PRODUCTION OF ANTISERUM TO [D-ALA2]DELTORPHIN I AND ITS IMMUNOHISTOCHEMICAL APPLICATION TO THE MOUSE-BRAIN

ANTISERUM to haptenic [D-Ala2]deltorphin I (DADTI: Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2), a highly selective ligand for delta-opioid receptors, was produced in rabbits. By immunospot assay, the antiserum recognized 62.5 pmol DADTI but failed to react even with 4 nmol carrier protein of the immunogen. Although the antiserum reacted equally with an isomer [L-Ala2]deltorphin I, virtually no cross-reaction occurred with other analogues such as [D-Ala2]deltorphin II (Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2) and similar peptides lacking the C-terminal glycine amide. Therefore, the major epitope for immunorecognition appeared to be in the C-terminal region which is known to be the specific domain for delta-opioid receptor selectivity. Immunohistochemical study using this antiserum revealed positive neuronal structures in some specific systems of the mouse brain.