title: Progesterone in the ventromedial hypothalamus facilitates estrous behavior in ovariectomized, estrogen-primed rats.
abstract: The putative neural target sites of progesterone (P) action for the facilitation of estrous behavior in female rats were reexamined using the hormone implant technique. Subjects were ovariectomized, estrogen-primed Long-Evans females. All were outfitted with bilateral double barreled cannulae assemblies consisting of 23-gauge guide cannulae and 28-gauge inserts. Subjects in Exp 1 received sc injections of individually determined threshold priming doses of estradiol benzoate. Estrogenic priming for subjects in Exp 2 was provided by sc placed Silastic capsules (5 mm) filled with 17 beta-estradiol-cholesterol (1:20). Each subject was tested for estrous behavior with a male after P-filled cannulae and after blank inserts were lowered into the brain. Behavioral tests were conducted 1 and 4.5 h postcannulae placement. Thirty-five of 40 females with P in the ventromedial hypothalamus exhibited high levels of lordosis behavior during the 4.5-h test. Moreover, 29 of the 35 exhibited solicitation behavior as well. Estrous behavior was not exhibited by these animals during the 1-h test. Implants in other regions of the brain (i.e. mesencephalic reticular formation, preoptic area, central grey, caudate putamen, and hippocampus; n = 80) did not consistently facilitate estrous responsiveness. In Exp 3, levels of estrous responsiveness were similar before and after adrenalectomy (n = 10); thus, facilitation of estrous behavior by P-filled implants in the ventromedial hypothalamus was not dependent upon activation of the hypothalamic-pituitary-adrenal axis.
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D002369:Castration; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects*; D005260:Female; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D012826:Silicone Elastomers; D014697:Ventromedial Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*
chemical_list: D012826:Silicone Elastomers; D011374:Progesterone; D004958:Estradiol