Enkephalin-like immunoreactivity in neurons in the human pineal gland.

Adult human pineal glands were prepared for immunohistochemical analysis using antisera against Leu-enkephalin, neuropeptide Y, dopamine-beta-hydroxylase and vasoactive intestinal polypeptide. The material shows small neurons located in septae and along the capsule of the gland which exhibit enkephalin-like immunoreactivity. The neurons have fairly extensive dendritic arbors and immunoreactive axons are present in the septae and beneath the capsule, particularly in a perivascular location, and occasionally extend into lobules of the gland among parenchymal cells. No consistent immunoreactivity was observed with other antisera but bundles of axons exhibiting dopamine-beta-hydroxylase or neuropeptide Y-like immunoreactivity are observed in some of the material in a perivascular location.