DISTRIBUTION OF SOMATOSTATIN RECEPTOR-1, RECEPTOR-2 AND RECEPTOR-3 MESSENGER-RNA IN RAT-BRAIN AND PITUITARY

In this study sequence-specific antisense oligonucleotide probes have been used to investigate the distribution of the mRNAs coding for the somatostatin receptor subtypes termed somatostatin receptor 1, somatos tatin receptor 2 and somatostatin receptor 3 in the rat brain and pitu itary using in situ hybridization techniques. The three receptor subty pe mRNAs were found to be widely distributed in the brain with differe nt patterns of expression, but with some overlap. Somatostatin recepto r 1 mRNA was particularly concentrated in the cerebral and piriform co rtex, magnocellular preoptic nucleus, hypothalamus, amygdala, hippocam pus, and several nuclei of the brainstem. Somatostatin receptor 3 mRNA was very abundant in the cerebellum and pituitary (in contrast to som atostatin receptor 1), but it was also found in hippocampus, amygdala, hypothalamus and in motor nuclei of the brainstem. Somatostatin recep tor 2 mRNA levels were very low relative to the other two mRNAs evalua ted. Receptor 2 mRNA was observed in the anterior pituitary, and in th e brain it was found in the medial habenular nucleus, claustrum, endop iriform nucleus, hippocampus, some amygdala nuclei, cerebral cortex an d hypothalamus. None of the three somatostatin receptor mRNAs studied here was found in the caudate nucleus. Northern analysis revealed dist inct sizes of mRNAs for each subtype, and displacement experiments sho wed that each probe sequence was subtype-specific.