LOCALIZATION OF KAPPA-OPIOID RECEPTOR MESSENGER-RNA IN NEURONAL SUBPOPULATIONS OF RAT SENSORY GANGLIA AND SPINAL-CORD

A partial cDNA encoding a kappa-opioid receptor was isolated and used to generate specific S-35-labeled probes to investigate the gene expre ssion of the kappa-opioid receptor in sensory, sympathetic and spinal neurons of the rat by in situ hybridization. A subpopulation of mainly small and medium-sized neurons within dorsal root and trigeminal gang lia expressed kappa-receptor mRNA, but no signal was detectable in the superior cervical ganglion. kappa-Receptor mRNA was distributed over neurons throughout the dorsal horn and in laminae VII/VII. Highest con centrations of positive neurons were seen in laminae I/II, dorsal lami na X and in the lateral spinal nucleus. alpha-Motoneurons and glial ce lls were not labeled. This distribution of kappa-receptor mRNA indicat es preferential functions of kappa-receptors in sensory signalling wit h particular importance to nociception.