Adrenocorticotropic hormone dopamine

Hydroxytryptamine (5-HT), dopamine, and norepinephrine play important roles as central neurotrans-mitters in the process of erection. Still other substances or hormones, such as endorphins, oxytocin, vasopressin, adrenocorticotropic hormone (ACTH) and related peptides, and prolactin, appear to participate in the complex and coordinated process of penile erection. Central nonadrenergic neurons also may influence male sexual behavior. 

D2-like receptors couple mainly to Gi/o proteins, as mentioned above. However, there is no direct evidence to support this coupling for the release-modulating autoreceptors. Moreover, the subsequent intracellular signal transduction has never been studied directly in axon terminals. Mouse AtT-20 pituitary cells, which release acetylcholine and adrenocorticotropic hormone, have been used as a model for axon terminals. When expressed in these cells, D3 receptors mediated inhibition of P/Q-type calcium channels and activation of G protein-coupled inward rectifier potassium channels (Kuzhikandathil et al. 1998 Kuzhikandathil and Oxford 1999). Both would explain the autoreceptor-mediated inhibition of dopamine exocytosis. 

Figure 16.11 Control of catecholamine biosynthesis in the adrenal medulla. TH, tyrosine hydroxylase DBH, dopamine hydroxylase PNMT, phenylethanolamine methyl-transferase ACTH, adrenocorticotropic hormone. The heavy arrows indicate major sites of regulation. (Reproduced by permission from Axelrod, J. Reisine TD. Stress hormones their interaction and regulation. Science 224 452-459, 1984.)...

Nicotine binds selectively to the nicotinic receptors that are present in the adrenal medulla, brain, autonomic ganglia, and neuromuscular junctions. It causes the release of several neurotransmitters and hormones such as acetylcholine, norepinephrine, dopamine, serotonin, arginine vasopressin, j3-endorphin, adrenocorticotropic hormone, and cortisol (187). This neuro-regulatory effect of nicotine is dose-dependent and occurs as plasma nicotine level rises when tobacco is smoked. The neurotransmitters released in the brain medi-... 

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