Morphological organization of catecholamine terminals in the diencephalon of the rhesus monkey.

The hypothalamus and thalamus of the rhesus monkey were investigated using the fluorescence histochemical method of Falck and Hillarp. The hypothalamus was found to be richly supplied with catecholamine fluorescent nerve terminals with many thick and a few varicosities, whereas nerve terminals with fine varicosities were found to be distributed over the thalamus except for the midline and medial nuclei which were innervated by nerve terminals with thicker and more intense fluorescent varicosities. The morphological characteristics and distribution pattern of catecholamine terminals were similar between the rhesus monkey and the rat. However, some species differences were noted in the suprachiasmatic nucleus, arcuate nucleus and internal layer of infundibulum in the hypothalamus. The pulvinar, which was nonexistent in the rat, had fine terminals.