A comparison of the long-term and short-term regulations of tyrosine hydroxylase activity

The activity of tyrosine hydroxylase, the enzyme that catalyzes the rate-limiting step in catecholamine biosynthesis, increases in postganglionic sympathetic neurons following electrical stimulation of their afferent preganglionic input. Two types of changes in enzyme activity occur: an acute increase and a delayed and long-lasting increase. The pharmacological mechanisms involved in these transsynaptic effects and the biochemical mechanisms underlying the changes in tyrosine hydroxylase activity are discussed.