Abstract

After treatment of rats with reserpine, the in vitro activity of choline acetyltransferase increased in the stellate and superior cervical ganglia and in the adrenal gland. This enzyme is confined to preganglionic nerve terminals, as demonstrated for the latter two organs. The increase was dose-dependent and persisted for three days after a single dose of the drug. Choline acetyltransferase activities in preparations from reserpinetreated and control animals were additive and the K_m for substrate and for cofactor were not changed after reserpine treatment. These observations indicate that the increase in enzyme activity is not due to the disappearance of an inhibitor, to the formation of an activator or to an alteration of the active site but rather to an increase in the number of active sites. This increase in enzyme activity was prevented by concomitant administration of cycloheximide, indicating that the rise is dependent on protein synthesis. Transection of the spinal cord at the level of the 5th thoracic vertebra completely prevented the rise in activity of choline acetyltransferase in the adrenal glands. It is concluded that a prolonged increase in the activity of the fibers supplying the preganglionic cholinergic neurons of the peripheral sympathetic nervous system leads to an induction of choline acetyltransferase in the latter.