PERIPHERAL SYMPATHETIC DENERVATION PROVOKED BY GUANETHIDINE INJECTIONRESULTS IN THE ADVANCEMENT OF OVULATION, INDUCED BY SEQUENTIAL GONADOTROPIN TREATMENT, IN PREPUBERTAL FEMALE GUINEA-PIGS

There is evidence that the sympathetic innervation of the ovary plays a role in regulating ovulation. We analysed the possibility that the o varian sympathetic innervation modulates the effects of gonadotrophins on ovulatory ability in the prepubertal guinea pig. Injection of guan ethidine sulfate into newborn female guinea pigs resulted in the advan cement of the age of vaginal opening, as compared with untouched contr ol animals (27 +/- 9 vs 37 +/- 0.9 days, p < 0.05). 24-48 h after the vaginal opening, neither untouched control nor guanethidine treated an imals showed signs of ovulation (presence of fresh corpora lutea in th e ovaries). The sequential injection of 10 IU of pregnant mare's serum gonadotrophin (PMSG), followed 56 h later by 10 IU of human chorionic gonadotrophin (hCG) into 10 day-old guinea pigs resulted in the advan cement of the age of vaginal opening (22 +/- 2.3 days vs 37 +/- 0.9 da ys, p < 0.05). When PMSG-hCG was administered to guanethidine-treated animals, the age of vaginal opening was significantly advanced as comp ared with PMSG-hCG-treated animals (17 +/- 0.8 vs 22 +/- 2.3 days,p < 0.05). Almost all animals treated with PMSG-hCG, denervated or not, ha d fresh corpora in their ovaries. Differences in the number of fresh c orpora lutea between denervated and non-denervated guinea pigs treated with PMSG-hCG were not observed. These results indicate that the sens itivity of the follicles to gonadotrophins is modulated in an inhibito ry way by noradrenergic innervation.