Autoradiography of [3H]beta-endorphin binding in brain

The autoradiographic regional localization of [3H]beta-endorphin binding in rat brain differed from that of either [3H]dihydromorphine or [3H]D-Ala2-D-Leu5-enkephalin. Comparisons were made from sequential sections through 3 regions of rat brain: striatum, hypothalamus/thalamus, and brainstem. [3H]beta-endorphin labeled some clusters as well as the subcallosal streak in the striatum, the nucleus accumbens, lamina IV of the cortex, medial regions of the thalamus, hippocampus, inferior colliculus, dorsal raphe, median raphe and pontine nuclei. White matter regions had little binding. Although many of these structures were also labeled with either [3H]dihydromorphine or [3H]D-Ala2-D-Leu5-enkephalin, the overall pattern of [3H]beta-endorphin labeling appeared unique, consistent with the proposal of central epsilon receptors.