Development of estradiol-induced progestin receptor immunoreactivity in the hypothalamus of female guinea pigs.
The inability of young female guinea pigs to display progesterone-facilitated lordosis has been attributed, in part, to a deficiency in the concentration of hypothalamic estradiol-induced progestin receptors, as measured by in vitro binding assays. An immunocytochemical technique was used to ascertain where, within the mediobasal hypothalamus, estradiol-induced progestin receptor levels are lower in immature than in adult females. Adult (greater than 7 weeks) and juvenile (3 weeks) ovariectomized females received 10 micrograms estradiol benzoate, a dose that primes adult, but not immature females to respond behaviorally to progesterone. Progestin receptor-immunoreactive (PR-IR) cells were counted in the arcuate nucleus (ARC) and ventrolateral hypothalamus (VLH), the two regions containing the densest populations of estradiol-induced progestin receptors in the mediobasal hypothalamus. There was no age difference in the number of PR-IR cells in the rostral or caudal VLH, but immunostaining was darker in the rostral VLH of juveniles as compared to adults. We found similar numbers of PR-IR cells in the rostral and mid-ARC, but 35% fewer immunostained cells in the caudal ARC of immature, as compared to adult females. Furthermore, staining intensity was weaker in the mid- and caudal ARC of the juvenile females. These data suggest that the ARC, not the VLH, is a site of fewer estradiol-induced progestin receptors in immature females.
Olster
D H
DH
Psychology Department, University of Massachusetts, Amherst 01003.
Blaustein
J D
JD
D000375:Aging / Q000378:metabolism; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000033:anatomy & histology / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D007031:Hypothalamus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000033:anatomy & histology / Q000187:drug effects; D007150:Immunohistochemistry; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology; D011980:Receptors, Progesterone / Q000187:drug effects* / Q000276:immunology
D011980:Receptors, Progesterone; D011374:Progesterone; D004958:Estradiol