1980 Volume 56 Issue 7 Pages 885-894
LH-RH synthesizing neurons in the hypothalamus of the Japanese monkey (Macaca fuscata) were revealed by immunohistochemistry.
Their cell somata, neuronal processes and terminals showed a dark brown colored reaction by the peroxidase-antiperoxidase (PAP) method. Their cell somata which synthesize LH-RH were classified into four groups. The neurons of the first group were located mainly in the preoptic area and the anterior wall of the third ventricle and also extended to the nucleus of the diagonal bundle of Broca and the medial septal nucleus. Those of the second group were distributed in the dorsomedial and the ventromedial hypothalamic nuclei and in the area round the suprachiasmatic nucleus. Those of the third group were found in the area from the arcuate nucleus to the infundibular stalk. Those of the fourth group located in the area round the mammillary body. The nerve projection from all of the neurons in these four groups was observed in the median eminence (ME). Furthermore, the pathways to the ME were also classified into four groups by way of the projection. The first group of fibers originated from the whole cell groups of the first group, and the neurons round the suprachiasmatic nucleus of the second group ran through the medial part of the floor of the third ventricle and terminated in the ME. The second group of fibers from the neurons in the first group diverged laterally in the dorsal part of the optic chiasma and projected to the ME. The third group of fibers from the neurons in the dorsomedial and ventromedial nuclei of the third group a along the third ventricle and terminated in the ME. The fourth group of fibers from the neurons in the mammillary body ran rostrally in the bottom of the brain and projected in the ME.
Besides the LH-RH neuronal processes projecting to the ME, the neuronal pathways to the extrahypothalamic areas were also confirmed in this investigation. One of those fibers ran toward the septal nucleus through the dorsal part of the anterior commissure. The other ran caudally through the dorsal part of the dorsomedial hypothalamic nucleus toward the thalamus. Fibers toward the rostral part of the diagonal bundle of Broca were also detected. However, it was very hard to trace those extrahypothalamic LH-RH fibers to the terminal portions. The relatively small numbers of the terminals of LH-RH neurons were also found in the organum vasculosum laminae terminalis (OVLT).
