Antinociceptive and Anti-Inflammatory Effects of Recombinant Crotamine in Mouse Models of Pain

Crotamine, a toxin found in the venom of the South American rattlesnake Crotalus durissus terrificus, has been reported to have antinociceptive effects. We purified recombinant crotamine expressed in Escherichia coli and investigated its antinociceptive and anti-inflammatory effects using the hot-plate test, acetic-acid-induced writhing method, and formalin test in mice. Recombinant crotamine was administered intraperitoneally (0.04-1.2 mg kg^-1) or intraplantarly (0.9-7.5 μg 10 μL^-1) before the tests. The paw volume was measured with a plethysmometer. To evaluate the antagonistic and anti-inflammatory effects of naloxone, subcutaneous naloxone (4 mg kg^-1) or intraplantar naloxone (5 μg 10 μL^-1) was administered before recombinant crotamine. For tumor necrosis factor (TNF)-α assays, blood was drawn 3 h after formalin injection and measured using enzyme-linked immunosorbent assay. Intraperitoneal and intraplantar recombinant crotamine had antinociceptive and anti-inflammatory effects, neither of which were affected by pre-treatment with naloxone. The mean serum TNF-α levels were significantly lower in the intraperitoneal recombinant crotamine (0.4 and 1.2 mg kg^-1) or intraplantar (2.5 and 7.5 μg 10 μL^-1) recombinant crotamine groups than in the saline group and were not affected by naloxone pre-treatment. In conclusion, recombinant crotamine possesses significant antinociceptive and anti-inflammatory effects that do not appear to be related to the opioid receptor. The antinociceptive and anti-inflammatory effects of intraperitoneal or intraplantar recombinant crotamine are related to TNF-α.