it has proved impossible so far to demonstrate entrainment in humans, with the exception of apparent entrainment or stabilisation to 24h of the sleep wake cycle (30,37). Given to blind subjects free running in a normal environment a pharmacological dose of melatonin induces phase shifts (38) and can stabilise sleep onset in some subjects (39,40). There is no good evidence for entrainment of strongly endogenous rhythms such as core temperature and endogenous melatonin itself (30,39). It is possible to maintain...

Complex Effects Of Melatonintheoretical Interpretations

If humans remain photoperiodic, some of these effects of melatonin may be explicable. Animal data (42,43) and some human evidence (44,45) show that extending the night length can lead to a bimodal pattern of sleep activity and sometimes of the endogenous melatonin profile itself. Classical photoperiodic theory attributes this bimodality to two theoretical oscillators, the evening (E) and morning (M) components of a rhythm (42,45). Expansion of a rhythm such as sleep or, in rodents, activity in short days (i.e. long nights) is postulated to be due to an advance of the E and a delay of the M oscillators. Melatonin given only in the early evening (advancing the perceived onset) would be expected to differentially affect these theoretical rhythm generators such that the E is influenced more than the M (or vice versa if given in the morning). The possible differential effect of evening melatonin on melatonin onset (27,31) and, to some extent, on the timing of sleepiness alertness (22),...

Melatonin Treatment Of Winter Depression

In the winter of 1996-1997, it was shown that melatonin (0.125 mg) given at CT 8 and CT 12 was more antidepressant than placebo, in a parallel study with five patients in each group (59). In the winter of 1997-1998jthe dosing regimen was changed to 0.1 mg at CT 8,10 and 12 compared to CT 0,2 and 4. In addition, there was also a placebo group. This was also a parallel study and included 26 patients. As in the first study, most if not all of the responders were in the afternoon melatonin group. Morning melatonin caused a phase delay of the DLMO and afternoon melatonin caused a phase advance. These patients seem to be exquisitely sensitive to the dose-dependent soporific side effect of melatonin. Consequently, the dose had to be lowered quite a bit in these patients. Since, according to the melatonin PRC, the earlier in the afternoon melatonin is given the greater is the resulting phase advance, a second or third dose was given to provide continuously elevated melatonin levels through...

Melatonin As A Marker For Circadian Phase Position

The circadian rhythm of melatonin production turns out to be perhaps the best marker for circadian phase. Its standard deviation is less than that of the temperature rhythm (28). A constant routine is not necessary for its assessment, although sample collection should be done under dim light (< 30 lux). It can be assessed using blood, saliva or urine, although the latter is difficult to collect in intervals shorter than 1-2 hours, and the more frequent the collection intervals the more highly resolved the phase marker. Frequent sampling around the time of the melatonin onset may turn out to be the most useful of all of the markers for circadian phase. The melatonin onset is a clearly demarcated event (Figure 2). With 30-minute sampling, the standard deviation of the dim light melatonin onset (DLMO) is less than its sampling interval (28). The DLMO usually occurs before bedtime consequently, there is little or no disturbance of sleep. Confining measurement of the endogenous melatonin...

Melatonin Role and Circadian Rhythms in Children with OSAS

Melatonin is produced by pineal gland. Light inhibits its secretion. Hence, a rhythmical secretion pattern is seen in all species, including humans. In humans, the highest melatonin levels are found in 2- to 5-year-old children from that age, secretion decrease progressively (Waldhauser, Weiszenbacher, and Tatzer 1988). It has long been known that melatonin has sleep-promoting properties and regulates the sleep-wake cycle. Melatonin has a strong circadian rhythm with high values during the nighttime and low values in the afternoon. Sleep disorders impair the quality of life for children with neurodevelopmental disabilities and their families. Melatonin, a natural regulator of sleep, may be an effective therapy in this area (Wassmer and Whitehouse 2006). Sleep a disordered breathing may change the circadian rhythms of melatonin, which may have diagnostic implications. One major feature in patients with OSAS is EDS chiefly resulting from disturbed sleep at night. It has been shown that...

Relation Between Sleep Apnea and Insomnia

Insomnia and OSA are the two most common sleep disorders and yet peer-review publications based on state-of-the-art, evidence based literature are lacking in describing the interaction and implications emerging from the inter-relationship between the two. This has been well addressed in an editorial by Krakow (33). Insomnia is generally considered an infrequent presenting night-time complaint in patients with OSA. Yet review of limited literature shows a higher percentage than generally believed. In a retrospective study by Krakow et al. (34) 50 of patients with PSG-proven SDB, reported significantly problematic insomnia symptoms. More recently, Smith et al. (35) using a rigorous methodology reported a prevalence of significant insomnia in 39 of PSG-proven patients with OSA. Women with OSA are more likely to have insomnia than are men with the same degree of OSA (36). Looking at the reverse picture, what is the prevalence of SDB in insomnia patients Research shows that these numbers...

Chronobiotics And Insomnia Therapy 21 Definition of Chronobiotic

MLT may be an internal zeitgeber (7,8) and as a rule of thumb, its effects on cir-cadian timing are the opposite to that of light i.e. when light phase advances a rhythm, MLT administration phase delays and vice-versa. Since the ability of MLT to entrain rat circadian rhythms depends upon the integrity of the SCN (17) and since both the rodent and human SCN contain high affinity MLT receptors (50,69), it would be reasonable to expect that exogenous MLT administration should be therapeutic for treatment of circadian insomnias. With respect to MLT and treatment of circadian sleep disorders, the chronobiotic properties of the substance should be distinguished from its soporific hypnotic effects

Melatonin Receptors As Therapeutic Targets

Molecular and pharmacological studies suggest the presence of melatonin receptors in the human central nervous system. Melatonin receptors were localized to the human suprachiasmatic nucleus and to the molecular layer of the cerebellum by receptor autoradiography with 2- 125I -iodomelatonin (19,21). In postmortem human cerebellar membranes 2- 125I -iodomelatonin binds to a site showing pharmacological characteristics similar to those of the human mt1 melatonin receptor (24,39). Both mt1 and MT2 mRNAs have been amplified from human tissues using reverse transcription polymerase chain reaction. The mt, mRNA was localized to the suprachiasmatic nucleus and retina and the MT2 to the retina, hippocampus and whole brain (8,21,23). Using in situ hybridization histochemistry, the mt1 melatonin receptor was localized to the suprachiasmatic nucleus and to the granule cell layer of the cerebellum of human postmortem brain (21,48). Recently, we demonstrated the localization of MT2 mRNA to human...

Sites Of Action Of Melatonin 41 Melatonin Receptors

In situ autoradiography using 2-(125I)iodomelatonin as a ligand has been used to map the distibution of putative melatonin receptors in the ovine brain and pituitary gland with the aim of identifying target sites for the action of melatonin (Figure 2). Specific, high affinity binding of melatonin has been demonstrated in many sites in the hypothalamus, limbic system and brain, with highest levels of binding in the pars tuber-alis of the pituitary gland (5,20). Using in situ hybridization with a specific probe for the melatonin receptor (mtl receptor) melatonin receptor gene expression has been demonstrated in the pars tuberalis zona tuberalis of the ovine pituitary (62,69), but not in the brain sites indicated by binding studies. This may reflect a lower of expression in the neural sites, or the presence of another form of receptor. The latter possibility is indicated by failure to find a transcript corresponding to the mt1 receptor in hypothalamic RNA extracts amplified by RT PCR (P....

