Fig. 5. Effects of 30 min hypoxia alone and in combination with other agents on the activity of sarcolemmal K_ATP channels in cell-attached patches. Channel open state probability (P_o) was significantly increased in response to hypoxia, a response that was maximal after 20 min (N=8; mean ± 1 S.E.M.) and reversible upon the return of normoxic solution (washout). The inset shows a representative recording of K_ATP channel activity from a single experiment; after only 10 min hypoxia, the number of active channels/patch was substantially increased. Channel openings are shown as upward deflections in response to depolarization by 80 mV; c, all channels closed. Simultaneous application of hypoxia and BDM (N=4), or hypoxia and an inhibitor of NO-sensitive guanylate cyclase (ODQ; 20 µmol l^-1; N=6), eliminated the hypoxia-induced increase in channel activity. Hypoxia plus an inhibitor of NO synthase (L-NAME; 50 µmol l^-1; N=4) reduced the magnitude of the increase in P_o seen with 20 min hypoxia alone. ^*, significantly different from normoxia (P<0.05).