ETHANOL ALONE OR WITH DEXAMETHASONE ALTERS THE KINETICS OF CHOLINE-ACETYLTRANSFERASE

Choline acetyltransferase activity was measured in rats treated with d aily injections of ethanol (0.1 g/kg body wt) and or dexamethasone (1 mg/kg body wt) for 5 consecutive days. Ethanol produced a biphasic red uction of choline acetyltransferase activity in rat cerebral cortex, w hich at most time points was further decreased by simultaneous injecti on of dexamethasone. Kinetic studies of cortex choline acetyltransfera se activity in rats that had received 5 daily injections of ethanol or ethanol and dexamethasone indicated that the observed reduction in en zyme activity was due to an apparent reduction in affinity (K-m) of th e enzyme for acetyl coenzyme A with no significant change in the total amount of enzyme present (V-max). This finding has implications with respect to the use of choline acetyltransferase as a marker for cholin ergic neurons, and for the understanding of the regulation of choline acetyltransferase activity in the brain.