PERIPHERAL SYMPATHETIC DENERVATION INDUCED BY GUANETHIDINE IN NEWBORNRATS RESULTS IN THE ADVANCEMENT OF OVULATION BUT DOES NOT MODIFY ESTROGEN POSITIVE FEEDBACK EFFECTS

There is evidence that ovarian sympathetic innervation plays a stimula tory role in the regulation of spontaneous puberty and ovulation. We h ave investigated the possibility that it modulates the effects of gona dotrophins or oestrogens on ovulation ability, in infantile rats. The injection of 10 mu g of oestradiol benzoate (OB),8 i.u. of pregnant ma re's serum gonadotrophin (PMSG) or 8 i.u. of PMSG followed 56 h later by 10 i.u. of human chorionic gonadotrophin (hCG) to 15-old unoperated or denervated rats (peripheral sympathetic denervation induced by the administration of guanethidine monosulfate to newborn female rats) di d not advance ovulation. The injection of OB to 18- or 21-days old rat s, denervated or not, did not induce ovulation. When 18- or 21-days ol d rats received PMSG, four out of 16 ovulated, while the same treatmen t given to guanethidine-treated animals increased ovulation (10 out of 18 rats ovulated). There were no differences in the number of ova she d by unoperated and denervated rats. When 21-day old unoperated rats w ere injected with PMSG-hCG, ova were recovered only in two out of eigh t treated rats (10 and 16 ova respectively). When sympathetic-denervat ed rats received the same treatment all eight rats ovulated, and relea sed 22.0 +/- 2.3 ova. These results suggest that the sympathetic inner vation of the ovary or the median eminence do not play a role in the p ositive feedback effects of oestrogen resulting in a first ovulation d uring the infantile period. On the other hand, at the end of the infan tile period the sympathetic innervation of the ovary plays an inhibito ry role in the response of the ovaries to gonadotrophins. (C) 1998 Lip pincott-Raven Publishers.