TYROSINE HYDROXYLASE IN RAT BRAIN: DEVELOPMENTAL CHARACTERISTICS

Abstract

Abstract— The development of tyrosine hydroxylase (tyrosine 3‐hydroxylase, EC 1.14.3.a) activity has been examined in whole rat brain and in various regions and subcellular fractions thereof. The specific activity of tyrosine hydroxylase increased almost 15‐fold from 15 days of gestation to adulthood. With maturation, those regions of the brain that contain only terminals of the catecholaminergic neurons showed the greatest increases in enzyme activity. There was a shift in the subcellular distribution of tyrosine hydroxylase from the soluble fraction in the fetal brain to the synaptosomal fraction in the adult brain. Tyrosine hydroxylase, dopamine hydroxylase (EC 1.14.2.1) and the specific uptake mechanism for norepinephrine appear to develop in a coordinated fashion.