Crotalphine, a novel potent analgesic peptide from the venom of the South American rattlesnake Crotalus durissus terrificus

Abstract: We have shown that the venom of the South American rattlesnake Crotalus durissus terrificus induces a long-lasting antinociceptive effect mediated by activation of κ- and δ-opioid receptors. Despite being mediated by opioid receptors, prolonged treatment with the crotalid venom does not cause the development of peripheral tolerance or abstinence symptoms upon withdrawal. In the present study, we have isolated and chemically characterized a novel and potent antinociceptive peptide responsible for the oral opioid activity of this crotalid venom. The amino acid sequence of this peptide, designated crotalphine, was determined by mass spectrometry and corroborated by solid-phase synthesis to be <EFSPENCQGESQPC, where <E is pyroglutamic acid and the two cysteine residues forming a disulfide bond. This 14-amino-acid residue sequence is identical to the γ-chain sequence of crotapotin, a non-toxic component of this snake venom. Crotalphine, when orally administered (0.008–25μg/kg), induces antinociceptive effect in the prostaglandin E2- and carrageenin-induced mechanical hyperalgesia models in rats and in the hot-plate test in mice. Crotalphine was also effective when administered by intravenous (0.0032–0.04μg/kg) or intraplantar (s.c., 0.00006–0.3μg/paw) routes. In the mechanical hyperalgesia models, crotalphine shows a long-lasting (5 days) antinociceptive effect. d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr amide (CTOP) and N,N-diallyl-Tyr-Aib-Aib-Phe-Leu (ICI 174,864), antagonists of μ- and δ-opioid receptors, respectively, did not alter the antinociceptive effect of the peptide, whereas nor-binaltorphimine, an antagonist of κ-opioid receptors, blocked this effect. These results indicate that crotalphine induces antinociception mediated by activation of κ-opioid receptors and may contribute to the antinociceptive effect of the crotalid venom. [Copyright &y& Elsevier]