Effect of naloxone and beta-casomorphin on the hypothalamic-pituitary-luteinizing hormone axis in vitro.
The effect of naloxone and beta-casomorphin on luteinizing hormone (LH) release from pituitary cell aggregates, obtained by three-dimensional culture, with or without mediobasal hypothalamic fragments was studied in vitro. Short-term naloxone perifusion at a concentration of 10(-5)M did not modify either basal or LHRH-stimulated LH release from the pituitary cell aggregates. In contrast, a 12-min naloxone perifusion at the same concentration caused an increase in LH release in the mediobasal hypothalamic-pituitary cell aggregate axis. This increase was rapid (12-16 min after time pulse), marked [up to 10 times (p less than 0.004) the initial base line], short (return to the base line secretion 32-40 min after the beginning of the time pulse) and dose-dependent, with a rise greater than 1000% at a concentration of 10(-4) (p less than 0.006). The same effect was observed when a second pulse was applied 48 min after the first one. LH release induced by naloxone was antagonized 56 +/- 2% (p less than 0.03) by beta-casomorphin (an exogenous opiate) at a concentration of 10(-5) M. beta-casomorphin alone did not modify LH basal secretion, but inhibited 25.1 +/- 2.4% (p less than 0.008) LH release enhanced by LHRH. These results indicate that naloxone, an opiate antagonist, markedly increases LH release via a mu-type opioid receptor mechanism at the hypothalamic level only, during short-term exposure.
Shacoori
V
V
Laboratoire de Physiologie Pharmaceutique, Faculté de Pharmacie, Rennes, France.
Guerin
J
J
Girre
A
A
Saïag
B
B
Rault
B
B
D000818:Animals; D002364:Caseins; D002478:Cells, Cultured; D004723:Endorphins / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D007033:Hypothalamus, Middle / Q000187:drug effects; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010477:Perfusion; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013223:Statistics as Topic
D002364:Caseins; D004723:Endorphins; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; C021968:beta-casomorphins; D007986:Luteinizing Hormone