Fig. 1.

NH₄Cl alters neuromuscular transmission in the mouse, human and pig intestine. Electrical field stimulation (EFS; 20 V, 0.3 ms, 2-30 Hz) frequency-response curves for neurogenic contractions and relaxations in segments of ileum and jejunum from mice (A), humans (B), and pigs (C) in the presence (red) or absence (black) of NH₄Cl (5 mM). Contractions (A, B, and C) and relaxations (Aii, Bii, and Cii) driven by EFS are abolished in the presence of tetrodotoxin (TTX; 0.3 μM; green). Ai, Bi, and Ci: dose-response curves showing the effect of ascending concentrations of NH₄Cl on contractions driven by 20-Hz EFS in mice, humans and pigs. EC₅₀ values for NH₄Cl are given for each at right. Data are means ± SE and were analyzed by two-way ANOVA and Bonferonni’s post hoc test. *P < 0.05, **P < 0.01 vs. control (n = 5 in each group).