Long-term oestrogen priming on basal and oestradiol-induced release of luteinising hormone secretion in male rats.
The response of prolonged oestrogen priming (by silastic implants) of the male rat hypothalamic-pituitary axis (HPA) to an oestrogen challenge test was investigated. Basal LH levels were suppressed to a maximum at two months and remained unchanged by four months. In contrast to response in human, oestrogen priming had failed to stimulate a positive feedback response to an oestrogen challenge test in the male rats. Instead, oestrogen priming might have attenuated the negative LH feedback response. Increasing the dose of oestrogen priming by increasing the duration was not effective in inducing positive feedback in the male rats. The failure of these priming regimes to stimulate positive feedback in male rats may reaffirm our earlier suggestion that oestrogen does not play an important role in activating the cyclic centre in rats. This would also contradict the suggestion that testicular secretions may have acted through conversion to oestradiol in the suppression of the cyclic system in males during the critical period of differentiation of the HPA.
Loke
D F
DF
Department of Obstetrics and Gynaecology, National University of Singapore, National University Hospital.
Ratnam
S S
SS
Goh
H H
HH
D000818:Animals; D004343:Drug Implants; D004958:Estradiol / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology*; D004966:Estrogens, Conjugated (USP) / Q000494:pharmacology*; D005246:Feedback; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D007273:Injections, Intramuscular; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D004343:Drug Implants; D004966:Estrogens, Conjugated (USP); D004958:Estradiol; D007986:Luteinizing Hormone