Coccaro et al. (36> found a blunted prolactin response to stimulation with fenfluramine in patients with personality disorders with physical aggression and motor impulsivity. Moreno et al.(3Z) obtained similar results in patients with a borderline personality disorder and impulsive suicidal behaviour, and a blunted response to prolactin after stimulation with clomipramine in pathological gamblers.
Insel et al.(33 observed that behavioural changes (increase in anxiety and obsessive-compulsive symptoms) and physiological changes (variations in body temperature) occurred after the administration of methylchlorphenylpiperazine to patients with obsessive-compulsive disorders. This suggested a hypersensibility to serotonin receptors, compensating a presynaptic function deficit.
Studies by the author's group have provided some clarification of this problem.(3 d04!4 4 and 44 First, unlike patients with impulsive disorders, patients with obsessive-compulsive disorders do not have a blunted prolactin response to the clomipramine challenge test when compared with the control group. However, if the sample of patients is divided according to the depressive symptoms present, those with a pure obsessive-compulsive disorder without depression have a high response to CMI. The presence of a secondary depression produces a blunting of the prolactin response as observed in depressive disorders in general.
Recent research has revealed the impact of social conditions on the neuroendocrine regulation of the individual, particularly with respect to the adaptation to stressful situations. In our sample of patients with a borderline personality disorder and impulsive suicidal behaviour we have found high basal concentrations of cortisol (suggesting a high level of stress) and a very blunted response to the stimulus (suggesting a reduced capacity to respond to external stimulus) compared with the control group. We have found the same pattern in heroin-dependent individuals receiving naltrexone maintenance treatment.
A clue to the interpretation of these results lies in the work of Sapolsky, (45> who has studied the adaptation to stress of baboons in the Serengeti savannah in Africa. Males of a lower rank have consistently high concentrations of the stress hormone hydrocortisone in their blood, whereas the concentration is lower in the dominant males. However, in the dominant males hydrocortisone concentrations increase rapidly at times of stress and decrease once the situation is resolved, whereas the lower-order males, who live in a permanent state of stress, are unable to initiate more adaptive resources (increase hydrocortisone secretion) when new stressful events appear. These patterns are the consequence and not the cause of the rank (if the opposite were true, the baboons who were physiologically better able to respond to stressful situations would achieve a higher rank). During periods of revolution, members of the colony hold successively different ranks and, although there is always one dominant animal, the stability of the society is lost and with it the stress-adapted physiology of the dominant males who show prolonged increased hydrocortisone concentrations like the rest of the group. When calm is established again, the normal pattern related to the hierarchical rank of the baboons is restored regardless of what their cortisol secretion pattern was prior to the revolution.
Impulsivity has been correlated with a low platelet monoamine oxidase ( MAO) activity. Carrasco et al.(46) have studied two groups of professions characterized, at least in principle, by their impulsivity, extraversion, and sensation- and novelty-seeking traits—bullfighters and bomb-disposal officers. They were compared with pathological gamblers and with non-impulsive controls. Their psychological traits were assessed using a series of questionnaires and their platelet MAO activity was measured. The bomb-disposal officers did not differ from the control group, which shows that the process used to select them is very effective. However, bullfighters obtained the highest scores in the traits of impulsivity, extraversion, and sensation-seeking and had reduced platelet MAO activity. Pathological gamblers obtained the highest impulsivity score and the lowest platelet MAO activity of all groups. In addition, the range of MAO concentration in the gamblers was very narrow and all of them showed low MAO activity, whereas in the bullfighters this range was as large as in the controls and many of them had normal values.
This finding suggest that normal impulsive and sensation-seeking behaviours, present for example in the bullfighters, correlate with a diminished platelet MAO activity, which represents a dimensional marker of a temperamental trait. However, in the morbid forms of the behaviour, as in the case of pathological gamblers, the relation with platelet MAO represents a non-dimensional alteration resulting from a pathological change of serotonergic activity, among other factors.
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