Diurnal variation in norepinephrine-stimulated release of pineal serotonin in vitro.
Adult, male rats were maintained under 12L:12D with lights on at 06.00h. Their pineal glands were incubated at 37 degrees C in the presence or absence of 10(-4)M norepinephrine (NE). 5-HT and various metabolites were quantitated in post-incubation media and pineal glands by high performance liquid chromatography coupled with electrochemical detection. No differences were observed in the quantities of 5-HT released by pineal glands in four hour incubations starting at either 06.00, 13.00 or 18.00 h; however, a highly significant decrease below these levels was observed at 01.00h. NE significantly stimulated 5-HT release at 13.00 and 18.00 h, but was ineffective at 01.00 and 06.00h. These results confirm recently reported stimulatory effects of NE on the release of 5-HT into pineal gland incubation medium and further suggest a diurnal rhythm of pineal gland sensitivity to NE in vitro with maximum stimulation of 5-HT release at midphotophase.
Department of Anatomy, University of Arizona, Tucson.
B
B
Benson
W D
WD
Reynolds
D M
DM
Burns
C A
CA
Leadem
D000818:Animals; D002940:Circadian Rhythm; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010870:Pineal Gland / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000494:pharmacology
D012701:Serotonin; D014364:Tryptophan; D009638:Norepinephrine