In Vitro Neurotoxicity of Chinese Krait () Venom and Neutralization by Antivenoms.

, the Chinese krait, is a highly venomous elapid snake which causes considerable morbidity and mortality in southern China. venom contains pre-synaptic PLA neurotoxins (i.e., β-bungarotoxins) and post-synaptic neurotoxins (i.e., α-bungarotoxins). We examined the in vitro neurotoxicity of venom, and the efficacy of specific monovalent Chinese antivenom, and Australian polyvalent elapid snake antivenom, against venom-induced neurotoxicity. venom (1-10 μg/mL) abolished indirect twitches in the chick biventer cervicis nerve-muscle preparation as well as attenuating contractile responses to exogenous ACh and CCh, but not KCl. This indicates a post-synaptic neurotoxic action but myotoxicity was not evident. Given that post-synaptic α-neurotoxins have a more rapid onset than pre-synaptic neurotoxins, the activity of the latter in the whole venom will be masked. The prior addition of Chinese antivenom (12 U/mL) or Australian polyvalent snake antivenom (15 U/mL), markedly attenuated the neurotoxic actions of venom (3 μg/mL) and prevented the inhibition of contractile responses to ACh and CCh. The addition of antivenom (60 U/mL), or Australian polyvalent snake antivenom (50 U/mL), at the t time point after the addition of venom (3 μg/mL), did not restore the twitch height over 180 min. The earlier addition of antivenom (60 U/mL), at the t or t time points, also failed to prevent the neurotoxic effects of the venom but did delay the time to abolish twitches based on a comparison of t values. Repeated washing of the preparation with physiological salt solution, commencing at the t time point, failed to reverse the neurotoxic effects of venom or delay the time to abolish twitches. This study showed that venom displays marked in vitro neurotoxicity in a skeletal muscle preparation which is not reversed by antivenom. This does not appear to be related to antivenom efficacy, but due to the irreversible/pseudo-irreversible nature of the neurotoxins.