Activation of tyrosine hydroxylase during electrical stimulation of isolated nerve endings of the rat hypothalamus

Abstract

The effect of electrical stimulation on synaptosomal membrane-bound tyrosine hydroxylase (TH) activity in the rat hypothalamus was investigated. Electrical stimulation intensified respiration and glycolysis, evidence of excitation of the synaptosomes. Against this background, activity of membrane-bound TH was increased. The value of Km for tyrosine fell from 0.091 to 0.026 mM. Inhibition of the enzyme activity by the end product of cathecholamine biosynthesis (noradrenalin) was reduced. It is postulated that the effect of depolarization on the rate of catecholamine synthesis in nerve endings is effected through modification of TH.