Fig. 8. The concentration–response relationship of pyrogallol on 30 mm KCl-induced relaxation in the presence of atropine and guanethidine (nonadrenergic noncholinergic [NANC] relaxation) (A ), and the effect of superoxide dismutase (SOD; 200 U/ml) on 3 × 10⁻⁴m pyrogallol-induced inhibition of the NANC relaxation (B ) of strips from the lower esophageal sphincter. Pyrogallol concentration-dependently inhibited the NANC relaxation, and 3 × 10⁻⁴m pyrogallol-induced inhibition of the NANC relaxation was significantly reversed by pretreating with SOD. Each point or bar represents the mean from tissues from five (A ) and three (B ) animals; vertical lines show SD. N indicates the number of strips. **P < 0.01, significantly different from the value in the absence of pyrogallol. ‡P < 0.01, significantly different from the value in the presence of pyrogallol and in the absence of SOD.