Gonadotropin releasing hormone release from the rat hypothalamus: dependence on membrane depolarization and calcium influx.
Release of gonadotropin-releasing hormone (GnRH) was studied by incubating individual rat hypothalami for 60 min, after a 30-min preincubation period, and measuring GnRH in the medium by immunoassay. During the 1 h of incubation, endogenous GnRH release was linear and exogenous GnRH was not destroyed. Membrane depolarization produced by increasing the medium potassium concentration to 60 mM increased GnRH release to 200-500% of control. Membrane depolarization produced by adding 10(-5) or 10(-4) M ouabain increased GnRH release to 200% of control. Melatonin (10(-7) M) and prostaglandin E2 (4 X 10(-4) M) Aslo stimulated GnRH release to 200% and 170% of control, respectively. Inhibition of calcium influx by omission of medium calcium and addition of 0.05 M EDTA reduced GnRH release to 50% of control. Both no calcium-EDTA medium and verapamil (10(-5) M) prevented the stimulation of GnRH release by 60 mM potassium, 10(-3) M melatonin, and 4 X 10(-4) M prostaglandin E2. We conclude that hypothalamic GnRH release depends on membrane depolarization and calcium influx, as does the secretion of hormones from other endocrine tissues.
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D004492:Edetic Acid / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats
D007987:Gonadotropin-Releasing Hormone; D010042:Ouabain; D004492:Edetic Acid; D011188:Potassium; D002118:Calcium