alpha-Melanocyte stimulating hormone: immunohistochemical identification and mapping in neurons of rat brain.

alpha-Melanocyte stimulating hormone (alpha-melanotropin) immunofluorescence was observed in rat brain by means of a highly specific and well-characterized antibody. The hormone was contained in arcuate nucleus cell bodies and in varicose fibers. Dense populations of hormone-containing fibers were present in the septum, the nucleus interstitialis stria terminalis, and the medial preoptic, anterior hypothalamic, dorsomedial, and periventricular nuclei. Moderate numbers of fibers were seen in the paraventricular and arcuate nuclei, the amygdala, the region of the tractus diagonalis, the mammillary body, the central gray, the cuneiform nucleus, and the nucleus of the solitary tract. There is an interesting correlation of alpha-melanocyte stimulating hormone fibers with regions of noradrenergic axonal projections and terminal fields.