The distribution pattern of alpha-MSH-like immunoreactivity in the cat central nervous system

The distribution pattern of alpha-melanocyte stimulating hormone-like immunoreactivity (alpha-MSH-Li) was studied in cats using avidin-biotin modification of immunocytochemical method. Cell bodies containing alpha-MSH-Li were observed in the medial basal hypothalamus, especially in the infundibular nucleus, the lateral hypothalamus and near zona incerta. Fibers with alpha-MSH-Li extended beyond the hypothalamus, into the paraventricular nucleus of the thalamus, rostral amygdala, periaqueductal gray, locus ceruleus, parabrachial nucleus and medial nucleus of the nucleus tractus solitarius. Axons with alpha-MSH-Li were also seen diffusely in various cortical areas, but more extensively in the limbic cortical regions. The distribution pattern of the cell bodies and fibers containing alpha-MSH-Li bears several similarities to that seen in rats, but differs in that the alpha-MSH-Li was not observed in cell bodies in locations other than the medial basal and lateral hypothalamus.