Increased acetylcholine synthesis and release following presynaptic activity in a sympathetic ganglion

The acetylcholine (ACh) content of sympathetic ganglia increases above its normal level following a period of preganglionic nerve stimulation. In the present experiments, this extra ACh that accumulates following activity was labeled radioactively from [3H]choline and its specific activity was compared with that of ACh subsequently released during preganglionic nerve stimulation. The specific activity released ACh was similar to that of the total tissue ACh, suggesting that the extra ACh mixes fully with endogenous stores. The present experiments also show that transmitter release during neuronal stimulation is necessary for the poststimulation increase in transmitter store, However, the increase was not evident when transmitter release was induced by K+. It is concluded that both transmitter release and impulse invasion of the nerve terminals are necessary for the adaptive phenomenon to manifest itself. The role of choline delivery and choline acetyltransferase activity in generating the poststimulation increase in transmitter store was tested. When choline transport activity measured as choline analogue (homocholine) accumulation increased. ACh synthesis was increased and when transport activity was not increased, neither was ACh synthesis. There was no poststimulation increase in measured choline acetyltransferase activity.