Localization of naloxone-sensitive [³H]dihydromorphine binding sites within the hippocampus of the rat

In vitro radioautographic experiments were performed on coronal rat brain slices to determine the precise localization of [³H]dihydromorphine binding sites sensitive to naloxonem within the hippocampus. Binding was observed in all cel fields and in dentate gyrus (DG) in the order CA2 〉 CA1 〉 CA3 〉 DG. Within each cell field the density of receptors was greatest in the stratum pyramidale, which in field CA2 was 77% as dense as the striatum. The existence of a dense population of opiate binding sites within the hippocampus is consistent with the view that this structure is involved in opiate actions.