Effects of SNP and CO on the whole-cell KCa currents generated by heterologous expression of KCa,α subunit in COS-1 cells. Membrane potential was stepped with 600-ms duration from –80 to +60 mV in 10-mV increments from a holding potential of –80 mV at 0.1 Hz. (a) The cells transfected with GFP cDNA alone did not yield KCa currents. (b) KCa currents were recorded in COS-1 cells transiently cotransfected with GFP and mSlo cDNAs. (c) SNP had no effect on the mSlo-encoded KCa currents (n = 8 from three batches of cell preparations). The inset shows the original current traces at +50 mV. (d) CO significantly increased the mSlo-encoded KCa currents (n = 5 from three batches of cell preparations). The inset shows the original current traces at +50 mV. *P < 0.05 vs. control. nA, nanoampere.