Melatoninand Reproduction

A major physiological role of melatonin in adult mammals is the regulation of seasonal reproduction (for reviews see 3,21,33,68 and this volume). The pineal gland is necessary for appropriate perception of seasonal changes in day length and thus for the proper timing of reproduction in species which breed seasonally. The duration of the nocturnal melatonin elevation is regulated by the photoperiod. Melatonin ultimately affects reproductive activity by modulating the activity of hypothalamic neuroendocrine circuits whose activity is necessary for gonadal function. In the broadest Figure 2. The maternal pineal gland is the source of melatonin rhythms in fetal sheep. Top panel Melatonin rhythms in the mother and fetus are similar in phase and amplitude. Lower panel Removal of the maternal pineal abolishes maternal and fetal melatonin rhythms. Modified from Ref. 87. Figure 2. The maternal pineal gland is the source of melatonin rhythms in fetal sheep. Top panel Melatonin rhythms in the...

Sources Of Melatonin During Development

The primary source of circulating melatonin in adult mammals is the pineal gland (38). Melatonin levels are elevated at night. As reviewed in detail elsewhere in this volume, melatonin production from the pineal is regulated by the circadian clock in the suprachiasmatic nuclei. Other tissues appear capable of producing melatonin. Melatonin is produced rhythmically in the retina, but the retina does not appear to contribute significantly to circulating melatonin levels in rodents. N-acetyltransferase activity and NAT gene expression occur in other tissues, including brainstem and pituitary (12). With precursor loading it is possible to detect significant production of melatonin in the gastrointestinal tract, although melatonin synthesized in the gastrointestinal tract does not appear to contribute to circulating levels of the hormone (24). It is nevertheless possible the local production of melatonin within the abdomen may provide a pool capable of reaching the fetus. The primary...

Proposed Autonomic Regulation Of Melatonin Syntheis By Glutaminergic Systems

Based on these observations, we concluded that rat pinealocytes are equipped with machineries for input, output and termination of the glutamate signals (Fig. 1). Since the same pinealocytes express all these glutaminergic elements, the glutamate may be used as autocrine- or paracrine-like signals in the endocrine organ upon stimulation, pinealocytes secrete L-glutamate so as to inhibit NE-stimulated melatonin synthesis. Excess amount of glutamate is rapidly taken up by the reuptake system(s). Thus, melatonin synthesis in pinealocytes is negatively regulated by the glutaminergic systems. The glutamate-evoked regulation of melatonin synthesis seems to be a novel type of hormonal regulation, because a classical neurotransmitter is involved in the hormonal synthesis. Now, we are trying to reveal the elements of the pineal gluta-minergic systems at the molecular level. The glutamate-evoked inhibition of melatonin synthesis is observed even in the presence of NE, indicating that the...

Melatonin Biosynthesis In Chicken Retina

The retinae of many vertebrates have the capacity to synthesize melatonin (44). However, this source of melatonin does not appear to contribute substantially to circulating melatonin, which is pineal derived. Retinal melatonin appears to act locally as a paracrine neuromodulator and regulator of rhythmic retinal physiology (21,23). Retinal melatonin is synthesized primarily in photoreceptor cells (2,10,17,18,42) and its production is regulated by a local, retinal circadian clock (4,10,41). Melatonin modulates the release of several neurotranmitters in the retina. It inhibits the release of dopamine (6,13) and acetylcholine (29) from amacrine cells. Melatonin stimulates the release of glutamate (15), the photoreceptor neurotransmitter. The release of dopamine and acetylcholine are stimulated by light (e.g., 5,27), while glutamate is released from photoreceptors in darkness (e.g., 34). Thus, melatonin mimics, and may partiially mediate, the effects of darkness on neurotranmitter...

Vascular Effects Ofmelatonin

There is now compelling evidence that melatonin acts directly on blood vessel receptors in certain vascular beds, such as the brain, heart and skin. Initial autoradiographic studies using 2- 125I iodomelatonin indicated a restricted localization of vascular melatonin receptors. Specific binding was detected in cerebral and tail (caudal) arteries, but not in other arteries of the rat, including the aorta (53). Both vasoconstrictor and vasodilator effects have been reported for melatonin in isolated arteries, and recent studies have begun to elucidate the underlying receptors and mechanisms. The function of vascular melatonin receptors has been studied mainly in the rat tail artery, a thermoregulatory vessel. In isolated tail arteries, nanomolar concentrations of melatonin produce constrictor effects and the pharmacological characteristics of the response are consistent with known melatonin receptors (21,25,35,50,53, see below). Vasoconstrictor responses to melatonin also have been...

Melatonin As A Phaseresetting Agen

In some animals, exogenous melatonin causes phase shifts and can even provide an entraining signal (see above). Early work by Arendt suggested that melatonin could intermittently have phase-advancing effects (48). Blind people appear to be even more sensitive to these effects than sighted people, perhaps because they are not affected by a competing light dark cycle (49-51). Eventually, a melatonin PRC (four days of administering 0.5mg) was described in sighted people that for the first time 1) showed consistent and robust phase advances 2) demonstrated phase delays and 3) described the relationship between the time of melatonin administration and the direction of phase shift (52). These phase shifts were smaller in sighted people, because melatonin had to override the effects of a light dark cycle which was held constant. The magnitude of these phase shifts increases ten-fold when the sleep wake and ambient light dark cycles are shifted 12 hours (53), as is the case with the light PRC...

Sleep disorders mistaken for psychiatric conditions

Sleep disorders manifest themselves in many ways. Failure to realize this can result in the misdiagnosis of primary sleep disorders as primarily psychiatric conditions. Prominent examples of this mistake are seen in the circadian rhythm sleep disorders. These disorders are also important causes of insomnia (see Chap.teL,4,1.4,2.) and or excessive daytime sleepiness (see Chap.teL,4,1.4,3). Therefore they can also be important in the aetiology of psychological dysfunction caused by sleep disturbance. Collectively, circadian rhythm sleep disorders are common. They are caused either by malfunction of the endogenous systems (the 'biological clock' described earlier) involved in the regulation of sleep-wake rhythm, or by environmental effects on these systems (as in jet lag or shift work). Because of their basically biological nature, this group of sleep disorders requires treatment to produce physiological readjustment to the basic sleep-wake mechanism (e.g. chronotherapy schedules,...

Estimated Therapeutic and Loael Doses of Melatonin

Melatonin is characterized in this book as an immune stimulant (see Table 1.2), but in addition to immune effects it may also have direct cytotoxic effects against TABLE 22.11 ESTIMATED THERAPEUTIC AND LOAEL DOSES FOR MELATONIN* cancer cells. Therefore, it is interesting to compare doses scaled from animal and human experiments to those calculated from pharmacokinetic and in-vitro data. These doses are in agreement. The required mela-tonin dose from the animal experiments is 10 to 50 milligrams per day, the same as the range used in human studies most of these used 10 to 20 milligrams. The anticancer dose based on pharmacokinetic calculations is similar. As discussed, a 10-milligram dose will produce an average nighttime melatonin concentration of about 14 nM, which is reasonably close to the 1-nM optimal concentration. Under normal circumstances, this 1-nM concentration can be reached in vivo with no external administration of melatonin. Thus pharmacoki-netic calculations suggest...

Roles Of Tph And Aanat In Regulating Melatonin Biosynthesis

The dramatic nocturnal increase of melatonin biosynthesis involves the induction of both TPH and AA-NAT. Similar to the situation in Xenopus retina (9), administration of the serotonin precursor, 5-hydroxytryptophan (5HTP), at night greatly increases chick retinal melatonin levels (Figure 6). Administration of tryptophan has no effect. This observation indicates that AA-NAT is not saturated with substrate in situ, and that the induction of TPH at night contributes to high rates of melatonin biosynthesis by increasing the supply of serotonin to AA-NAT. In contrast, adminstration of 5HTP during the daytime, when AA-NAT activity is low, elicits a relatively small stimulation of melatonin level (37). Similarly, little increase of melatonin level is observed following 5HTP administration after acute light exposure at night, which suppresses AA-NAT activity (Fig. 6). Accordingly, it is clear that AA-NAT plays a primary role in regulating melatonin production, and that large changes in...

