Fig. 2. Effects of isoflurane on open probability (Po) of single sarcolemmal adenosine triphosphate–sensitive potassium channel. Channel activity was monitored at +40 mV in symmetrical 145 mm K+. ( A, left ) Single-channel records from an inside-out patch from a non–anesthetic preconditioning (APC) myocyte. Upper deflection indicates the levels of channel opening (O1 and O2) from the closed level (C). Corresponding amplitude histograms are shown in A, right . Isoflurane (0.5 mm) increased channel Po in a reversible manner. Blockade with 1 mm adenosine 5′-triphosphate (ATP) confirmed identity of adenosine triphosphate–sensitive potassium channel. ( B ) Summary data (mean ± SD) for isoflurane effect on non-APC channel Po (* P < 0.05, n = 18). ( C ) Baseline Po of APC channels was no different from Po of non-APC channels and was unaffected by secondary in vitro treatment with isoflurane (n = 12).