THE EFFECT OF HYPOTHALAMIC LESIONS ON OVARIAN FUNCTION IN THE EWE1

Abstract

In 20 regularly cycling ewes, stereotaxic lesions were placed in various parts of the hypothalamus, and changes in estrous behavior, ovarian cycles, pituitary gonadotrophin content as well as adrenal and thyroid function were studied. Destruction of the pituitary stalk and adjacent ventral hypothalamus was associated with absence of both ovarian and behavioral cycles (4 animals). Destruction of an area immediately above the anterior median eminence inhibited estrous behavior without affecting ovarian cycles (3 animals). Extensive lesions in other parts of the hypothalamus (13 animals) had no effect on these parameters. In two animals with stalk lesions peripheral 17-hydroxycorticoid levels were not elevated following stress but in none of the animals was there significant adrenal or anterior pituitary atrophy. The FSH content of the anterior pituitary was somewhat depressed without a definite change in the LH content in animals with stalk lesions. Animals with lesions which did not involve the stalk had normal pituitary gonadotrophin content. Normal sheep which have entered the anestrous phase of their yearly cycle had a lower pituitary LH content than ewes during the polyestrous part of the year.