Pituitary Prolactin Secretion in Female Rats Made Persistently Estrous or Diestrous by Hypothalamic Deafferentation

Serum prolactin levels and pituitary prolactin concentration and total content were determined by radioimmunoassay in adult female rats which had been made constant-diestrous by complete deafferentation (CC) or constant- estrous by anterior deafferentation (AC) of the medial basal hypothalamus. Either cut severely altered prolactin secretion by blocking the “proestrous surge” of prolactin. In completely deafferented rats, serum prolactin levels were low but not significantly lower than cyclic diestrous levels. The pituitary weight in CC rats was markedly reduced and the pituitary prolactin concentration was as low as that seen late on the afternoon of proestrus or after long-term ovariectomy. In contrast, anterior-deafferented rats had serum prolactin levels almost as high as those observed late on the afternoon of proestrus. The pituitaries were enlarged in AC rats, the mean concentration of pituitary prolactin was similar to diestrous values, and the total pituitary content of prolactin was raised to a level similar to that encountered late on the afternoon of estrus. The changes in prolactin secretion in both CC and AC rats may be caused at least in part by alterations in estrogen secretion which in turn depend on changes in gonadotrophic secretion. (Endocrinology90: 862, 1972)