Nitric oxide activation of a potassium channel (BKCa) in feline lower esophageal sphincter

Figure 5 Effect of sodium nitroprusside (10^-4 mol/L) ± iberiotoxin (10^-7 mol/L), and iberiotoxin (10^-7 mol/L) ± sodium nitroprusside (10^-4 mol/L) on smooth muscle tone relative to basal tone in the presence of tetrodotoxin (10^-6 mol/L) in muscle strips of lower esophageal sphincter (A) circular (n = 6) and (B) sling (n = 6-9) muscles. A: In lower esophageal sphincter (LES) circular muscle, sodium nitroprusside (SNP) decreased the resting tension and this tension was then unchanged with further addition of iberiotoxin (IbTX) (P > 0.05). When IbTX was added first, there was no significant change in tension, while the subsequent addition of SNP [IbTX+SNP in the presence of tetrodotoxin (TTX)] significantly decreased the tension (P < 0.001); B: In LES sling muscle, SNP or SNP+IbTX decreased the tension to the same extent, and IbTX alone produced no significant change in resting tension. IbTX+SNP decreased the tension (P < 0.001). //: Separates different experiments. ^bP < 0.001.