Kinetics of agonist conductance changes during hyperolarization at frog endplates.

The effect of rapid hyperpolarization on acetylcholine- or carbachol-induced currents was studied at voltage clamped frog endplates. Following a hyperpolarizing step the agonist-induced conductance increased approximately exponentially to a new level. The rate constant for this process was smaller during hyperpolarization or lowered temperature, and was also smaller for acetylcholine than for carbachol. The results are interpreted in terms of a potential-dependent conformational change of the receptor.