THE ABILITY OF SPECIFIC ANTIVENOM AND LOW-TEMPERATURE TO INHIBIT THE MYOTOXICITY AND NEUROMUSCULAR BLOCK INDUCED BY MICRURUS-NIGROCINCTUS VENOM

In the isolated mouse diaphragm preparation, Micrurus nigrocinctus ven om produced a dose-dependent contracture and blockade of the contracti le response to direct and indirect electrical stimulation of the muscl e. This effect could not be completely reversed by repeated washing of the preparation nor by the addition of neostigmine or 3,4-diaminopyri dine, The observation that the direct blockade had to be preceded by i ndirect blockade together with the capacity of the venom to prevent th e ACh- but not the KCl-induced contractures in biventer cervicis and c hronically denervated preparations strongly suggests a curarimimetic a ction for the venom. The temperature at which the experiment was perfo rmed greatly influenced the neuromuscular blocking and myotoxic action s of the venom and suggests that the venom component responsible for t hese effects is thermolabile. Both the neuromuscular blocking action a nd the myotoxicity of the venom could be prevented by a specific M. ni grocinctus antivenom regardless of whether this was added together wit h or after the venom. The muscle morphological changes induced by the venom were accompanied by a corresponding increase in the release of c reatine kinase (CK) into the incubation medium. This release was, howe ver, submaximal (35%) when compared to that induced by the detergent T riton X-100. In contrast to what has been demonstrated for other Micru rus venoms (M. frontalis, M. corallinus, M. lemniscatus and M. spixii) , our results show that the myotoxic effect induced by M. nigrocinctus venom is important for the development of irreversible blockade of th e muscle contractile response.