Dissociation of Stimulatory and Synthetic Phases in the Induction of Tyrosine Hydroxylase

Abstract

RESERPINE treatment causes an increase in the activity of tyrosine hydroxylase (T-OH) in the superior cervical ganglion of the rat. A single systemic injection of the drug produces a rise in enzyme activity that reaches a maximum 48–72 h later¹. No change in T-OH is seen if the preganglionic cholinergic tract is cut at the time of reserpine administration or if animals are pretreated with the ganglion blocking agents pempidine or chlorisondamine^2,3. In the cat, direct electrical recording from the preganglionic cervical sympathetic trunk has revealed increased neuronal firing after reserpine administration⁴. These findings suggest that the rise in T-OH activity elicited by reserpine is mediated trans-synaptically through an increase in ganglionic transmission.