Effects Of Melatonin On The Growth And Linoleic Acid Metabolism Of Hepatoma 7288ctc

We initially determined the sensitivity of hepatoma 7288CTC to the oncostatic effects of pharmacological doses of melatonin (50 to 200 (g) injected S.C. into tumor-bearing rats, maintained on a 12L 12D light dark cycle, every afternoon one to two hours prior to lights off (PM). Injections with melatonin or vehicle began one week prior to tumor implantation and continued until the end of the experiment three to four weeks later. Melatonin treatment was effective in delaying the appearance and suppressing the growth of hepatoma 7288CTC at all doses tested. Furthermore, the tumor uptake, content and release of linoleic acid, total fatty acids and 13-HODE, respectively, was suppressed in animals receiving PM melatonin therapy in a dose-dependent manner. Interestingly, in a study in which melatonin (200 (g to 1mg) was injected in the morning (AM) two to three hours following lights on, there was no effect on tumor growth or linoleic acid uptake and metabolism (6-8 unpublished results)....

Insomnia in Aging Influence on Immunity

Normal healthy aging is associated with increasing sleep fragmentation, increasingly light sleep (stages 1 and 2), and less slow wave sleep (SWS, stages 3 and 4) (Benca, Obermeyer, Thisted, and Gillin 1992 Ehlers and Kupfer 1997 Van Cauter, Leproult, and Plat 2000). These changes are thought to contribute to daytime fatigue, depression, and impairments in health functioning in older adults. Such changes in sleep parameters may explain why self reported poor sleep is one of the most common complaints in elderly adults. Furthermore, the elderly are at higher risk of developing insomnia than any other age group, and this sleep impairment is independent of medical and psychiatric illness, medication use, circadian rhythm changes, and psychosocial factors which can all contribute to sleep complaints (Ancoli-israel 2000). As of yet, there are no studies integrating cytokine and sleep assessment in older adults with insomnia. Considering that older adults are particularly vulnerable to...

Melatonin In Prenatal Development Hormone Or Pheromone

Melatonin And Estrogen Receptor

Briefly consider the perceptual world of the fetus. Consider the role the mother plays in sheltering the fetus from the external environment. In this context, it seems remarkable that the mother is also actively involved in transferring environmental information to the fetus. During gestation, the mother generates signals which allow the fetus to perceive the length of the light portion of the lighting cycle (day length) as well as the phase (timing) of the light-dark cycle. We refer to these two different forms of prenatal communication as maternal-fetal communication of daylength and maternal-fetal communication of circadian phase, respectively (Figure 1). The maternal melatonin rhythm appears to play a role in transmitting both attributes of the lighting cycle from mother to fetus. Melatonin is thus an important component of the perceptual world of the fetus. In this context, it may be worth considering melatonin as a pheromone (a chemical substance from one member of a species...

Immune Function in Sleep Disorders

Insomnia and obstructive sleep apnea are the most prevalent sleep disorders in the general population (Ancoli-Israel 1993). Such disturbances result in major alterations in the immune system and may be mediated by the augmented activity of the HPA axis and or sympathetic nervous system, as we will soon describe. There is evidence of the association of insomnia and elevated HPA axis activity. Primary insomnia patients connect the onset of the disorder to some stressful event. Chronic internalization of feelings may cause a psychological and physiological arousal, leading, ultimately to insomnia. Perlis, Giles, Mendelson, Bootzin, and Wyatt (1997), for instance, propose the existence of a mechanism of cortical hyperarousal in insomniac patients triggered by emotional, cognitive, and physiological components. Therefore, the hyperactivity exacerbates vigilance and impact negatively on sleep, thus forming a vicious circle in which difficulty to sleep becomes the stressful factor itself....

Decoding The Melatonin Signal

Melatonin Receptor

The ovine pars tuberalis has become a valuable pharmacological model for studying the function of the melatonin receptor, not only as it is amenable to cell culture and biochemical experiment, but also as it is a photoperiodically relevant target tissue. Using primary cultures of this gland it has been possible to define the acute signal trans-duction characteristics of the melatonin receptor. Reverse transcription PCR, using degenerate primers, has been used to amplify melatonin receptor sequences from mRNA extracted from ovine pars tuberalis (oPT), and only the Mella (mti) receptor sub-type has been amplified, although we have found that this exists in two allelic forms (GenBANK accession number AF045219) (1). We have also amplified, cloned and sequenced an ovine melatonin-related receptor, which does not bind melatonin, from the ovine pars tuberalis (3), yet we have found no evidence for a sheep Mellb (mt2 receptor in this tissue or from genomic DNA (1) (unpublished observations)....

Melatonin Aging And The Circadian System

Aging is associated with a number of changes in the morphology, physiology and biochemistry of the pineal gland resulting in a significant reduction of the nocturnal melatonin levels in rodents and humans alike (12,20,27). It has been hypothesized that the age-related disruption of this robust signal affects the integrity of circadian time structures and is a precursor of disease states (2,21). Recent studies indicate that decreased binding of melatonin to the SCN of old rats is correlated with disruption in overt circadian rhythmicity (43), whereas treatment with the melatonin agonist, S-20242, can partially reverse the age-related decrease in the amplitude of the circa-dian temperature rhythm (13). We have recently found that in some hamsters treatment with melatonin in the food increases the amplitude and cohesiveness of the rhythm of locomotor activity which often becomes fragmented and disorganized in old animals (Van Reeth, unpublished results). Further support for some linkage...

Direct Effects Of Melatonin On Tumor Linoleic Acid Uptake And Metabolism And The Signal Transducton Mechanisms Involved

In the tumor growth experiments cited above, it was not completely clear whether the inhibitory action of melatonin on tumor growth was the result or cause of the inhibition of linoleic acid uptake and its conversion to 13-HODE. To more precisely address the question of whether melatonin directly inhibits tumor fatty acid uptake and metabolism, we perfused tissue-isolated hepatoma 7288CTC in situ with melatonin. Following a 60 minute perfusion with donor whole blood from 48-hr fasted rats with elevated circulating fatty acid levels, melatonin was added to the whole blood perfusate at near physiological nocturnal peak levels. Approximately 40 minutes following the addition of melatonin to the perfusate, linoleic acid uptake decreased by nearly 70 from the steady-state control perfusion levels. Over this same time-course, tumor 13-HODE production declined to undetectable levels in response to tumor perfusion with melatonin. The suppressive effects of melatonin on linoleic acid uptake...

REM sleep behavior disorder RBD

Patients suffering from RBD enact their dreams and nightmares during periods of REM sleep devoid of the physiological muscle atonia. They show purposeful hand and arm movements which are sometimes violent and may lead to injuries of the patient or their bed companion. They talk, shout, fall out of bed, but only rarely do they walk like sleepwalkers do when emerging from slow wave sleep. Such RBD can be observed in all types of parkinsonism, whether they result from synucleinopathies (affecting one third of PD patients and almost all patients with Lewy body dementia or multisystemic atrophy), tauopathy, as in supranuclear palsy (Arnulf et al., 2005), or Parkin gene mutation (Kumru et al., 2004). In one quarter of the patients, this behavior disorder has heralded other symptoms of PD by 5 to 10 years. The lesion responsible for RBD is unknown, but lesions of the locus subcoeruleus in the pontine teg-mentum led to typical RBD (initially named ''oneiric behavior'') in animal models of RBD...

