Reproductive behavioral responsiveness to noradrenergic stimulation in developing guinea pigs.
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.
Olster
D H
DH
Psychology Department, University of California, Santa Barbara 93106, USA. olster@psych.ucsb.edu
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*
D000316:Adrenergic alpha-Agonists; D004958:Estradiol; D003000:Clonidine; D009638:Norepinephrine