Ontogeny of cholecystokinin gene expression in the rat thalamus--a hybridization histochemical study

We examined the ontogeny of cholecystokinin (CCK) gene expression in the rat thalamus using hybridization histochemistry. Maturation of CCK gene expression occurred over the course of a month, beginning in the medial geniculate nucleus on the 17th day of gestation. CCK mRNA was found in the caudal nuclei first, later in the rostral; the ventral were followed by the dorsal; and the lateral by the medial. In some nuclei, such as the medial geniculate, CCK mRNA was present prior to the full differentiation of the neurons; whereas in others, such as the mediodorsal, the neurons differentiated to almost adult morphology before CCK mRNA was detected.