Fig. 10.

The effect of normal and pH-adjusted PBS solution and α,β-meATP on mechanical hyperalgesia in rats. a Time–response curves of the effect of intraplantar (i.pl.) phosphate-buffered saline (PBS) or α,β-meATP (50 nmol) dissolved in PBS injected into the right hind paw at a volume of 100 µl/paw on the baseline mechanical paw withdrawal threshold (PWT). Each point represents mean ± S.E.M. of the PWT in pressure as a percentage of baseline % applied to the hind paw before (pre) and after PBS/α,β-meATP administration, obtained from the indicated number of rats. α,β-meATP decreased PWT both pH and time dependently post injection (repeated measures ANOVA time × treatment effect F_1,38 = 1.760, P < 0.00001). The changes from baseline PWT were at pH 7.4, 16.5% (P = 0.0026, n = 6), at pH 7.0, 25.6% (P = 0.001, n = 6), at pH 6.5, 33.3% (P < 0.001, n = 6, one-way ANOVA followed by the Dunnett test) at 1 h. For the sake of clarity, statistical significance is not indicated in the figure. b Dose-dependent effect of α,β-meATP on mechanical hyperalgesia at pH 7.0. ^§P < 0.05; statistically significant difference vs. baseline; *P < 0.05; statistically significant difference vs. PBS. Results were analyzed by repeated measures ANOVA, followed by Neuman–Keuls test, n = 6–10 animals per group. c The effect of acidification on α,β-meATP-induced hyperalgesia. PWT values were normalized to the response obtained by 50 mM α,β-meATP at pH 7.4. *P < 0.05; statistically significant difference from the 100%. Results were analyzed by one-way ANOVA followed by Tukey test, n = 6 animals per group