Neurotoxicity of Micrurus altirostris (Uruguayan coral snake) venom and its neutralization by commercial coral snake antivenom and specific antiserum raised in rabbits

Abstract

In this work, we studied the neuromuscular blockade caused by Micrurus altirostris venom (0.1–10 μg/mL) in indirect stimulated chick biventer cervicis and mouse phrenic nerve-diaphragm preparations and the ability of commercial antivenom (Instituto Butantan) and antiserum raised in rabbits to neutralize neurotoxicity and lethality in chicks and mice (LD₅₀ 0.042 and 0.255 mg/kg), injected i.m. and i.p., respectively, with venom (5 LD₅₀):antivenom or antiserum mixtures (n = 6) of 1:1-1:2.5-1:5-1:10-1:20. The venom caused a complete and irreversible neuromuscular blockade in both preparations, inhibited the acetylcholine and carbachol contractures, without interfering on KCl response. The neuromuscular blockade was not Ca²⁺ or temperature-dependent and did not affect the response to direct stimulation. Only a venom:antivenom or antiserum ratio of 1:20 neutralized the neuromuscular blockade in vitro and protected chicks and mice against 5 LD₅₀ of venom. Our results indicated that Micrurus altirostris venom interferes with postsynaptic neurotransmission and that commercial antivenom and rabbit antiserum have low efficacy in neutralizing the neurotoxicity and lethality of this venom.

Keywords: :

• Antivenom
• Blockade
• Neurotransmission
• Neutralization
• Postsynaptic neurotoxin

Acknowledgments

The authors thank José Ilton dos Santos for technical assistance. This research was supported by the Brazilian agency CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico).