Pituitary gland responsiveness to LHRH and LHRH neuronal responsiveness to excitatory stimuli are severely impaired in female rats treated neonatally with high doses of androgen.
Treatment of neonatal female rats with androgen renders these animals permanently sterile as adults. Previously, we reported that these androgen-sterilized rats (ASR) do not respond to the positive feedback effects of estrogen by having LH surges. We also reported that this defect might be due to the failure of these animals to show increased hypothalamic norepinephrine turnovers (an index of secretion) in response to steroid treatment. Although LHRH-catecholamine synapses are established before or at birth, whether such synapses are functional remains to be resolved. Accordingly, in the present studies, female rats were given 1.25 mg of testosterone propionate at 5 days of age and, at 100 days of age, these ASR and controls were ovariectomized and treated with estradiol. In these animals, we examined whether activation of medullary A1 noradrenergic neurons would amplify LH release following preliminary depolarization of LHRH neurons with an electrochemical stimulus (ECS). As well, we reexamined whether LHRH neuronal responsiveness to exogenous NE and pituitary responsiveness to LHRH differ in controls versus ASR. In controls, two pulses of LHRH given 60 min apart elicited increases in plasma LH with the second pulse inducing greater LH release than the first pulse. In ASR, significantly less LH was released after either LHRH pulse and particularly after the second pulse. When the spacing between the two LHRH pulses was reduced to 25 min, equivalent levels of LH release occurred in controls and ASR after the second pulse.(ABSTRACT TRUNCATED AT 250 WORDS)
Liaw
J J
JJ
Center for Studies in Reproduction, School of Medicine, University of Maryland, Baltimore 21201.
Barraclough
C A
CA
D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007276:Injections, Intraventricular; D007986:Luteinizing Hormone / Q000097:blood; D009474:Neurons / Q000187:drug effects*; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects*; D011247:Pregnancy; D011301:Preoptic Area / Q000502:physiology; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley
D000728:Androgens; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D009638:Norepinephrine