Immunocytochemical localization of luteinizing hormone-releasing hormone in neurons in the medial basal hypothalamus of the female rat.

Luteinizing hormone-releasing hormone (LHRH)-neurons were localized with a LHRH antiserum (WP-1) in the medial basal hypothalamus (MBH) of the female rat using the sagittal hypothalamic slice preparation in combination with the peroxidase-antiperoxidase immunocytochemical technique of Sternberger (1979). Numerous darkly-stained perikarya were visualized in the cell-poor zone, lateral arcuate nucleus and the median eminence. The processes of these neurons contributed to the intensely-stained fiber bundle above the tuberoinfundibular sulcus. The fibers in this tract run in a rostrocaudal plane in the lateral external zone of the median eminence. Also, numerous fibers course into the internal zone of the median eminence, perpendicular to the rostrocaudal plane. Several LHRH-immunoreactive perikarya also were identified in the periventricular area caudal to the optic chiasm (retrochiasmatic area). The LHRH neurons were small (10 micron) bipolar neurons with fibers (dendrites) exiting from either pole which showed very little branching. It appears that the sagittal slice in combination with the appropriate fixation procedure and LHRH antiserum enabled us to demonstrate the presence of LHRH-immunoreactive perikarya in the MBH of the female rat.