Immunofluorescence study of LRF neurons in primates.

LRF producing neurons were characterized in the squirrel-monkey (Saimiri sciurus) and Cebus apella monkey, by means of a rabbit antiserum against unconjugated synthetic LRF, previously adsorbed on polyvinylpyrrolidone. These neurons, which vary in number according to the species and physiological or experimental conditions, are mainly concentrated in the mediobasal hypothalamic area (infundibular and premammillary nuclei in particular) and the vascular organ of the lamina terminalis. The neurons of the first group give rise to axons which terminate round the capillaries of the primary portal plexus of the infundibulum. Those of the second group give rise to axons which terminate round the capillaries of the primary and secondary plexuses of the vascular organ of the lamina terminalis and in the ependyma which lines its ventricular side. Some specifically immunoreactive axons apparently run towards the telencephalon (passing in front of and behind the anterior white commissure), the mescencephalon and the epithalamus. Some of the latter give rise to terminal ramifications in the area of the median habenular nucleus.