Melatonin-and serotonin-stimulated release of vasopressin from rat neurohypophysis in vitro.
In order to study the control of vasopressin-release, the effect of a series of potential agents was studied in an in vitro perifusion system of rat neurohypophysis after in vivo treatment with nialamide, a monoamine oxidase inhibitor. In this system, metlatonin stimulated vasopressin-release in a dose-dependent manner (1 x 10-8 to 1 x 10-3 M). Serotonin (1 x 10-3 M) also led to a significant increase of vasopressin-release whereas quipazine (1 x 10-3 M), a putative serotonin agonist and monoamine oxidase inhibitor, caused a 3-fold stimulation of the release of the neurohormone. The stimulatory effects of melatonin and serotonin were prevented by omission of Ca2+ combined to an excess of Mg2+ (12mM) in the perifusion medium. 1 x 10-6 M somatostatin did not affect basal or melatonin-stimulated vasopressin-release. These results show that melatonin and serotonin can have a direct stimulatory effect on vasopressin release at the neurohypophyseal level.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009526:Nialamide / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D014667:Vasopressins / Q000378:metabolism*
D014667:Vasopressins; D012701:Serotonin; D008274:Magnesium; D008550:Melatonin; D002118:Calcium; D009526:Nialamide