Immunocytochemical evidence that the same neurons in the human infundibular nucleus are stained with anti-endorphins and antisera of other related peptides.

Neurons immunoreactive with anti-beta-endorphin can be detected in the infundibular region of human fetal hypothalami from the 11th week of development. In the human adult, neurons stained with anti-beta-endorphin are located in the infundibular nucleus and are also stained with anti(17-39) ACTH. Their fibers terminate in contact with non/immunoreactive perikarya or close to vessels of the pituitary stalk. The neurons most reactive with anti(17-39)ACTH or anti-beta-endorphin are also immunoreactive with anti-alpha-MSH, anti-beta-MSH, anti-alpha-endorphin, anti(1-24)ACTH or anti-beta-LPH. These results suggest that a molecule similar to pro-opiocortin of fragment(s) of it is secreted by these neurons.