Melatoninwithout The Hype

The melatonin project was started at Yale by Dr. Yoshiyata Takahashi and me, and completed nearly 4 years later by Dr. James Case and me. In our investigations on normal and malignant pigment cells we were studying the action of humoral and neural factors on the dispersion and aggregation of melanosomes in frog melanocytes. My research was on pigmentation at basic and clinical levels. We had just completed the isolation of a melanocyte-stimulating hormone (MSH) a dispersing factor from the pituitary gland. We were intrigued by a paper by McCord and Allen in 1917 in which they claimed that extracts from bovine pineal glands lightened that is, had an aggregating action on the color of tadpoles. We had already studied the aggregating action of adrenaline, noradrenaline and acetylcholine. Was the agent in the pineal gland of these neural chemicals We decided to find out. No one seemed to have been interested in the report by McCord and Allen. We had no competition. Immediately after we...

Melatonin In Denervated Melanophores

Melatonin Receptor

Denervation affects the pigment aggregation response mediated by noradrena-line to become more sensitive and displace the concentration-response curve to the left. Therefore, denervation might then also affect the response mediated by melatonin. Actually, melatonin lost its modulatory effect and became a potent as well as a full agonist (8). Since no functional nerve endings are present in this preparation, that means that the studied receptors have a postsynaptic location. For decades, it has been known that yohimbine is a selective a2-adrenoceptor antagonist, and the compound has been used to characterize adrenoceptors. Yohimbine is an effective antagonist against both noradrenaline and B-HT 920, but with slightly different pharmacological profiles. We originally thought that yohimbine would be the negative control to exclude a2-adrenoceptor involvement in melatonin-induced pigment aggregation. The substance to be tested as antagonist against melatonin, was the ai-adrenoceptor...

Mammalian Melatonin Receptors

Melatonin Receptor Nomenclature and Classification This review will use the nomenclature and classification for melatonin receptors adopted by the International Union of Pharmacology (23) in 1998 (Figure 1). Accordingly, the melatonin receptors are referred to with the letters MT (MelaTonin). This nomenclature uses lower case mt followed by its number to describe receptors for which only the molecular structure is known (e.g., mti former MeL) (8). Melatonin receptors with a well defined functional pharmacology in a native tissue, as well as known molecular structure are referred in upper case followed by a number subscript (e.g. MT2 former MeU) (8,24-25). Upper case in italics (MT) followed by the corresponding number is reserved for receptors pharmacologically characterized in native tissues for which the molecular structure is not known (e.g., MT3 former ML2) (14). 2.2. Melatonin Receptor Subtypes The original classification of melatonin receptors differentiated the ML1 and ML2...

Melatonin Modulation In Innervated Melanophores

Wilcoxon Signed Rank Symbols Images

With the two-site receptor model in mind, we suggest a new possibility melatonin may modulate the a2-adrenoceptor response (4). This hypothesis implies that a hormone and a neurotransmitter can somehow integrate their own signal messengers into a common signal. The question is where does the interaction occur Does it take place on the receptor surface and involve an allosteric site, or does it occur somewhere along the transduction pathway, or at some point during the intracellular process that controls pigment aggregation Melatonin alone has almost no effect on pigment aggregation in melanophores on isolated scales, but it did enhance pigment aggregation that had been elicited via the a2-adrenoceptor. Thus, the effect of melatonin must be dependent on the presence of an a2-adrenoceptor (Figure 3). However, melatonin had the opposite effect when used in combination with B-HT 920 which is another a2-adrenoceptor agonist (Figure 4). Instead of increasing aggregation as with the other...

Sleep Disorders

Director, Stanford Center for Human Sleep Research Associate Professor, Stanford University Medical Center Stanford University Center of Excellence for Sleep Disorders Stanford, California, U.S.A. University of Washington Sleep Disorders Center Harborview Medical Center Seattle, Washington, U.S.A. 1. Clinician's Guide to Pediatric Sleep Disorders, edited by Mark A. Richardson and Norman R. Friedman 2. Sleep Disorders and Neurologic Diseases, Second Edition, edited by Antonio Culebras

Melatonin Synthesis

Melatonin production of the explanted trout pineal organ maintained in perifusion culture is directly regulated by the ambient illumination with low levels in the photopic range and high levels in the scotopic range and in darkness. The effect of light is clearly reduced in the presence of IBMX, a non-specific inhibitor of phosophodi-esterases (PDE), showing maximal melatonin production in dim light. The nitric oxide donor SNAP increases melatonin production in IBMX-treated pineal organs.

Melatonin

The first demonstration in sheep that melatonin secretion from the pineal gland relays effects of photoperiod to time seasonal characteristics was achieved by housing Soay rams under a driving 32-week lighting regimen (28). Under these conditions, sheep without a functional pineal gland (pinealectomised or superior cervical ganglionec-tomised) were shown to be unable to adjust their long-term physiological rhythms to the changing photoperiod, although the intrinsic cyclicity persisted (44). Definitive evidence that the daily rhythm in melatonin secretion from the pineal gland mediates effects of photoperiod was provided from studies in which pinealectomised ewes were treated with programmed infusions of melatonin designed to mimic the normal daily patterns of melatonin secretion (4,6). Short-duration infusions (8-h daily) were found to suppress gonadotrophin (LH) secretion, as normally occurs in pineal intact ewes under long days, while conversely long-duration infusions promoted...

Insomnia

All of the benzodiazepines will produce sedative-hypnotic effects of sufficient magnitude to induce sleep, provided that the dose is high enough. However, the aim in the treatment of sleep disorders is to induce sleep that is as close as possible to natural sleep so that the patient falls asleep quickly, sleeps through the night, and has sleep of sufficient quality to awake refreshed. Extensive sleep studies have been conducted with a variety of sedative-hypnotic drugs, and all of these drugs appear to alter the normal distribution of rapid eye movement (REM) and non-REM sleep. Most of the older sedative-hypnotic agents markedly depress REM sleep. In contrast, when the benzodiazepines are used in appropriate doses, they depress REM sleep to a much smaller extent. As with treatment of anxiety, the choice

Primary Insomnia

Clinical studies with insomnia patients corroborate the sleep-immune findings of partial sleep deprivation, with studies indicating evidence of immune dysregulation. In general, insomniacs show increased levels of inflammatory cytokines (Vgontzas et al. 2002 Burgos et al. 2005) and decreased T-helper (CD3+, CD4+), T-cytotoxic (CD8+) cell numbers (Savard, Laroche, Simard, Ivers, and Morin 2003), and decreased NK cell activity (Irwin, Clark, Kennedy, and Ziegler 2003). Irwin and colleagues (2003) discovered that nondepressed insomniacs had diminished NK cell activity and a trend for less lymphokine activated killer (LAK) cell activity (Fig. 10.1). In this study, insomnia patients also showed increased levels of catecholamines across the night. Prolonged elevations in sympathetic nervous system activity can suppress NK activity (Friedman and Irwin 1997). Thus, heightened autonomic arousal during the night may promote a suppression in innate immunity the following morning (Irwin,...

