title: Estradiol pulses induce progestin receptors selectively in substance P-immunoreactive neurons in the ventrolateral hypothalamus of female guinea pigs.
abstract: Low doses of estradiol, administered as pulses, are as effective as higher doses for priming ovariectomized (OVX) guinea pigs to display progesterone-facilitated lordosis. High doses of estradiol, administered by constant-release implants, induce progestin receptors in many substance P-immunoreactive (SP-IR) neurons in the ventrolateral hypothalamus (VLH), a site at which estradiol primes OVX guinea pigs to respond behaviorally to progesterone. To test the hypothesis that behaviorally effective estradiol pulses induce progestin receptors selectively in substance P-containing neurons in the VLH, OVX females received estradiol implants 1 week prior to perfusion, or two pulses of estradiol-17 beta, injected 39 and 11 h before perfusion. Colchicine was administered intracerebroventricularly prior to perfusion. No significant differences were observed in the total number of progestin receptor-immunoreactive (PR-IR) or substance P-immunoreactive cells in the VLH and VLH/ventromedial hypothalamus (VMH), respectively, of females receiving the two estradiol treatments. However, the percentage of PR-IR cells in the VLH also immunoreactive for SP was significantly higher in the estradiol pulse-treated (53%), than in the estradiol capsule-implanted animals (36%). These data suggest that behaviorally effective estradiol pulses induce progestin receptors selectively in substance P-containing neurons in the VLH and are consistent with the hypothesis that substance P is involved in progesterone-facilitated lordosis in guinea pigs.
authors.affiliation: Department of Psychology, University of Massachusetts, Amherst 01003.
authors.forename: D H
authors.initials: DH
authors.lastname: Olster
authors.forename: J D
authors.initials: JD
authors.lastname: Blaustein
mesh_terms: D000818:Animals; D003078:Colchicine / Q000494:pharmacology; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010052:Ovariectomy; D010477:Perfusion; D011980:Receptors, Progesterone / Q000187:drug effects* / Q000276:immunology; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D013373:Substance P / Q000276:immunology / Q000378:metabolism*; D014697:Ventromedial Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*
chemical_list: D004343:Drug Implants; D011980:Receptors, Progesterone; D013373:Substance P; D004958:Estradiol; D003078:Colchicine