DIFFERENTIAL EXPRESSION OF SOMATOSTATIN RECEPTORS BY QUANTITATIVE PCRIN THE RAT-BRAIN

Five subtypes of somatostatin receptors (sst) have recently been clone d and reported to be expressed in rat brain. However, conventional mRN A measurement techniques do not allow to accurately compare the levels of expression of the 5 sst. Thus, we established a quantitative rever se transcriptase polymerase chain reaction method for the 5 sst. A cRN A internal standard was constructed by inserting in msst1 plasmid sequ ences corresponding to specific sense printers for amplification of ea ch sst. Using a common reverse primer, a unique primer pair by recepto r amplifies both wild type and standard RNAs with the same efficiency. The technique was validated by evaluating sst mRNAs in 3 brain struct ures in which different somatostatin receptor binding levels were prev iously reported. While the absolute level of expression is similar bet ween regions, sst3 is the major subtype in cerebellum, sst1 predominat es in spinal cord and sst4 and sst2 are equally expressed in the hypot halamus.