Mapping of somatostatin receptor localization in rat brain: forebrain and diencephalon

Using quantitative in vitro receptor autoradiography, minute distributions of 125I-Tyr11-somatostatin (SS)-14 binding sites were investigated in the rat forebrain and diencephalon. In the cerebral cortex, there was a high density of receptors observed in layers V-VI and a low density in layers I-IV. The entorhinal cortex displayed the highest receptor density of the cerebral cortices. The olfactory system had a high SS receptor density. The anterior olfactory nucleus, nucleus of the lateral olfactory tract, medial habenular nucleus and the basolateral amygdaloid nucleus showed moderate densities. In the limbic system, the CA1 and subiculum regions had high receptor densities. More detailed observations revealed high receptor densities in the oriens, radiatum and lacunosum layers and a much lower density in the pyramidal cell layer. The caudate putamen and substantia nigra showed low receptor densities, while the claustrum displayed the highest density of receptors in the rat brain. These data were not consistent with those of previous studies using 125I-SS-28 and 125I-201-995, which had shown that the high receptor density area in the basolateral amygdaloid group was identified as the lateral amygdaloid nucleus, and that the pyramidal cell layer in the hippocampus showed high receptor densities.