Unstimulated force was expressed as a percentage of the pre-fatigue peak tetanic force. Symbols:^, control wild-type; □, glibenclamide (10 μm) wild-type; ▵, control Kir6.2−/−; ⋄, glibenclamide (10 μm) Kir6.2−/− (inset). Vertical bars represent the s.e.m. of 5 wild-type and 6 Kir6.2−/− bundles. *Significantly different from control wild-type, ANOVA and lsd,P < 0.05.