Catecholamine neurons in the squirrel monkey hypothalamus

Catecholamine neurons were found in the periventricular nucleus, arcuate nucleus, and a region around the mammillothalamic tract in the hypothalamus of the squirrel monkey. These neurons did not fluoresce in control or monoamine-oxidase-inhibited animals, and exhibited fluorescence only after intraventricular injections of alpha-methyl-norepinephrine. Dense accumulations of catecholamine varicosities appeared in the periventricular nucleus, external contact zone of the median eminence, and perivascular region of the median eminence; the arcuate nucleus contained no more than a moderate density of catecholamine varicosities. The median eminence fluorescence had a regional character, with greatest intensity in the caudal portion.