IN-SITU HYBRIDIZATION STUDY OF MU-OPIOID AND KAPPA-OPIOID RECEPTOR MESSENGER-RNAS IN THE RAT SPINAL-CORD AND DORSAL-ROOT GANGLIA

Distributions of mu- and kappa-opioid receptor mRNAs in the lumbar spi nal cord and dorsal root ganglia of the adult rat were examined using the in situ hybridization technique. In the lumbar spinal cord, mu-opi oid receptor mRNA was expressed intensely in laminae I, II and VIII. O n the other hand, kappa-opioid receptor mRNA was expressed intensely i n laminae I and II, and moderately throughout laminae III-VIII. In the dorsal root ganglia, mu-opioid receptor mRNA was intensely expressed and kappa-opioid receptor mRNA was expressed in a smaller number of ce lls than mu-opioid receptor mRNA.