ABSTRACT

Alpha-melanocyte-stimulating hormone (MSH) was first described in neurons in the brain in 1978. The α-MSH immunoreactive material in the brain was later found to be comprised of both acetylated and desacetyl peptides, as occurs in the pituitary, but the brain contained relatively more of the desacetyl peptide. The findings have led to extensive studies of the pro-opiomelanocortin (POMC) neuronal system and multiple neurotransmitters in the central nervous system. Radioimmunoassay for α-MSH in microdissected areas of discrete regions of rat brain show the highest concentrations in the median eminence and the dorsomedial nucleus, followed by the arcuate and the periventricular nuclei of both the hypothalamus and thalamus. The pituitary was for some time considered the only biosynthetic site for POMC-related peptides. The POMC-related material found in the brain was thought to have been transported there and then absorbed. Sensitive antisera against a-MSH stain fibers in the hippocampus and cortex. Antisera against other POMC-related peptides do not stain fibers in these areas.