Circadian Insomnias

Over the last two decades, circadian rhythm sleep disturbances have risen rapidly in prominence as evidenced by their full inclusion and description in the modern International Classification of Sleep Disorders (63). These disorders are classified into six subgroups (NODS is not pertinent)(Figure 1), but can be regrouped in different ways. Previously, we have grouped the disorders according to the type of chronobiotic action required to readjust or synchronize the disturbed rhythm (9). Here, the disorders are first grouped according to natural versus artificial occurrence and second according to the natural occurrence with age. Time Zone Change and Shift Work Sleep Disorder are clearly artificially induced, and will not be dealt with here. Delayed and Advanced Sleep Phase Syndromes (DSPS and ASPS) and Irregular Sleep-Wake Pattern (ISWP) occur naturally while Non-24-Hour Sleep-Wake Disorder can occur naturally or by accident as in many cases of the totally visually impaired. These...

Melatonin Receptors

Melatonin is a highly lipophilic molecule that is capable of diffusing through both cell and nuclear membranes to enter intracellular compartments. Recently, two distinct MLT receptors were identified a cell membrane, G-protein linked receptor, and a nuclear MLT receptor. The membrane-bound MLT receptor was first characterized by Reppert et al. (29), and is termed the MeL (mti) receptor. The mti receptor binds MLT with a Kd of approximately 0.06 nM, and affects cellular activity by transmitting its signal through second messenger G-proteins (30). A second MLT receptor, termed the Meln (MT2) receptor, has also been described. The MT2 receptor binds MLT with an affinity similar to that of mti. The MT2 receptor is also a membrane-associated, G-protein linked receptor with 60 homology to the mti receptor at the amino acid level

Causes of insomnia

Situational stress concerning job loss or problems, or an illness in the family often disrupt sleep. Patients under stress may experience interference with sleep onset and early morning awakening. Attempting to sleep in a new place, changes in time zones, or changing bedtimes due to shift work may interfere with sleep. Exercise or overstimulation late in the day may cause insomnia. B. Drugs associated with insomnia include antihypertensives, caffeine, diuretics, oral contraceptives, phenytoin, selective serotonin reuptake inhibitors, protriptyline, corticosteroids, stimulants, theophylline, and thyroid hormone. C. Psychiatric disorders. Depression is a common cause of poor sleep, often characterized by early morning awakening. Associated findings include hopelessness, sadness, loss of appetite, and reduced enjoyment of formerly pleasurable activities. Anxiety disorders and substance abuse may cause insomnia. D. Medical disorders. Prostatism, peptic ulcer, congestive heart failure,...

Sleep stages

Conventionally, standardized criteria(8) are used to identify different sleep stages according to their characteristic physiological features especially in the electroencephalographam (EEG), electro-oculogram, and electromyogram. REM sleep is physiologically very different. Brain metabolism is highest in this stage of sleep with a low voltage, mixed frequency, non-alpha EEG. Spontaneous rapid eye movements are seen and electromyogram activity is virtually absent in skeletal musculature. Heart rate, blood pressure, and respiration are all variable, body temperature regulation ceases temporarily, and penile and clitoral tumescence occurs. REM sleep usually takes up 20 to 25per cent of total sleep time. Most dreams, including nightmares, occur in REM sleep.

Melatonin Effects

The pineal hormone melatonin is involved in photoperiodic regulations of reproductive functions and in entrainment of daily rhythms. In order to determine general intracellular mechanisms of melatonin action, we have compared melatonin effects in two different cell types. Melatonin acts through the specific high-affinity membrane receptors (K 10-11 M) (22,24,36,38). Distribution of the melatonin receptors has been determined by in vitro autoradiography using 125I-melatonin. Melatonin receptors are present in discrete areas of the rat brain. High density of the receptors has been found in suprachiasmatic nuclei of the hypothalamus, in area postrema and in pars tuberalis of the pituitary (23,37). The receptor density in the rat pars distalis is age-dependent it is about 30 fmol per mg of protein on embryonic day 20 and postnatal day 1, but within 30 postnatal days decreases 10 times, i.e. below 3 fmol mg protein (23). We have studied melatonin effects and their intracellular mechanisms...

The Role Of Nacetyltransferase In Regulating Rhythms In Pineal Indole Metabolism

I learned more about melatonin primarily from articles by Axelrod's group, especially those that were coauthored by Dick Wurtman (12,25-27).These convinced me that there were lots of interesting open questions in the area. With Raisz's generous support and encouragement, I started to study melatonin. seemed quite happy. They made melatonin from radiolabeled precursors and responded to norepinephrine (13,30), as had been reported by Axelrod and Wurtman, working with Harvey Schein (31). The melatonin response was robust, about 10-fold. My initial goal was to demonstrate that this was accompanied by an increase in HIOMT activity which would confirm the then popular HIOMT hypothesis. However, norepinephrine treatment didn't increase HIOMT activity (13). Similarly, I discovered that dibutyryl cyclic AMP elevated melatonin production without increasing HIOMT activity (32), which provided more reason to question the role of HIOMT in regulating melatonin production. I was faced with a puzzle....

Functional Aspects Of The Phylogenetic Transformation Of Pinealocytes

As can be expected from the structural transformation of pinealocytes in the course of evolution, also the receptor mechanims and signal transduction cascades regulating melatonin biosynthesis show striking interspecific variation. In the pineal organ of poikilothermic vertebrates and birds, melatonin biosynthesis is regulated through light stimuli perceived by true or modified pineal photoreceptors. In most of these non-mammalian species (e.g., lamprey, zebra fish, pike, house sparrow) pineal melatonin biosynthesis is also under control of an endogenous oscillator which resides in the pineal itself and is capable of generating endogenous (circadian) rhythms in the absence of any environmental cue. The pineal organ of mammals contains at least in adult individuals neithefunctional photoreceptors nor endogenous rhythm generators. Here, the melatonin biosynthesis is regulated through signals from the retina as photoreceptor organ and the suprachiasmatic nucleus as endogenous oscillator....

Regulation Of Tph And Aanat Expression Andactivity

AA-NAT mRNA is localized primarily to the photoreceptor layer of the chick retina, with a lower level of expression in the ganglion cell layer (2) expression was not detected in the inner nuclear layer. TPH mRNA expression is also strong in the photoreceptor layer (12). In addition, TPH mRNA is found in the ganglion cell and inner nuclear layers. The localization of TPH mRNA alone (without AA-NAT mRNA) in the inner nuclear layer corresponds to the previously described serotonin-immunoreactive amacrine cells (28,39). Expression of both mRNAs in photoreceptors is consistent with this cell type as the primary source of retinal melatonin. Localization of TPH and AA-NAT mRNAs in the ganglion cell layer is unexpected, as serotonin immunoreactivity has not been observed in this cell layer of chick retina. This observation suggests that some ganglion cells may synthesize melatonin or N-acetylserotonin. However, the available evidence suggests that melatonin synthesis in ganglion cells is not...

Microvesiclesmedicated Glutamate Exocytosis Glutamate Signal Output

Taken together, we concluded that pinealocytes can fire glutamate signals with a similar mechanism as in synapses. The internal concentration of glutamate in MVs reaches around 50mM, which might be high enough to inhibit melatonin synthesis (see below) even after suitable dilution through exocytosis.

Glutamate Signal Input

Exogenous L-glutamate reversibly inhibited both NE-stimulated melatonin synthesis and NAT activity with the concentration required for 50 inhibition being 85 M (16). The inhibition was not observed with D-glutamate or its metabolites such as y-aminobutyrate (GABA) (14), but observed with D, L-aspartate (17,18), supporting that receptor-mediated glutamate signaling is involved in the inhibition. To define the role of glutamate in pinealocytes, we investigated a signal transduction pathway by which glutamate inhibits melatonin synthesis in rat pinealocytes. Pharmacological analyses with agonists for various glutamate receptors (GluRs) were performed to investigate participation of GluRs in this putative glutamate signaling in pinealocytes. It was found that that 1 mM acid (tACPD), (L-CCG-I) and (DCGIV), agonists for class II metabotropic GluRs (mGluRs) (19-22), inhibited melatonin synthesis about 50 as was the case of L-glutamate. No other GluR agonists including N-methyl-D-aspartate...

