title: Melatonin reduces nitric oxide synthase activity in rat hypothalamus.
abstract: In this report, rat hypothalamic nitric oxide synthase (NOS) activity is shown to be partially inhibited by physiological concentrations of the pineal hormone melatonin. In vitro studies demonstrate that 1 nM melatonin, which approximates the physiological concentration of the hormone at night, significantly inhibited NOS activity. In vivo studies show that administering melatonin or collecting the hypothalamus from animals at night, when endogenous melatonin levels are elevated, results in a significant decrease of NOS activity. Results also show that calmodulin may be involved in this process since its presence in the incubation medium prevents the inhibitory effect of melatonin on NOS activity.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, University of Seville School of Medicine, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Bettahi
authors.forename: D
authors.initials: D
authors.lastname: Pozo
authors.forename: C
authors.initials: C
authors.lastname: Osuna
authors.forename: R J
authors.initials: RJ
authors.lastname: Reiter
authors.forename: D
authors.initials: D
authors.lastname: Acuña-Castroviejo
authors.forename: J M
authors.initials: JM
authors.lastname: Guerrero
mesh_terms: D000818:Animals; D002147:Calmodulin / Q000378:metabolism; D002940:Circadian Rhythm; D003623:Dark Adaptation; D007031:Hypothalamus / Q000201:enzymology*; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D010870:Pineal Gland; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002147:Calmodulin; D019001:Nitric Oxide Synthase; D008550:Melatonin