Hypothalamic deafferentation inhibits the stimulatory influence of prolactin on follicle-stimulating hormone release in the golden hamster

We have examined the effects of PRL-producing ectopic pituitary grafts on plasma FSH and LH levels in male golden hamsters with anterior (AHD) and anteolateral hypothalamic deafferentation (ALHD). After hypothalamic deafferentation or sham deafferentation, hamsters received pituitary transplants under the kidney capsule. In the first experiment, the animals were unilaterally nephrectomized 5-6 weeks after transplantation to remove the ectopic pituitaries. In a second experiment the ectopic pituitaries remained under the kidney capsule for the duration of the experiment. Serial blood samples were collected before and after pituitary transplantation and after transplant removal. In the first experiment, ALHD resulted in a significant (P less than 0.01) suppression of plasma LH levels that lasted through the entire study, but had no significant effect on plasma FSH levels or on testicular and seminal vesicle weight. The presence of pituitary grafts resulted in a significant (P less than 0.01) elevation in plasma FSH levels in the sham-deafferented hamsters but had no effect on plasma FSH levels in those with ALHD. After transplant removal there was a significant (P less than 0.01) drop in plasma FSH levels in the hamsters that had been sham deafferented but not in those with a deafferented hypothalamus. Plasma LH levels were not affected by the pituitary transplants or their removal in either group. In the second experiment, ALHD but not AHD significantly (P less than 0.05) reduced testicular and seminal vesicle weights. Transplantation of an anterior pituitary elevated plasma FSH levels in the control group but not in the AHD and ALHD groups. Both types of deafferentations suppressed plasma LH levels below the limit of sensitivity of the assay for the duration of the experiment. Plasma PRL levels were markedly elevated only in the groups with an ectopic pituitary transplant. These results suggest that the anterior connections of the medial basal hypothalamus are necessary in order for PRL-producing pituitary transplants to influence FSH secretion from the in situ pituitary.