Localization of α-Melanocyte-Stimulating Hormone in Rat Brain and Pituitary

Abstract
The distribution of .alpha.-melanocyte-stimulating hormone (.alpha.-MSH) was studied in the rat brain with an immunoperoxidase technique. .alpha.-MSH-containing cells were found in the arcuate nucleus of the hypothalamus. Cells staining for .alpha.-MSH were also localized in the intermediate lobe of the pituitary. .alpha.-MSH-containing nerve fibers extended throughout regions of the hypothalamus, thalamus and midbrain. Two weeks after hypophysectomy, .alpha.-MSH-positive cells and fibers were still present in the brain. .alpha.-MSH of non-pituitary origin is synthesized and stored by neural structures in the rat brain. The detection of .alpha.-MSH by radioimmunoassay in the rat brain and pituitary supports these observations.