title: Regulation of melatonin synthesis in rainbow trout (Oncorhyncus mykiss) pineal organs: effects of calcium depletion and calcium channel drugs.
abstract: The effects of calcium depletion and of three calcium channel drugs on melatonin synthesis in pineal organs of rainbow trout (Oncorhyncus mykiss) were examined. Dark-induced melatonin synthesis was inhibited by calcium depletion, by treatment with nitrendipine (NTR), an antagonist of the L-type voltage-sensitive calcium channel, and by treatment with omega-Conotoxin GVIA, an antagonist of the N-type voltage-sensitive calcium channel. Bay K 8644, an agonist of the L-type channel, had no significant effect on pineal melatonin synthesis. These data represent evidence that calcium entry into trout pineal photoreceptor cells through voltage-sensitive calcium channels is important in the maintenance of dark-induced melatonin synthesis and that light's inhibitory effect on melatonin synthesis may be mediated by closure of these channels. NTR-induced inhibition of dark-induced melatonin synthesis was abolished when dibutyryl cyclic AMP (db-cAMP) was administered to NTR-treated pineal organs, suggesting that calcium acts upstream of cAMP in regulating melatonin synthesis.
authors.affiliation: Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82070, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Gasser
authors.forename: W A
authors.initials: WA
authors.lastname: Gern
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000172:deficiency*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D000242:Cyclic AMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008550:Melatonin / Q000096:biosynthesis*; D009568:Nitrendipine / Q000494:pharmacology; D017686:Oncorhynchus mykiss; D009924:Organ Culture Techniques; D010455:Peptides / Q000494:pharmacology; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D020866:omega-Conotoxin GVIA
chemical_list: D002121:Calcium Channel Blockers; D010455:Peptides; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D020866:omega-Conotoxin GVIA; D009568:Nitrendipine; D000242:Cyclic AMP; D008550:Melatonin; D002118:Calcium