Transfection ofPinealocytes with ICER Constructs

A partial cDNA of the ICER 5'-end (0.2 kb) was generated by RT-PCR from RNA isolated from rat pineal glands as described earlier (65). The two primers used (forward 5'-TTT-TGG-ACT-GTG-GTA-CGG-CC-3' reverse 5'-GGG GAC TGT GCA GGCTTC CT-3') encompass the start site of translation of the ICER gene (63,45) and the ICER coding sequence upstream the first DNA binding domain. PCR fragments were size-selected, electroeluted, subcloned into the vector pBS SK- and sequenced before further use. Prior to transfection of pinealocytes, the ICER cDNA fragment was subcloned into the eukaryotic expression vector pRc CMV (Invitrogen) in either antisense (pICERas) or sense (pICERs) orientation. As an additional control, cells were transfected with the vector alone (pRC CMV). To monitor transfection efficiency within a given experiment, cells were cotransfected with 10 g of the vector pCH110 (Pharmacia) that carries the -galactosidase gene. Primary pinealocyte cultures were prepared, maintained as...

Adrenergic Receptors in the Membrane ofthe Rodent Pinealocyte

In rodents, norepinephrine (NE) is released nocturnally from the intrapineal nerve endings of sympathetic neurons originating from the superior cervical ganglion (21) and binds to a- and P -adrenergic receptors on the pinealocyte membrane (32). The - and -adrenergic receptors are the predominant neurotransmitter receptors in the rodent pineal organ. Of all rat tissues tested the pineal organ exerts the highest expression of 1-adrenergic receptor mRNA (40). Beside these adrenergic receptors, which are in the focus of this contribution, many other, e.g. peptidergic-, monoaminergic-, and cholinergic receptors are present in the rodent pineal gland as well (61,39). However, the P 1 -adrenergic receptor appears to be most important for AANAT mRNA upregu-lation and stimulation of melatonin biosynthesis (32,61,35).

Conclusion And Perspective

In the rodent pineal organ stimulation of melatonin biosynthesis is tightly linked to activation of P-adrenergic receptors by norepinephrine which elevates intracellular cAMP levels, activates PKA, causes phosphorylation of the transcription factor CREB, and stimulates ICER expression (see above). Our findings that NE-induced melatonin biosynthesis is inhibited by PKA-antagonists, but not by CaMK-, PKC-, or MEK1-antagonists suggest an important role of the for both transcriptional regulation of AANAT and melatonin biosynthesis in the rodent pineal organ. Our in vivo investigations with the rat (Maronde et al. unpublished observations) and the C3H mouse (Von Gall et al., unpublished observations) revealed conspicuous diurnal changes in the amount of pCREB and ICER protein related to AANAT expression in both rodent species. Thus, our in vitro observations apparently mirror physiologically relevant changes occuring under in vivo conditions.

HPD Animals Treated with GnRH

The HPD Soay ram model has also been used to assess whether melatonin acts in the pituitary gland to affect gonadotrophin secretion (38). This has involved treating HPD rams with a standard pulsatile infusion of GnRH to reactivate the gonadotrophin testicular axis in animals exposed to long and short days (different melatonin signal, Figure 6). The replacement of GnRH is necessary since the HPD surgery destroys the terminals of the GnRH neurones and blocks the endogenous GnRH drive to the gonadotrophs which become quiescent (12,43). The chronic treatment with pulsatile GnRH for 10 weeks induced an increase in LH and FSH secretion, and full maturation of the testes in HPD rams, but there was no effect of the prevailing photoperiod on these reproductive responses. This was despite differences in prolactin secretion between the groups. These results support the conclusion that mela-tonin does not act in the pituitary gland to affect GnRH-induced gonadotrophin secretion, and the changes...

Implant and Lesion Experiments

The simplest interpretation of the experimental studies using the cerebral microimplants and the HPD model is that the melatonin signal that transduces the effects of photoperiod acts at different sites to regulate gonadotrophin and PRL secretion. The caudal region of the MBH appears to be the principle site for the control of gonadotrophin secretion, while the pars tuberalis pituitary gland appears to be the principle site for the control of PRL secretion. The initial observation that microimplants of melatonin placed in the MBH simultaneously affects both FSH and PRL secretion (Figure 3), is therefore explained by the diffusion of melatonin from the implant to the two closely adjacent control sites. In the MBH, the increased exposure to melatonin activates gonadotrophin secretion, while in the pituitary gland the same change supresses PRL secretion. This produces the inverse relationship between the two endocrine systems which is such a notable feature in sheep seasonality (e.g....

Two Different Systems

The concept that melatonin acts via different transduction pathways to affect gonadotrophin and PRL secretion is also consistent with the differences in timing of the endocrine events in relation to manipulations of photoperiod or the administration of melatonin. In sheep, a decrease in blood PRL concentrations can occur within 3 days following an abrupt switch from long to short days (46), while it takes 4 weeks for LH pulse frequency and FSH concentrations to begin to increase (42). In the longer term,

Sites Ancient And Modern

Overall, the data support a simple dual site hypothesis which proposes that melatonin acts independently in mediobasal hypothalamus to affect gonadotrophin secretion but acts in the pituitary gland to affect PRL secretion (Figure 8). Since mammalian species are remarkably similar in the photoperiodic control of PRL secretion it is likely that the melatonin-PRL control mechanism in the pituitary gland has been conserved during the evolution. This may be because all photoperiodic species share common requirement for an endocrine signal of summer. PRL is a pleiotrophic hormone inducing multiple effects on growth and metabolism and may thus consitute such a signal. PRL induces the development a summer pelage, for example, which is a common feature in mammals, and is clearly adaptive. The presence of high concentrations of melatonin receptors in the pars tuberalis in all photoperiodic mammals so far studied (54), is consistent with a generalised role of the pars tuberalis in the regulation...

Results And Discussion

Polyclonal antibodies were raised against a peptide corresponding to the C-terminal region of the Mel 1a receptor (YKWKPSPLMTNNNWKVDSV-COO-, peptide 536) (Figure 1). This region was chosen since the C-terminal of proteins is often considered as more likely to generate antibodies against synthetic peptides than other parts often involved in the folding of proteins (27). Indeed, the selection of a C-terminal peptide immunogen has previously led to the successful production of a number of anti-receptor antibodies including anti-30AR, anti-P2AP, and antibodies against muscarinic acetylcholine receptor subtypes (5,7,28). Furthermore, this sequence shows little or no homology with the corresponding regions of other high affinity melatonin receptors, suggesting little potential cross reactivity with the human Mel 1b subtype and high selectivity for the Mel 1a subtype (Figure 1). Figure 1. Alignment of peptide 536 with carboxy-terminal sequences of melatonin receptors. Single-letter code is...

Conclusionsperspectives

In conclusion, we have shown that Mel 1a receptors selectively couple to Gi2, and Gi3 proteins which likely mediate the inhibitory effect of these receptors on cAMP accumulation. Furthermore, the association between Mel 1a receptors and Gq 11 demonstrates that these receptors are capable of coupling to both PTX-sensitive and PTX-insensitive G proteins. Signalling through Gq 11 proteins either via phospholipase C or other effector systems constitutes promising new candidates for melatonin receptor signalling. In future work, antibodies may also be used to answer questions regarding other properties of Mel 1a receptors. For example, immunoprecipitation and immuno-chemistry with anti-receptor antibodies may be used to localise Mel 1a receptors in tissues and cells from structures known to bind 125I-MLT.

