title: Reproductive behavioral responsiveness to noradrenergic stimulation in developing guinea pigs.
abstract: The stimulatory effects of ovarian hormones on sexual receptivity in guinea pigs may be mediated by norepinephrine. Juvenile females rarely exhibit steroid-induced receptivity and also respond poorly to the lordosis-enhancing action of alpha-noradrenergic receptor stimulation. This experiment was designed to chart the development of behavioral responsiveness to the alpha-noradrenergic agonist, clonidine, and to test the hypothesis that higher doses of estradiol and/or clonidine are required to stimulate lordosis in juvenile compared to adult guinea pigs. Ovariectomized females received estradiol benzoate (10 microg or 50 microg SC) 40-48 h before administration of clonidine (1 mg/kg or 5 mg/ kg IP) or saline at 14-17-day intervals. Regardless of treatment, few animals (0-36%) displayed lordosis at 20, 34, or 48 days of age. At 65 days of age, in both estradiol dose groups significantly more clonidine- (1 mg/kg) than saline-injected animals displayed lordosis (80-91 vs. 0-33%, respectively). Clonidine (5 mg/kg) was ineffective at all ages. These data do not support the hypothesis that behavioral responsiveness to alpha-noradrenergic receptor stimulation in immature females can be elicited by increasing the doses of estradiol and/or clonidine. These results suggest the occurrence of a maturational change in the neural systems governing noradrenergic involvement in steroid-induced sexual behavior in guinea pigs.
authors.affiliation: Psychology Department, University of California, Santa Barbara 93106, USA. olster@psych.ucsb.edu
authors.forename: D H
authors.initials: DH
authors.lastname: Olster
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000375:Aging / Q000502:physiology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D009638:Norepinephrine / Q000494:pharmacology*; D010052:Ovariectomy; D011187:Posture / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
chemical_list: D000316:Adrenergic alpha-Agonists; D004958:Estradiol; D003000:Clonidine; D009638:Norepinephrine