Abstract
Using specific antisera to human beta-lipotropin, we have visualized cells and axons with beta-lipotropin-like immunoreactivity in rat brain and pituitary. The beta-lipotropin so localized is well delineated and contained in the cytoplasm of cells and in beaded axons. Areas of greatest beta-lipotropin content are hypothalamus (with cell bodies in the medial basal hypothalamus and arcuate regions), periventricular nucleus of the thalamus, ansa lenticularis, zona compacta of the substantia nigra, medial amygdaloid nucleus, zona incerta, periaqueductal central gray area, locus ceruleus, and a few fibers in the reticular formation. The question of the exact relationship of beta-lipotropin and methionine-enkephalin remains open, because some brain areas contain both substances and some areas contain only one or the other.