Antihyperalgesia effect of BmK IT2, a depressant insect-selective scorpiontoxin in rat by peripheral administration

The study was undertaken to assess the antihyperalgesia effect of BmK IT2, a sodium channel-specific ligand purified from the venom of Chinese scorpio n Buthus martensi Karsch in rat by peripheral injection. The peripheral inf lammation of rat was induced by carrageenan resulted in hyperalgesia to hea t stimulus. The heat hyperalgesia was measured by paw withdrawal latency (P WL). PWL was increased to 272 +/- 18%, 217 +/- 19% and 186 +/- 16% of the c ontrol by application of 10 mul BmK IT2 at the concentration of 0.1, 0.01 a nd 0.001 mg/ml in inflammatory rats, respectively. In contrast, PWL was enh anced to about 177 +/- 16%, 141 +/- 15% and 133 +/- 15% of the control at t he same applied concentrations of BmK IT2 in normal rats. The results thus suggest that BmK IT2 can produce peripheral antihyperalgesia and antinocice ption, which might be attributed a pathway of modulating the sodium channel s on nociceptor. (C) 2000 Elsevier Science Inc.