Fig. 4. Treatment with isoflurane enhances sensitivity of human atrial sarcolemmal adenosine triphosphate-sensitive potassium channel to pinacidil in mid-aged (MA) and old-aged (OA). Whole cell recordings of sarcolemmal adenosine triphosphate-sensitive potassium channel current were made from MA and OA myocytes. Current was monitored over time by stepping every 15 s to 0 mV from a holding potential of −40 mV for 200 ms. Pinacidil-activated current was measured in MA and OA myocytes in control (  A and  B ) and after cell exposure to isoflurane and washout (  C and  D ). With or without isoflurane treatment, current activation by pinacidil was greater in MA than in OA. BASE = baseline; GLIB = 1 μm glibenclamide; ISO = 0.5 mm isoflurane; PIN = 30 μm pinacidil. (  E ) Summary data from experiments shown above. Values are mean ± SD.  P < 0.05: * ISO/PIN  versus PIN in MA and OA; # PIN in OA  versus PIN in MA and ISO/PIN in OA  versus ISO/PIN in MA.