Differential response of luteinizing hormone-releasing hormone in the basal hypothalamus and the preoptic area following anterior hypothalamic deafferentation and/or castration in male rats.

Serum LH, FSH and LHRH concentrations and the LHRH content in the medial basal hypothalamus (MBH) and the preoptic area (POA) were measured by radioimmunoassay in male rats 33 days after anterior hypothalamic deafferentation (AHD) and/or castration. In castrate rats following AHD, there was a significant decrease in serum LH, FSH, and LHRH concentrations, whereas, in intact rats, serum LH was elevated in AHD over the sham AHD rats. Castration and AHD each caused a significant fall in the LHRH levels in the MBH; the decline was more pronounced in rats undergoing both castration and AHD. In contrast, deafferentation in intact and castrate rats resulted in the accumulation of LHRH activity in the POA. These studies support the suggestion that a) a substantial amount of LHRH normally found in the MBH of intact and castrate male rats originates in the rostral regions and, b) the LHRH-containing neural elements within the MBH have the competence to respond to a loss in the circulating testicular steroids.