Preprocholecystokinin mRNA in rat brain: regional expression includes thalamus

The regional distribution of forebrain neurons expressing preprocholecystokinin (preproCCK) mRNA was examined using in situ and blot hybridization analysis. We observed a distribution of neurons containing preproCCK mRNA closely parallel to that reported for CCK immunoreactivity, with the exception of the thalamus. In this CCK-immunoreactive cell body-poor structure, we detected relatively abundant RNA: probe hybridization using both our techniques. Control experiments suggested that the hybridizing species in thalamus is authentic preproCCK mRNA. This suggests that there exist forebrain neurons expressing the CCK gene which have gone undetected in immunocytochemical studies.