Morphological and cytochemical study of a hypothalamochiasmatic perivascular neuronal system.

The topographical localization and some cytochemical characteristics of groups of perivascular neurons in the hypothalamus and in the optic chiasma have been studied. In the anterior hypothalamic area there are neuronal groups located around the blood vessels which penetrate the optic chiasma still associated with neurons. These perivascular neurons show some characteristics similar to those observed in neurosecretory hypothalamic neurons, but differ from them in that they show a greater intensity of thiaminopyrophosphatase and nucleoside-diphosphataseactivities. It is suggested that these neuronal groups may constitute a special hypothalamochiasmatic-perviscular-neurosecretory system (H. Ch. P. N. S.).