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.
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
J
J
Vanecek
K
K
Watanabe
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