Progestin receptors in substance P-immunoreactive neurons in the hypothalamus of male guinea pigs after behaviorally effective estradiol pulse treatment.
Pulsatile administration of estradiol effectively primes orchidectomized (ORCH) male guinea pigs to display progesterone-facilitated lordosis. In contrast, a single injection of estradiol benzoate (EB) is not behaviorally effective. In ovariectomized female guinea pigs, estradiol pulses induce progestin receptors selectively in substance P neurons in the ventrolateral hypothalamus (VLH), a site at which estradiol primes females to respond behaviorally to progesterone. To test the hypothesis that behaviorally effective estradiol pulses induce progestin receptors selectively in substance P neurons in the VLH in males, ORCH animals received a single injection of EB 40 h before, or two pulses of estradiol-17 beta, 39 and 11 h before perfusion. Colchicine was administered intracerebroventricularly prior to perfusion. The only difference found between the two estradiol treatment groups was a higher number of progestin receptor-immunoreactive (PR-IR) cells in the rostral VLH of estradiol pulse-treated males. There were no significant differences in the number of PR-IR cells in the mid- or caudal VLH, nor in the number of substance P-immunoreactive (SP-IR) neurons in the VLH/ventromedial hypothalamus (VMH) of animals receiving the two estradiol treatments. Furthermore, the percentage of PR-IR cells in the VLH also immunoreactive for SP did not differ between the estradiol pulse- (22%-25%) and the EB-injected animals (22%-32%). These data do not support the hypothesis that administration of behaviorally effective estradiol pulses, as compared to behaviorally ineffective EB injections, induce progestin receptors selectively in substance P neurons in the VLH of male guinea pigs.
Olster
D H
DH
Department of Psychology, University of Massachusetts, Amherst 01003.
Blaustein
J D
JD
D000818:Animals; D003078:Colchicine / Q000494:pharmacology; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D006168:Guinea Pigs; D007276:Injections, Intraventricular; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009919:Orchiectomy; D011980:Receptors, Progesterone / Q000378:metabolism*; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D013373:Substance P / Q000276:immunology / Q000378:metabolism*; D014697:Ventromedial Hypothalamic Nucleus / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism*
D011980:Receptors, Progesterone; D013373:Substance P; D004958:Estradiol; D003078:Colchicine