Differential effects of ovarian local anaesthesia during pro-oestrus on ovulation by the right or left ovary in normal and hemi-ovariectomized adult rats.

Abstract

The effects on spontaneous ovulation in normal and hemi-ovariectomized cyclic rats of an injection of saline or a local anaesthetic (2-diethylamine-2',6'-acetoxilidide hydrochloride with adrenaline, Xylocaine; administered at 13:00 h) into the bursa ovarica, were studied to investigate the participation of ovarian innervation in the regulation of the response of ovarian follicles to endogenous gonadotrophins on the day of pro-oestrus. The injection of saline or Xylocaine into both ovaries did not affect ovulation by the right ovary. Bilateral injection of Xylocaine did not affect ovulation by the left ovary. However, when saline was injected into the right ovary and Xylocaine into the left ovary, the number of ova shed by the left ovary decreased significantly (0.9 +/- 0.7 versus 4.4 +/- 0.2, P < 0.01; Mann-Whitney U test). In hemi-ovariectomized animals, when the right ovary was anaesthetized, ovulation was similar to that in saline-treated animals, and when the right ovary was anaesthetized, ovulation was blocked (one of six animals ovulated). The injection of hCG at 14:00 h to hemi-ovariectomized rats did not restore ovulation, whereas all the rats ovulated when anaesthesia occurred at 18:00 h. The present results suggest that on the afternoon of the day of pro-oestrus, before the LH peak, a neural signal modulates the response of the left ovary to gonadotrophins.