Distribution of immunoreactive substance P neurons in the hypothalamus and pituitary of the rhesus monkey

The distribution of immunoreactive substance P (IR‐SP) neurons was examined in the hypothalamus and pituitary gland of the rhesus monkey by using the peroxidase‐antiperoxidase immunocytochemical technique. Immunoreactive SP cell bodies were observed in the arcuate nucleus, in the region lateral to the arcuate nucleus, and in the median eminence (ME). Immunoreactive SP cells were also seen in the periventricular area of the dorsal tuberal region. A rich network of SP fibers was concentrated in the arcuate region, and the fiber stain was particularly dense in the external zone of the median eminence and in the external layer of the infundibular stalk. Also, substance P fibers were seen in the internal layer of the pituitary stalk and in the neural lobe of the pituitary gland. Outside the hypothalamus a dense network of IR‐SP fibers was observed in the globus pallidus.