title: Physiological concentrations of melatonin inhibit nitric oxide synthase in rat cerebellum.
abstract: In the present paper we show the inhibitory effect of melatonin on rat cerebellar nitric oxide synthase (NOS) activity. NO production was monitored by the stoichiometric conversion of L-arginine to L-citrulline. The inhibitory effect of melatonin was dose-dependent, with an IC50 value of about 0.1 mM. However, a significant inhibition of enzyme activity (> 22%) was observed at 1 nM melatonin which is in the range of the physiological serum concentration of the hormone at night. The inhibitory effect of melatonin was observed exclusively in the presence of Ca++. Results suggest a new and important role of the pineal hormone melatonin on central nervous system processes, i.e., by modulating NO production.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, University of Seville School of Medicine, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Pozo
authors.forename: R J
authors.initials: RJ
authors.lastname: Reiter
authors.forename: J R
authors.initials: JR
authors.lastname: Calvo
authors.forename: J M
authors.initials: JM
authors.lastname: Guerrero
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors*; D000818:Animals; D001120:Arginine / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002531:Cerebellum / Q000187:drug effects / Q000201:enzymology*; D002956:Citrulline / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D019001:Nitric Oxide Synthase; D051381:Rats
chemical_list: D002956:Citrulline; D004533:Egtazic Acid; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D008550:Melatonin; D002118:Calcium