Small injections of the retrograde fluorescent tracer Fast blue into different cortical areas, including the hippocampal region, labeled cells in the zona incerta and the lateral hypothalamic area. A majority (approximately equal to 90%) of the retrogradely labeled cells cross-reacted with an anti-serum to the opioid peptide alpha-melanocyte stimulating hormone (alpha-MSH). Sequential staining of the same tissue sections showed that a majority of the alpha-MSH stained cells in the lateral hypothalamic area and the zona incerta also contain the enzyme acetylcholinesterase (AChE) but not cholineacetyltransferase. These results suggest that cortical AChE resides partly in non-cholinergic terminals and that some of these arise from alpha-MSH immunoreactive cells in the hypothalamus and subthalamus.