The study was undertaken to assess the antihyperalgesia effect of BmK IT2, a sodium channel-specific ligand purified from the venom of Chinese scorpion Buthus martensi Karsch in rat by peripheral injection. The peripheral inflammation of rat was induced by carrageenan resulted in hyperalgesia to heat stimulus. The heat hyperalgesia was measured by paw withdrawal latency (PWL). PWL was increased to 272 +/- 18%, 217 +/- 19% and 186 +/- 16% of the control by application of 10 microl BmK IT2 at the concentration of 0.1, 0. 01 and 0.001 mg/ml in inflammatory rats, respectively. In contrast, PWL was enhanced to about 177 +/- 16%, 141 +/- 15% and 133 +/- 15% of the control at the same applied concentrations of BmK IT2 in normal rats. The results thus suggest that BmK IT2 can produce peripheral antihyperalgesia and antinociception, which might be attributed a pathway of modulating the sodium channels on nociceptor.