GnRH receptors in rat brain, pituitary and testis; modulation following surgical and gonadotropin-releasing hormone agonist-induced castration.
The regulation of rat gonadotropin-releasing hormone (GnRH) receptors in male rat pituitary, hippocampus and testis was studied, in vivo, under steady-state conditions during treatment with D-Trp6 GnRH (triptorelin, slow-release form, at 300 micrograms/kg/month). GnRH receptors were characterized on tissue sections by quantitative autoradiography using 125I-GnRHa as a tracer. Castrating doses of triptorelin strongly down-regulated pituitary GnRH receptors (50% of reduction after 8 h, 80% on days 1-30); in contrast, only a transient decrease (20% at 8 h) was observed in the hippocampus with a rapid return to control levels. Triptorelin induced a marked (2-fold) increase in GnRH receptors in testicular interstitial tissue during 5 days with a return to control value by day 20. Administration of a GnRH antagonist (BIM 21009, 1 mg/kg/24 h) induced a rapid reduction of pituitary and testicular receptors to undetectable levels at 24 h, while hippocampal receptors were strongly reduced only. This indicates that GnRH receptors with similar pharmacology are differently controlled in various tissues and that brain receptors are likely to be also regulated by GnRH agonists and antagonists.
Ban
E
E
Pharmacologie Neuro-Immuno-Endocrinienne, CNRS UA 1113, Institut Pasteur, Paris, France.
Crumeyrolle-Arias
M
M
Latouche
J
J
Leblanc
P
P
Heurtier
J F
JF
Drieu
K
K
Fillion
G
G
Haour
F
F
D000818:Animals; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D010906:Pituitary Hormone-Releasing Hormones / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D011966:Receptors, LHRH / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D017329:Triptorelin Pamoate
D010906:Pituitary Hormone-Releasing Hormones; D011966:Receptors, LHRH; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; C053242:LHRH propylamide, Ala(6)-des-Gly(10)-