Minimum duration of trans synaptic stimulation required for the induction of tyrosine hydroxylase by reserpine in the rat superior cervical ganglion

—The period during which trans-synaptic stimulation is required by the rat superior cervical ganglion for induction of tyrosine hydroxylase by reserpine has been studied. Ganglia were decentralized on one side at various times before or after an injection of reserpine. The tyrosine hydroxylase activity of the denervated and control ganglia was assayed 72 h after drug treatment. When decentralization was performed 8 h after an injection of reserpine the increase in tyrosine hydroxylase activity was blocked in the denervated ganglia. Decentralization 12 h after reserpine treatment or later had no effect on the enzyme induction. The actual increase in tyrosine hydroxylase activity occurred between 24 and 48 h after injection of reserpine.