DIFFERENCES IN THE DEVELOPMENTAL EXPRESSION OF THE VESICULAR ACETYLCHOLINE TRANSPORTER AND CHOLINE-ACETYLTRANSFERASE IN THE RAT-BRAIN

The neurotransmitter acetylcholine (ACh) is synthesized by the enzyme choline acetyltransferase (ChAT) and then transported into synaptic ve sicles by the vesicular acetylcholine transporter (VAChT). Since the V AChT gene is located within the first intron of the ChAT gene, it is l ikely that expression of the two genes is coregulated. We compared the developmental expression of VAChT and ChAT mRNA and protein in rat br ain. ChAT mRNA and enzyme activity increased by almost 10-fold from em bryonic day 19 to adulthood, with the most pronounced increase occurri ng after birth. In contrast, VAChT mRNA increased by only about 2-fold from late embryonic stages to adult levels. However, VAChT protein fo llowed the developmental pattern of ChAT activity, revealing a large e xcess of VAChT mRNA over VAChT protein during early stages of developm ent. The results are suggestive of differential mechanisms of ChAT and VAChT regulation during brain development, and of possible translatio nal control of VAChT expression.