Scn Cells Expressing mt1 Receptor mRna Coexpress Avp mRna In Syrian And Siberian Hamsters

Many animals, especially mammals living in temperate zones, confine life history events to specific times of the year. For example, species of hamsters and voles bred in the long days of spring summer, whereas species of sheep and deer breed in the short days (SDs) of fall winter (1). The most noise-free seasonal cue in their environment is the photoperiod (10). The photoperiod triggers, seasonal responses, including changes in reproductive status mentioned above, as well as cycles of body mass and fat and pelage (1). This photic information is transmitted to the pineal gland via a multi-synaptic circuit beginning with the retina and concluding with the pinealocytes (5). Among the central nervous system structures included in this circuit is the suprachiasmatic nucleus (SCN) of the hypothalamus, the predominant biological clock. The pineal gland, through its primary hormone melatonin (MEL), triggers these and many other seasonal responses (1). MEL is synthesized and released only...

Reentrainment Of Locomotor Activity And Expression Of mPer1 mRna To Successive 8Hr Advanced Ld Cycle

As described above, we found that the drinking-water administration of mela-tonin ameliorated the delay of re-entrainment to an 8-hr advanced LD cycle in both SAMP8 and SAMR1. Thus, melatonin may accelerate the re-entrainment to LD shifts in mice, as observed in melatonin-containing tube-implanted rats (8). However, we do not know whether the melatonin-induced acceleration means the acceleration of an overt rhythm such as locomotion or that of clock gene expression. Expression of mPerl mRNA in the SCN is under the control of the clock genes and this expression is good marker for the circadian rhythm (13). Therefore, we expected to examine the reduction of the mRNA expression of mPerl in the SCN at ZT4 (the peak time of the expression of mPer1 mRNA in normal LD cycle, 13) in successive 8-hr advanced mice. We expected to observe the normalization of the expression of mPerl mRNA at ZT4 in the melatonin-treated animals, because melatonin accelerated the re-entrainment. The experimental...

Competitive Rtpcr Analysis

The effect of melatonin drinking on mPerl expression in the SCN at ZT4 was examined by competitive reverse transcription-polymerase chain reaction (RT-PCR). Control mice of the ddY strain were entrained to a normal LD cycle for 10 days. The mice were then transferred to an 8 hr-advanced LD cycle 3 times with 3-day intervals from Day 2. Some mice were administered melatonin in their drinking water. On the 8 day of the treatment, the mice were sacrificed and their brains were removed and placed in ice-cold saline at ZT4. Slices (0.5 mm thick) of mice brain that contained the SCN were frozen on dry ice and the both SCN were punched out. Total RNA from the SCN (n 4) was extracted by Trizol solution (GIBCO BRL, Gaithersburg, MD, USA). An mRNA selective PCR Kit (Takara, Osaka, Japan) was used for the reverse transcription of approximately 100 ng of RNA, and mPerl and P-actin cDNA were quantified by competitive PCR. PCR reactions were carried out for 18 and 23 cycles for p-actin and mPerl,...

Description and Misdiagnosis

Traditionally, psychophysiological and idiopathic insomnias are divided into three groups depending on the time of wake occurrence sleep onset, sleep maintenance and terminal insomnia. It is now clear that these three types of classic insomnia can be readily confused with the circadian insomnias particularly at the level of primary care physician. Clinical observation suggests strongly that circadian insomnias are far more extensive than hitherto believed. 1.1.1. Delayed Sleep Phase Syndrome (DSPS). In DSPS, sleep onset and wake times occur far later than normal (e.g. sleep 0300 to 1100 hours), there is no difficulty in maintaining sleep once initiated and sleep times are regular from day to day. Enforcing conventional sleep-wake times fails to advance sleep phase. DSPS is easily misdi-agnosed as sleep onset insomnia, hence the extent of the disorder is likely to be more widespread than acknowledged at present. Furthermore, evening-types (owls) who prefer late night retirement may...

Aging Sleep and Endogenous MLT

Low amplitude rhythm in pineal melatonin leads to low circulating nocturnal melatonin levels. 4. Sleep disorder NONE (NORMAL). 1. Low amplitude rhythm in pineal melatonin leads to low circulating nocturnal melatonin levels. 4. Sleep disorder ADVANCED SLEEP PHASE SYNDROME 1. Low amplitude rhythm in pineal melatonin leads to low circulating melatonin levels 3. Sleep disorder IRREGULARSLEEP-WAKE PATTERN_ Against this background, the ability of exogenous MLT administration to reverse circadian phase and amplitude changes and therapeutically improve circadian insomnias can be assessed. The prognosis is good, but the vexing question of pharmacology versus physiology remains.

Irregular Sleep Wake Pattern [ISWP

From the approach taken above (Section 1.1,1.2), ISWP would be found in geriatric humans with highly fragmented sleep, a group not evaluated for MLT therapy. MLT has been tested in the elderly with sleep maintenance insomnia with disappointing results (27). However, these subjects were healthy seniors not geriatrics with diseases, and not reported were the number and duration of individual nocturnal waking and their correlation with endogenous melatonin levels.

Systemiceffects 21 Blood Pressure

Administration of melatonin lowers blood pressure in normal, pinealectomized, or spontaneously hypertensive rats (1 1,26,28,30) as well as in hypertensive patients (3) and healthy young women (7). When infused i.v. into rats, however, melatonin has no immediate effect on either systolic or diastolic blood pressure (43). The hypotensive effect of melatonin may be mediated, in part, through an action on brain areas that regulate blood pressure and sympathetic outflow (11,28,52,54). The known action of melatonin on the suprachiasmatic nucleus would impact both circa-dian and sympathetic regulation of blood pressure (33). In addition, melatonin may influence the release of vasopressin from this nucleus (41). The area postrema of rat brain also exhibits melatonin receptor binding and, interestingly, spontaneously hypertensive rats show a higher density of 2- 125I -iodomelatonin binding in this region as compared to normotensive animals (54).

Other Hemodynamic Effects

Other hemodynamic effects of melatonin have not been well studied. Melatonin appears to have little or no effect on heart rate (7,43,49), although some changes in cardiac function have been reported (4). In vitro, melatonin (0.3 nM) modulated the contractility of rat papillary muscle by counteracting the effects of isoproterenol, and this effect was blocked by N-acetyltryptamine (1). Melatonin may also affect the levels of cholesterol and other plasma lipids (8,20), but again this area needs further investigation.

Contractile Effects in Vitro

Melatonin acts on cerebrovascular receptors to modulate smooth muscle contractility, as shown in studies of rat cerebral arteries, pressurized in vitro (24,3955). Melatonin decreased lumen diameter of middle cerebral artery segments in a concentration-dependent manner (EC50 2.7 nM, Figure 1). This effect was inhibited by luzindole, a competitive melatonin receptor antagonist, and by pertussis toxin pre-treatment (24). The magnitude of the constrictor response to melatonin appears to depend on the level of arterial pressure in vitro responses were greater at higher levels of transmural pressure (24). When compared with other vasoconstrictors at the same pressure, the effects of melatonin were modest relative to those of serotonin, but similar in nature to those of tetraethylammonium (TEA) and charybdotoxin, two blockers of the large conductance, calcium-activated potassium (BKca) channel (24). Smooth muscle BKca channels play an important role in determining arterial tone and are...

