Secretion of Pituitary Luteinizing Hormone and Follicle Stimulating Hormone in Female Rats Made Persistently Estrous or Diestrous by Hypothalamic Deafferentation

Serum LH and FSH levels and pituitary LH concentration and total content were determined by radioimmunoassay in cycling adult female rats and rats which had been made persistent- estrous by extended anterior deafferentation (AC) or constant-diestrous by complete deafferentation (CC) of the medial basal hypothalamus. Both types of cut drastically altered LH and FSH secretion from their cyclic patterns by blocking the “proestrous surge” of these two hormones. Serum LH titers were somewhat elevated in anterior- deafferented rats, values ranging between levels seen on the afternoons of diestrus and proestrus; FSH values were similar to those seen on the afternoon of estrus. The pituitaries were enlarged in AC rats but the mean concentration of pituitary LH was lower than that of cycling rats with the result that the total pituitary LH content was similar to levels seen on the afternoon of proestrus. In completely-deafferented rats, serum LH was very low but FSH values were only slightly depressed when compared with cycling animals. The pituitary weight in CC rats was markedly reduced and the pituitary LH concentration and total content were reduced as well. The results suggest that neurons entering the basal hypothalamus from its rostral or anterior end and those entering from other parts of its perimeter, e.g., laterally, influence gonadotrophic secretion by different mechanisms. (Endocrinology90: 855, 1972)