Further investigations on the effect of denervation and pH on the conductance change at the neuromuscular junction of the frog.

Currents induced by acetylcholine application at the voltage-calmped frog end-plate, were measured over a large range of membrane potentials. Due to a non-linearity of the current-voltage curve, the directly-measured reversal potential may be quite different from the value classically determined by extrapolation (linear regression) of the measurements made at potentials below spike threshold. Denervation and changes of external pH were found to alter the shape of the current-voltage relation, but not the directly-measured reversal potential. These effects are tentatively explained on the basis of changes in the ratio: time-to-peak for [ACh] reaching the receptors/mean life-time of the open synaptic channels. Possible changes in cooperativity are also considered.