The long open time component from the εT264P mutant receptor activated by 1 μM physostigmine (circles) was estimated at -100, -75, -50, -25 and +50 mV membrane potentials. No voltage-sensitivity was observed. For control, we estimated the open interval durations from the εT264P mutant receptor activated by 100 μM carbachol (squares) at -50 and +50 mV membrane potentials. Carbachol-elicited openings showed a voltage sensitivity of 93 mV per e-fold change. This value is similar to previous estimates for the wild type receptor and a number of mutant receptors activated by nicotinic agonists (Auerbach et al., 1996; Akk and Steinbach, 2000). Points show mean ± SD for data from 3 to 6 patches.