Species-specific expression of cholecystokinin messenger RNA in rodent dorsal root ganglia.

The expression of cholecystokinin (CCK) messenger RNA (mRNA) was examined in dorsal root ganglia of rat and guinea pig using in situ hybridization histochemistry and RNA (Northern) blot hybridization with synthetic oligodeoxyribonucleotide (oligomer) probes. In guinea pig, CCK mRNA was detected in small and medium-sized neuronal perikarya comprising approximately 10-15% of the total dorsal root ganglia cell population. In contrast, in neurons of rat dorsal root ganglia, CCK mRNA was not detectable. Northern blot analyses revealed a single CCK mRNA species of expected size (0.8 kb) in guinea pig, but not rat, dorsal root ganglia. A 0.8 kb CCK mRNA was, however, detected in cortex of both rat and guinea pig. These data suggest that CCK is normally not synthesized in neurons of rat dorsal root ganglia and that there are species differences in CCK gene expression in mammalian sensory ganglia.