Differential expression of five somatostatin receptor subtypes, SSTR1-5, in the CNS and peripheral tissue.

Somatostatin regulates endocrine and exocrine secretion, acts as a neurotransmitter/neuro-modulator and possesses antiproliferative properties. These diverse physiological effects are mediated by G-protein coupled receptors of which at least five subtypes have been cloned (SSTR1-5). Here, we have investigated the tissue distribution pattern of mRNAs encoding the five SRIF receptor subtypes in the adult rat by RT-PCR analysis and in situ hybridization histochemistry. All five receptor subtypes were found to be expressed simultaneously in brain and pituitary by RT-PCR. Besides, the in situ hybridization results clearly show a distinct but overlapping expression pattern of SSTR1-5 mRNA in the central nervous system as was found by RT-PCR for the periphery. Such distinct SRIF receptor expression may contribute to the selective biological functions of the receptor subtypes.