Figure 1.

Citrate potentiates ASIC-dependent pain behavior. A–C, Each mouse was injected with either PBS, pH 7.4 (A, C), or citrate, pH 7.4 (B) in one hindpaw and then PBS, pH 5.5 (A); or citrate, pH 5.5 (B); or citrate, pH 7.4 (C), in the other hindpaw, or vice versa. The presence (+) or absence (o) of a withdrawal reflex was recorded; n = 4–6 per group, n.s. p > 0.05, *p < 0.05, two-tailed Mann–Whitney U test, in which (+) was ranked as 1 and (o) was ranked as 0. D–F, Each mouse was injected in either hindpaw with PBS, pH 7.4 or 5.5, as described for A–C, with or without amiloride (100 μm). The presence (+) or absence (o) of a withdrawal reflex was recorded; n = 4–14 per group, n.s. p > 0.05, ***p < 0.001, two-tailed Mann–Whitney U test, in which (+) was ranked as 1 and (o) was ranked as 0. G, Each mouse was injected with PBS, pH 5.5, in one hindpaw and then citrate, pH 5.5 (25 mm), in the other hindpaw, or vice versa. The relative withdrawal intensity between the two hindpaws was compared and recorded: (+) for greater, (=) for equivalent, and (−) for lesser withdrawal response; n = 7 per group, *p < 0.05, two-tailed Mann–Whitney U test, in which (+) was ranked as +1, (=) was ranked as 0, and (−) was ranked as −1. H, Summary of the results from Figure 1. n.s., Not significant.