Immunocytochemical analysis of the rat pineal gland using antisera generated against analogs of luteinizing hormone-releasing hormone (LHRH).

Antisera generated against synthetic luteinizing hormone-releasing hormone (LHRH) or analogs of LHRH, agonists and antagonist, were used to stain the rat pineal gland and the median eminence of the hypothalamus. Of the LHRH analogs used, two revealed immunoreactive material in median eminence and not pineal, two stained pineal only, and three stained median eminence and pineal. Our observations suggest that the immunoreactive material in the pineal gland may be an LHRH-like substance whose affinity characteristics are different from that of hypothalamic LHRH. The affinity properties of hypothalamic LHRH for antibody appear to reside in the C-terminus of the molecule, whereas binding of the antigen in the pineal to antibody appear to be influenced by an N-terminal modification of the LHRH molecule.