Second Messengers II Cyclic AMP cAMP

Rat pinealocytes were shown to contain the alpha-subunits of the G-proteins Gs, Go and Gi (5,6). Their amount did not vary between day and night, but was upregu-lated under stimulus-deprivation, suggesting that these G-proteins may be involved in denervation supersensitivity (5,6). Also the mRNA levels of Gs in the rat pineal gland remain constant at day and night (39; Figure 3). Gs links the activation of the -adrenergic receptors to the activation of adenylate cyclase which causes a drastic increase in intracellular CAMP-concentrations mirrored by a solid increase in extracellular cAMP levels (Co: mean 73 ± 6 fMol/ml; NE for 1 h: mean 1429 ± 226 fMol/ml; SEM; N = 4). Information about the types of adenylate cyclase (AC) expressed in the rodent pineal gland is sparse (70).

C3H Mouse

Time |sec|

Wistar rat

Figure 3. Norepinephrine (1 ^M) causes elevation of the intracellular concentration of free calcium ions in both rat and mice pinealocytes.The response is characterized by a rapid spike followed by a sustained plateau. The abcissa shows the ratio of the intensities of the emitted light at 515nm upon excitation at 334nm and 380nm in single FURA-2 loaded pinealocytes.

Figure 3. Norepinephrine (1 ^M) causes elevation of the intracellular concentration of free calcium ions in both rat and mice pinealocytes.The response is characterized by a rapid spike followed by a sustained plateau. The abcissa shows the ratio of the intensities of the emitted light at 515nm upon excitation at 334nm and 380nm in single FURA-2 loaded pinealocytes.

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