Hypothalamic unit activity in the cat: effects of estrogen and vaginal stimulation.

Abstract

Unit activity of single neurons in the anterior and posterior hypothalamic areas was studied in response to cervical stimulation in the adult female cat under the following conditions: anestrus ovariectomized and estrogen-treated ovariectomized. 35 mature female cats were used. Tungsten microelectrodes measuring .5 to 1.5 mcm at the tips were used for recording extracellular unit activity from the anterior and posterior hypothalamic nuclei. The stereotaxic coordinates used were based on Snider and Niemers Stereotaxic Atlas of the Cat Brain. After passing through a high impedance cathode follower the responses were amplified with a preamplifier and displayed on a dual-beam oscilloscope simultaneously stored on magnetic tape. Stimulation of the vaginal cervix consisted of short repeated movements of a lubricated Teflon probe. The results showed that cells in the anterior and posterior hypothalamus were influenced by stimulation of the vaginal cervix. There was a greater tendency for increased firing rates in the anterior as compared to the posterior hypothalamus. Estrogen treatment did not change the responsiveness of cells in the anterior hypothalamus but was associated with a general depression of unit activity in the posterior hypothalamus. The units which responded to vaginal cervix stimulation were not influenced by non-sexual stimulation (e.g. pinching the tail) used as a control. The findings suggest that the posterior hypothalamus may play a role in the regulation of ovulation and expression of sexual behavior in the cat.