Effects of pentobarbitone on acetylcholine‐activated channels in mammalian muscle

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Abstract
1 Acetylcholine-activated single channel currents were recorded from the extrajunctional region of chronically denervated skeletal muscle of the rat by the patch clamp technique. 2 In control experiments, the cumulative open-time, closed-time and burst length distributions could be well described by the sum of two exponentials. 3 Pentobarbitone decreased the mean open time and increased the time constant of the fast component of the closed time distribution. These effects increased with drug concentration. 4 The mean burst length was relatively independent of pentobarbitone concentration over the range of concentrations used (10–500 μM). 5 These observations are inconsistent with a simple sequential blocking model and it is suggested that pentobarbitone has an allosteric site of action on receptor-channel complexes that makes the open state less stable.