Hypothalamic control of ovulation and behavioral estrus in the cat

The estrous cat ordinarily ovulates only after a complex mating behavior pattern which involves an elaborate after reaction. The present experiments were designed to determine whether identical or separate hypothalamic areas control mating behavior and the release of an ovulatory surge of pituitary gonadotropin. With stereotaxic methods under chloralose anesthesia the hypothalami of naturally estrous or estrogen-gonadotropin-primed queens were stimulated bilaterally in one of the following regions: medial basal hypothalamus including the premamillary area (MBH) and the anterior hypothalamus including both medial and lateral divisions (AH, MAH, LAH). At the end of the stimulation period (5 V, 30 c/s, 5 ms duration, 30 s off for 30 min) bilateral anodal electrolytic lesions were made at the stimulation sites (3 mA for 30 s) with the central tips of the bipolar electrodes. Characteristically, ovulation was induced by stimulating the MBH but not the AH. Furthermore, the MBH lesions usually caused ovarian atrophy which led to anestrus, but the cats mated normally if supplied with exogenous estrogen. The anterior lesions left the ovaries in good trophic condition, and they could be ovulated by stimulating the MBH. However, the cats with anterior hypothalamic lesions in either the medial or lateral position repeatedly refused to accept the male even when primed with exogenous estrogen. The results from these combined stimulation and lesion experiments in the female cat indicate that a hypothalamic sex behavioral area lies rostral to and discrete from a tubero-mamillary area controlling the release of pituitary gonadotropin.