Expression of cholecystokinin and enkephalin mRNA in discrete brain regions.

The levels of preprocholecystokinin mRNA were measured in several regions of rat brain using RNA blot analysis. In both species, high levels of expression were observed in the thalamus, amygdala, neocortical areas and hippocampus. Intermediate levels were observed in the periaqueductal grey, hypothalamus, substantia nigra, ventral tegmental area, and olfactory bulbs; little or no mRNA was detected in the caudate nucleus, nucleus accumbens, olfactory tubercle, cerebellum or a liver control. In contrast, the caudate and olfactory tubercle expressed large amounts of preproenkephalin mRNA. Other regions, such as the periaqueductal grey and olfactory bulbs, expressed both transcripts while regions like the hippocampus contained prominent amounts of preprocholecystokinin mRNA and relatively little preproenkephalin mRNA.