Effects of discrete medial preoptic hypothalamic lesions on the androgen gonadotropin feedback system in the male rat

Abstract

The effect of discrete lesions of the Anterior Medial Preoptic Area of the Hypothalamus (MPOA) in the control of pituitary gonadotropins in the adult male Wistar rat has been studied.Electrolytic lesions were made by passing an anodal current through tungsten electrodes.Electrodes were oriented stereotaxically into the MPOA and lesion placement was histologically checked.In sham controls, electrodes were lowered into the MPOA but no current was applied.Serum LH and FSH were measured by RIA.MPOA lesioned animals showed significantly lower plasma LH (p less than 0.01) in comparison to sham lesioned group.Plasma FSH remained unaltered.To test whether these results were related to an alteration in the negative feedback system, the response to administration of Testosterone Propionate (TP) and the secretion patterns of LH and FSH after castration were analyzed.Administration of TP revealed similar LH and FSH 24 and 48 h decrements and the pattern of LH and FSH secretion after gonadectomy was not significantly different in lesioned and sham lesioned animals.Responsiveness to exogenous LHRH was not impaired by MPOA lesions.The results suggest that neural elements within the MPOA are functionally related to pituitary LH secretion in the male rat.The LH control alteration in lesioned animals is not associated with modifications in negative feedback of androgens and pituitary sensitivity to LHRH remains unaltered.