Trans-synaptic regulation of growth and development of adrenergic neurones in a mouse sympathetic ganglion

Abstract

Summary The development of transmitter enzymes and the formation of synaptic connections have been studied in mouse superior cervical ganglion in vivo . Ganglion choline acetyl transferase (ChAc) activity increased by 40-fold during development and described a hyperbolic curve with time. Tyrosine hydroxylase (T-OH) activity rose in two separate and distinct phases during maturation. Estimates of total synapses per ganglion were obtained electron microscopically after staining with ethanolic phosphotungstic acid. Ganglion synapses increased 500-fold during development. From plateau levels during the first few days of life, synapse numbers increased markedly between days 5 and 11 to reach an asymptotic plateau. The developmental curve for ChAc was virtually congruent with that of synapse numbers, suggesting that increased enzyme activity reflected the maturation of preganglionic cholinergic terminals. On the other hand, the major increase in T-OH activity occurred synchronously with the marked increase in synapses, suggesting that the formation of synaptic contacts might be necessary for T-OH activity development. To examine this possibility ganglia were unilaterally decentralized in neonatal mice. Surgical transection of the preganglionic nerve trunk prevented normal development of T-OH activity in the postsynaptic adrenergic neurones. These observations indicate that presynaptic nerve terminals regulate the biochemical maturation of the postsynaptic adrenergic neurones.