Development of neurons synthesizing noradrenaline and acetylcholine in the superior cervical ganglion of the rat in vivo and in vitro

Abstract

The development of neurons synthesizing noradrenaline and acetylcholine in the superior cervical ganglion of the rat has been examined after transection of the preganglionic nerve trunk in vivo and by maintenance of whole ganglia in modified Rose chambers in vitro. Temporal changes in the activities of two neurotransmitter enzymes, tyrosine hydroxylase and choline acetyltransferase, were measured as markers for neurons synthesizing noradrenaline and acetylcholine, respectively. In vivo, there was a small increase in choline acetyltransferase activity between birth and adulthood and this was comparable to the increase seen in ganglia from 2-day-old rats maintained in vitro for 14 days in the absence of nerve growth factor. Both in vivo and in vitro, high doses of nerve growth factor (10 μg/g and 1 μg/ml, respectively) resulted in increases in both tyrosine hydroxylase activity and choline acetyltransferase activity, the effect on choline acetyltransferase activity being greater in vitro than in vivo. Similar concentrations of nerve growth factor had no effect on the choline acetyltransferase activity in cultured ganglia taken from 3-week-old rats. It is concluded that increases in choline acetyltransferase activity occur only in ganglia from newborn rats because they contain neurons that still retain flexibility of development and can synthesize acetylcholine due to the influence of factors within the ganglion or in the culture medium. In vitro, following the elimination of endogenous nerve growth factor by the addition of anti-nerve growth factor, tyrosine hydroxylase activity decreased but choline acetyltransferase activity increased in cultured ganglia. High concentrations of guanethidine (100 μg/ml) caused decreases in both tyrosine hydroxylase and choline acetyltransferase activities. Following removal of guanethidine from the medium, choline acetyltransferase activity increased but tyrosine hydroxylase activity was unchanged. When guanethidine was replaced with nerve growth factor, tyrosine hydroxylase activity increased to a greater extent than choline acetyltransferase activity. Our results are discussed in terms of the presence in the ganglion of a multipotential cell type which can differentiate into either an adrenergic or a cholinergic neuron. Differentiation along cholinergic lines is accompanied by a loss of the ability to take up catecholamines and a release from dependence on nerve growth factor. Show more