Melatonin inhibits the increase of cyclic AMP in rat suprachiasmatic neurons induced by vasoactive intestinal peptide.
The effects of melatonin on basal and vasoactive intestinal peptide (VIP)-induced cAMP concentration was studied in dispersed cells of the rat suprachiasmatic nuclei (SCN). Our data indicate, that VIP induces a rapid increase of cAMP concentration in the cells followed by a slow and prolonged increase in the medium. The VIP-induced increase was dose-dependent in the range of 1-100 nM. Melatonin had no effect on basal cAMP but inhibited the cAMP increase induced by VIP in a dose-dependent manner (EC50 = 0.21 nM). Our observations indicate that melatonin acts through the inhibition of cAMP in the SCN cells similar as shown in other tissues.
Vanecek
J
J
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
Watanabe
K
K
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008550:Melatonin / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000166:cytology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D000975:Antioxidants; D014660:Vasoactive Intestinal Peptide; D000242:Cyclic AMP; D008550:Melatonin