Time course of the development of enzymes involved in the synthesis of norepinephrine in the superior cervical ganglion of the rat from birth to adult life

Abstract The general growth of the rat superior cervical ganglion and the development of enzymes specific for its preganglionic cholinergic and postganglionic adrenergic neurons have been studied from birth to 75 days of age. The total protein content, taken as a measure of general growth, increased 2.5-fold from birth to adulthood and approached its maximum at 20 days of age. The increase in the activity of choline acetyltransferase, which is selectively located in preganglionic cholinergic nerves and which is biochemical correlate for the formation of synapses, amounted to 50-fold for total and to 15-fold for specific activity. The maximum was reached at 30 days of age. The increase in the activity of the enzymes characteristics of the adrenergic neurons was much smaller. The maximal increase in the specific activity of tyrosine hydroxylase amounted to only 40% and was already reached 10–14 days after birth. The specific activity of dopamine β-hydroxylase increased 2.5-fold, but the maximum was not reached before 40 days of age. The activity of DOPA decar☐ylase, the third enzymes involved in the synthesis of norepinephrine, increased virtually in parallel with the general growth of the ganglia. The importance of the nerve growth factor and the activity of preganglionic nerves for the normal development of postganglionic adrenergic neurons are discussed in connection with previous studies which showed that both nerve growth factor in new-born rats and increased preganglionic activity in adult rats produce a selective induction of tyrosine hydroxylase and dopamine β-hydroxylase in adrenergic neurons.