BACKGROUND AND OBJECTIVES: Histamine receptor antagonists affect pain perception. H1 receptor antagonists present local analgesic effect, but the role of H2 receptor antagonists on pain in the peripheral nervous system is not clear yet. This study aimed at evaluating the effects of different H2 receptor antagonists on pain induced by formalin paw injection in rats. METHOD: Male rats were studied and divided into groups that received formalin and different H2 receptor antagonists - ranitidine, cimetidine and loxtidine, injected in the paw at different concentrations (0.05 mol, 0.25 mol or 1 mol). The number of flinches was evaluated during 45 minutes. RESULTS: Loxtidine inhibited the number of flinches in both phases of the test with the three different concentrations. Ranitidine decreased the number of flinches in phase II as from 0.25 mol. Cimetidine did not affect pain behavior. CONCLUSION: According to the results of this study, some H2 receptor antagonists presented local analgesic effects, which seem to be drug-related and not pharmacological class-specific.
Cimetidine; Formalin; Loxtidine; Pain; Ranitidine; Rats
