Coexistence of immunoreactivity for melanin-concentrating hormone and alpha-melanocyte-stimulating hormone in the hypothalamus of the rat.

Coexistence of immunoreactivity for melanin-concentrating hormone (MCH) and alpha-melanocyte-stimulating hormone (alpha-MSH) within rat hypothalamic neurons has been examined by the unlabeled antibody enzyme method. Neurons exhibiting both MCH- and alpha-MSH-like immunoreactivities were found in the dorsolateral hypothalamus, whereas no MCH-like immunoreactive perikarya were seen in the arcuate nucleus, where some neurons were stained with alpha-MSH antiserum. There seem to be two distinct alpha-MSH-like immunoreactive neurons in the rat hypothalamus, one exhibiting coexistence with MCH-like immunoreactivity and the other not showing any cross-reaction with MCH antiserum.