Differences in spontaneous ovulation in rats with unilateral lesion of the hypothalamus

The effects of unilateral lesion of the anterior (AH), median (MH) or posterior hypothalamus (PH) performed on diestrus 1, on ovulation and estrous cycle were analyzed in virgin rats. Only rats showing two consecutive estrous cycles of the same length were used. The lesion of AH decreased the ovulation rate (number of ovulating/number of treated rats) (14/26 vs. 24/24 of sham-operated group, p less than 0.01, Chi-square test), and the number of released ova per rat (5.0 +/- 1.1 vs. 10.3 +/- 0.8, p less than 0.05). Meanwhile, for ovulating animals no differences in the number of ova shed were observed. Lesions of the MH or PH did not modify the ovulation rate nor the number of ova shed. The left ovary of rats with MH and PH lesions, however, shed less ova than the left ovary of the control group (MH: 4.1 +/- 0.5; PH: 3.9 +/- 0.6; control: 5.7 +/- 0.5, p less than 0.05). These results suggest that neural information arising from the AH, MH or PH plays different roles in the regulation of ovulation.