Differences in the distributional pattern of CRF-, oxytocin-, and vasopressin-immunoreactive nerve fibers in the median eminence of the rat.

Conspicuous differences in the distributional pattern of nerve fibers containing corticotropin-releasing factor (CRF) or posterior lobe hormones, respectively, were shown in the median eminence of the adult male rat by means of immunoperoxidase histochemistry, with the use of anti-CRF, anti-oxytocin, and anti-vasopressin sera. In the rostral and central divisions of the median eminence, a high concentration of CRF-immunoreactive nerve fibers was found in the median portion of the external layer; these fibers terminated on the capillary loops of the hypophysial portal system. In the caudal division of the median eminence, the CRF-immunoreactive nerve fibers were located in the median to paramedian portions of the external layer. Numerous oxytocin- and vasopressin-immunoreactive nerve fibers were observed evenly distributed throughout the internal layer of the median eminence. In the external layer, a small number of the oxytocin- and vasopressin-containing nerve fibers was found around the capillary loops, particularly in the median to paramedian portions. The distributional patterns of the CRF and the posterior lobe hormones in the hypothalamo-hypophysial system and their functional interrelationship are discussed.