IMMUNOCYTOCHEMICAL LOCALIZATION OF DELTA-OPIOID RECEPTORS IN MOUSE-BRAIN

An affinity-purified anti-peptide antibody generated against the carbo xy-terminal region of the delta opioid receptor was used to localize d elta opioid receptors in mouse brain. delta Opioid receptor immunoreac tivity was found in axons and nerve terminals in regions of the olfact ory bulb, hippocampal formation, cerebral and cerebellar cortex, midbr ain and hindbrain. The immunocytochemical distribution correlated well , though not completely with autoradiographic distribution of delta op ioid receptors in mouse brain using either [H-3] [2-D-penicillamine, 5 -D-penicillamine]-enkephalin (DPDPE) or [H-3]naltrindole. Confocal mic roscopy of double-labeled tissue provided direct evidence that delta o pioid receptors are principally expressed on GABAergic terminals in th e hippocampus. These anatomical findings complement extensive physiolo gical studies to provide a more detailed description of endogenous opi oid circuitry.