Neuromuscular activity of the venoms of the Colombian coral snakes Micrurus dissoleucus and Micrurus mipartitus: An evolutionary perspective

• Published in: Toxicon (Oxford) 2012-01, Vol.59 (1), p.132-142
• Main Authors: Renjifo, Camila, Smith, Eric N., Hodgson, Wayne C., Renjifo, Juan M., Sanchez, Armando, Acosta, Rodrigo, Maldonado, Jairo H., Riveros, Alain
• Format: Article
• Language: English
• Subjects: Animal poisons toxicology. Antivenoms; Animals; antivenoms; Biological and medical sciences; Chick biventer cervicis; Chickens; Diseases of striated muscles. Neuromuscular diseases; Elapid Venoms - chemistry; Elapid Venoms - pharmacology; Elapidae; humans; In Vitro Techniques; mechanism of action; Medical sciences; Micrurus; Muscle Contraction - drug effects; Myotoxic; Neostigmine - pharmacology; Neurology; Neuromuscular Junction - drug effects; Neurotoxic; Phospholipase A2 Inhibitors; Phylogeny; potassium chloride; tissues; Toxicology; Venom; venoms
• ISSN: 0041-0101; 1879-3150
• DOI: 10.1016/j.toxicon.2011.10.017

The venoms of coral snakes (genus Micrurus) are known to induce a broad spectrum of pharmacological activities. While some studies have investigated their potential human effects, little is known about their mechanism of action in terms of the ecological diversity and evolutionary relationships among the group. In the current study we investigated the neuromuscular blockade of the venom of two sister species Micrurus mipartitus and Micrurus dissoleucus, which exhibit divergent ecological characteristics in Colombia, by using the chick biventer cervicis nerve-muscle preparation. We also undertook a phylogenetic analysis of these species and their congeners, in order to provide an evolutionary framework for the American coral snakes. The venom of M. mipartitus caused a concentration-dependant inhibition (3–10 μg/ml) of nerve-mediated twitches and significantly inhibited contractile responses to exogenous ACh (1 mM), but not KCl (40 mM), indicating a postsynaptic mechanism of action. The inhibition of indirect twitches at the lower venom dose (3 μg/ml) showed to be triphasic and the effect was further attenuated when PLA2 was inhibited. M. dissoleucus venom (10–50 μg/ml) failed to produce a complete blockade of nerve-mediated twitches within a 3 h time period and significantly inhibited contractile responses to exogenous ACh (1 mM) and KCl (40 mM), indicating both postsynaptic and myotoxic mechanisms of action. Myotoxic activity was confirmed by morphological studies of the envenomed tissues. Our results demonstrate a hitherto unsuspected diversity of pharmacological actions in closely related species which exhibit divergent ecological characteristics; these results have important implications for both the clinical management of Coral snake envenomings and the design of Micrurus antivenom. ► We investigated the bioactivity of the venom of Micrurus mipartitus and Micrurus dissoleucus. ► The venom of M. mipartitus caused concentration-dependant postsynaptic inhibition. ► M. dissoleucus venom caused both postsynaptic and myotoxic mechanisms of action. ► Results demonstrate diversity of pharmacological actions in related species. ► Important implications clinical management of envenomings and design of antivenom.