Functional Effects in Vivo

Cerebral blood flow was decreased in rats following acute administration of mela-tonin (10). A subsequent study showed that melatonin-induced cerebral vasoconstriction in rats was accompanied by an improvement in the vasodilatory response to hypercapnia (43). In addition, melatonin shifted the lower limit of cerebral blood flow autoregulation to a lower level of arterial blood pressure, thus increasing the security margin for maintaining cerebral blood flow during hypotensive hemorrhage. The authors suggest that melatonin may act on the cerebrovasculature to diminish the risk of hypoperfusion-induced cerebral ischemia.

Constrictor Effects in Vitro

In most isolated preparations of rat tail artery, melatonin does not produce contraction by itself but potentiates the action of other vasoconstrictors (25,35,50,53, Figure 3). However, in pressurized tail arteries from juvenile rats, melatonin could directly constrict the vessel segments (21),similar to what is seen in pressurized cerebral arteries (24). In perfused, non-pressurized tail arteries, melatonin also caused contraction following the addition of NS-1619 to open BK channels (25). We have hypothesized that the varying nature of in vitro responses to melatonin may reflect different resting states of the isolated arterial preparations (25). Evidence suggests the effect of melatonin may depend on factors such as membrane potential, open state of potassium channels, and or levels of cyclic AMP production (9,24,25). Consequently, significant changes in these factors, in vitro or in vivo, would influence the ability of melatonin to elicit a response. Our initial study to...

Role of the Endothelium

Melatonin appears to act on receptors located in the vascular smooth muscle to produce contractile effects (14,16,24,35). Our initial study of tail artery found that mela-tonin potentiated constriction in ring segments lacking an intact endothelial layer (35). However, an additional influence of the endothelium became apparent when we studied cannulated artery segments that were perfused through the lumen (25). We found, to our surprise, that melatonin had no vasomotor effects in this preparation when either the endothelium was removed or endothelial nitric oxide (NO) synthesis was inhibited with L-NAME (NG-nitro-L-arginine methyl ester) (25). Thus, constrictor effects of melatonin in the isolated perfused artery depended on the presence of nitric oxide released by the endothelium. However, melatonin did not affect relaxation responses to either acetylcholine in endothelium-intact arteries or to sodium nitroprusside in endothelium-denuded arteries (25). These findings indicate that...

Conclusions And Potential Clinical Relevance

With the limited data at hand, it is still difficult to discern the overall role of melatonin in vascular regulation. From the few studies which address tissue distribution, it appears that melatonin may target only certain vascular beds. This strategy may allow for local adjustment in the face of global circadian changes in the cardiovascular system. The functional effects of melatonin observed so far in vitro differ among the various vascular preparations examined, however. These findings may reflect different melatonin receptor subtypes, receptor heterogeneity and or multiple cellular targets, different receptor coupling and or signal transduction mechanisms, variations in the resting tone of the vessel and or interactions with endothelial factors or other vasoactive agents. The various possibilities are areas for future investigation. Using rat cerebral and tail arteries, our laboratory has obtained evidence for two receptor-mediated contractile responses to melatonin....

Resultsand Discussion

The effect of melatonin on the NIL (A) and blood plasma (B) AVP levels in sham-operated male rats under immobilization stress (mean S.E.M. n 8-10). Figure 1. The effect of melatonin on the NIL (A) and blood plasma (B) AVP levels in sham-operated male rats under immobilization stress (mean S.E.M. n 8-10). Figure 2. The effect of melatonin on the NIL (A) and blood plasma (B) AVP levels in pinealectomized male rats under immobilization stress (mean S.E.M. n 7-8). Figure 2. The effect of melatonin on the NIL (A) and blood plasma (B) AVP levels in pinealectomized male rats under immobilization stress (mean S.E.M. n 7-8).

Tissueisolated Hepatoma 7288ctc Model System

In this model system, a 3-mm cube of Morris rat hepatoma is attached to and grown on the end of a vascular stalk composed of the truncated superficial epigastric artery and vein in the inguinal region of adult male Buffalo rats. The tumor implant and adjacent pedicle are then enclosed in a sterile parafilm envelope containing penicillin. The arterial supply to and venous drainage from the tumor is thus exclusively via the superficial epigastric vessels. nmor attachment to other host tissues or vasculature is blocked by the parafilm envelope. Following replacement of the tumor implant into the inguinal fossa and closure of the skin, the tumor is allowed to grow in a tissue-isolated manner. This arrangement allows the cannulation of the epigastric vessels for the direct perfusion of the tumor itself with physiological and or pharmacological agents and the measurement of arteriovenous differences across the tumor of various biochemical factors and products important in tumor growth and...

In Vivo Effects ofMLT on Mammary Cancer

Melatonin, the major hormonal product of the pineal gland, has repeatedly been shown to exert a negative influence on the development and growth of hormone-responsive breast cancer (10,11). Most of the work to date on the onco-static effects of MLT in vivo has been conducted in the 7,12-dimethylbenzanthracene (DMBA)- and N-nitroso-N-methylurea (NMU)-induced hormone-responsive rat mammary tumor models. The DMBA model has been studied with respect to the effects of pinealectomy, photoperiod, and MLT administration on the growth and regression of mammary tumors. Blask et al. (10) found that DMBA-induced mammary tumorigenesis is inhibited in light-deprived female rats, and that pinealec-tomy not only prevents this growth inhibition but actually enhances tumor growth. The advantage of the NMU model over the DMBA model is that the growth characteristics of the NMU-induced tumors more closely resemble those of human breast cancer cells. The tumor cells of this model are primarily responsive...

Effects of MLT and atRA on ER and TGFp mRNA Levels

Previous work by our laboratory has demonstrated that MLT can down-regulate the expression of the ER in human breast cancer cells (18), while others have shown that RA also suppresses ER gene expression (59). It has also been shown that both MLT (72) and RA (72) can alter the expression of estrogen-regulated genes, such as TGFP, which are involved in breast tumor cell proliferation. We, therefore, examined the steady state levels of mRNA encoding the ER and TGF-P1 in MCF-7 cells by Northern blot analysis following 48h of treatment with either MLT or atRA alone, or with the sequential regimen of MLT and atRA. Figure 3 shows that both atRA and MLT alone significantly decreased the steady state level of ER mRNA by 62 and 79 , respectively (p < 0.01 vs control). However, the sequential regimen of MLT and atRA reduced ER mRNA expression to almost undetectable levels (p < 0.001 vs MLT or atRA alone). In addition, both atRA and MLT alone enhanced the steady state level of TGF-P1 mRNA by...

Effects ofMLT and RA on NMUinduced Rat Mammary Tumors

The temporal effects of the sequential regimen of MLT and atRA on Bcl-2 and Bak protein expression in MCF-7 cells. MCF-7 cells were incubated with diluent (control) or a regimen of MLT followed 24 h later by atRA (M + atRA) for 1, 2, 3, 4, or 5 days. For each time point, 25 g of total cellular protein per lane was fractionated on 12.5 polyacrylamide gels and transferred to nitrocellulose membranes. Western blots were probed with polyclonal antibodies specific for Bcl-2 and Bak, and proteins were visualized after incubation with a horseradish peroxidase-conjugated secondary antibody and chemiluminescent substrate. Actin protein levels were used to monitor protein loading. Fluorographs from Western blot analyses of the time-course of Bak and Bcl-2 proteins in response to the sequential treatment of melatonin and atRA were quantified by scanning densitometry and normalized to actin protein levels. Results are presented graphically as percent of control (n 3 independent...

More Products

Sleeptracks Sleep Optimization Program Insomnia Buster
Outsmart Insomnia
outsmartinsomnia.com
Wake Up Now

Wake Up Now

For Those Who Can’t Wake Up On Time And Fatigue Throughout The Day. Now You Can Wake Up Early And Be Super Energetic Everyday.

Get My Free Ebook