The interaction of NO and CO on K_Ca channels in vascular SMCs. (a) Representative recordings showing the modulation of K_Ca currents by the sequential application of SNP and CO (left panel) or CO and then SNP (right panel) to different outside-out membrane patches. The dashed lines beside each trace indicate the current level of closed channels. (b) Pretreatment of cell membrane with SNP for 10 minutes abolished the effect of subsequently applied CO on K_Ca currents. However, pretreatment of cell membrane with CO for 10 minutes did not eliminate the excitatory effect of SNP on K_Ca currents. Membrane potential, –30 mV. n = 5 (from at least two batches of cells) for each group. *P < 0.05.