Modulation of sympathetic neurotransmission by melatonin.
Melatonin is of considerable interest for its regulatory influence on a variety of physiological processes including biological rhythms and neuroendocrine functions. We showed that melatonin potentiates sympathetic neurotransmission in the prostatic portion of the rat vas deferens, by increasing contractions in response to noradrenaline and ATP released by acetylcholine stimulation of presynaptic nicotinic receptors. Melatonin in vitro (100 pg/ml; for 4 h) increased the maximal acetylcholine-induced contraction only when the hypogastric ganglion was present, and this effect was blocked by cycloheximide (100 micrograms/ml). Melatonin also modulated the sympathetic trophic influence on smooth muscle, since it reduced [35S]methionine incorporation into the vas deferens in the hypogastric ganglion-vas deferens preparation. Thus, it is suggested that the regulation of protein synthesis might be one of the mechanisms whereby melatonin modulates endogenous rhythms and synchronizes them to the environmental light cycle.
Carneiro
R C
RC
Department of Pharmacology, University of São Paulo, Brazil.
Toffoleto
O
O
Cipolla-Neto
J
J
Markus
R P
RP
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008715:Methionine / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D014176:Protein Biosynthesis; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects / Q000294:innervation* / Q000502:physiology
D011978:Receptors, Nicotinic; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D008715:Methionine; D008550:Melatonin; D000109:Acetylcholine; D009638:Norepinephrine