Figure 3 :Effect of i.c.v. injection of ranitidine on the numbers of writhes induced by acetic acid in rats. Each column represents mean ± SEM (n = 6 rats for normal saline, six rats for histamine, six rats for chlorpheniramine plus histamine, and six rats for ranitidine plus histamine). *P < 0.05 vs. other groups (one-way ANOVA followed by Duncan's test), i.c.v.: intracerebroventricular.