Fall in choline acetyltransferase activity in the ventricles of the rat heart after treatment with a ganglion blocking drug.

The choline acetyltransferase activity was found to be 27% lower in the ventricles of rats which had been given the ganglion blocking drug chlorisondamine than in those of untreated rats. Since the weight of the ventricles were also lower in the treated rats than in the untreated ones, it was wondered whether a change in the muscle mass as such affected the activity of the enzyme: isoprenaline treatment was found to cause the weight to increase markedly, while it left the enzyme activity unchanged. The decrease in enzyme activity observed after the prolonged ganglion blockade is interpreted as being the consequence of a reduced traffic of impulses along the postganglionic parasympathetic nerves of the ventricles. Thus, the results of the present investigation give further support for the ideal of a vagal innervation of this part of the heart.