SCREENING OF SNAKE-VENOMS FOR NEUROTOXIC AND MYOTOXIC EFFECTS USING SIMPLE IN-VITRO PREPARATIONS FROM RODENTS AND CHICKS

Eight snake venoms designated by the WHO as International Reference Ve noms, and one additional venom were assessed for neurotoxic and myotox ic effects in vitro using the chick biventer cervicis and the rat and mouse phrenic nerve-diaphragm preparations. The objective was to deter mine whether any of the preparations could be used to detect evidence of neurotoxic or myotoxic activity prior to a more detailed examinatio n. Bungarus multicinctus venom at concentrations above 1 mug ml-1 sele ctively blocked neuromuscular transmission, with no direct effect on m uscle fibres. Naja naja kaouthia and Notechis scutatus venoms selectiv ely blocked neuromuscular transmission at low concentrations, but at h igher concentrations both venoms caused direct effects on skeletal mus cle resulting in contractures, loss of tension following direct stimul ation and a loss in sensitivity to elevated [K+]0. Vipera russelli (Th ailand) venom also blocked neuromuscular transmission but it was less potent than the venoms of B. multicinctus, N. n. kaouthia and N. scuta tus. It also caused contractures in the chick biventer cervicis muscle . The venoms of Echis carinatus (Iran and Mali), Crotalus atrox, Bothr ops atrox asper and Trimeresurus flavoviridis had limited neuromuscula r blocking activity, and most of these venoms blocked [K+]0 and cholin oceptor stimulation in the chick muscle. Although both chick and roden t muscles allowed the assessment of neurotoxic and myotoxic activity, the chick biventer cervicis was simpler and more robust in use than ei ther of the rodent phrenic nerve-diaphragm preparations. We propose th at the chick biventer cervicis muscle could be used as a standard prep aration for the screening of snake venoms for neurotoxic and myotoxic effects, and that it may be possible to use this preparation as a mean s to check that antivenoms can neutralize neurotoxic and direct myotox ic actions of venoms.