Modulation of luteinizing hormone(LH) release by clonidine and opioid peptides in castrated male rats.
The effect of clonidine, a central alpha-adrenergic agonist, on the suppression of LH release induced by beta-endorphin or FK33-824, an endogenous opioid peptide or its synthetic analog, was investigated in castrated male rats, with or without pretreatment with reserpine. Pulsatile LH secretion was inhibited by intravenous injection of FK33-824 (400 micrograms/kg), or intraventricular injection of beta-endorphin (5 micrograms). Without pretreatment with reserpine, intraperitoneal administration of clonidine (1 mg/kg) failed to reverse the inhibition of LH release induced by these peptides. However, with pretreatment with reserpine (10 mg/kg), clonidine abolished the inhibitory effect on LH secretion induced by these peptides in castrated male rats. These data indicate that, unlike the results in ovariectomized, steroid-primed rats, pretreatment with reserpine allows the alpha-adrenergic system to act more peripherally than the opioid neuronal system in a neuronal network-regulating LH release in castrated male rats.
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D004347:Drug Interactions; D004723:Endorphins / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
D004723:Endorphins; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D007986:Luteinizing Hormone; D003000:Clonidine