Ionic mechanism of cholinergic inhibition in molluscan neurons.

Acetylcholine, the inhibitory transmitter to the so-called H-neurons of molluscs, produces its effect by increasing the permeability of the subsynaptic membrane to chloride ions. The change in permeability gives rise to a net influx of this anion, which hyperpolarizes the neuron. The presence of an outward pump of chloride ions is postulated to account for the required electrochemical gradient. The participation of potassium ions in this inhibitory phenomenon was not detected.