Neuromuscular Activity of Micrurus laticollaris (Squamata: Elapidae) Venom in Vitro

Alejandro Carbajal-Saucedo,Alejandro Alagón,Rafael Floriano,Alejandro Olvera-Rodríguez,Cháriston Belo,Léa Rodrigues-Simioni

doi:10.3390/toxins6010359

Abstract

In this work, we have examined the neuromuscular activity of Micrurus laticollaris (Mexican coral snake) venom (MLV) in vertebrate isolated nerve-muscle preparations. In chick biventer cervicis preparations, the MLV induced an irreversible concentration- and time-dependent (1–30 µg/mL) neuromuscular blockade, with 50% blockade occurring between 8 and 30 min. Muscle contractures evoked by exogenous acetylcholine were completely abolished by MLV, whereas those of KCl were also significantly altered (86% ± 11%, 53% ± 11%, 89% ± 5% and 89% ± 7% for one, three, 10 and 30 µg of venom/mL, respectively; n = 4; p < 0.05). In mouse phrenic nerve-diaphragm preparations, MLV (1–10 µg/mL) promoted a slight increase in the amplitude of twitch-tension (3 µg/mL), followed by neuromuscular blockade (n = 4); the highest concentration caused complete inhibition of the twitches (time for 50% blockade = 26 ± 3 min), without exhibiting a previous neuromuscular facilitation. The venom (3 µg/mL) induced a biphasic modulation in the frequency of miniature end-plate potentials (MEPPs)/min, causing a significant increase after 15 min, followed by a decrease after 60 min (from 17 ± 1.4 (basal) to 28 ± 2.5 (t15) and 12 ± 2 (t60)). The membrane resting potential of mouse diaphragm preparations pre-exposed or not to d-tubocurarine (5 µg/mL) was also significantly less negative with MLV (10 µg/mL). Together, these results indicate that M. laticollaris venom induces neuromuscular blockade by a combination of pre- and post-synaptic activities.

Highlights

Coral snakes constitute a taxonomic assemblage of more than 120 species and subspecies [1,2,3] distributed from the southern United States to southern South America, achieving their greatest abundance of species in lower latitudes [4], and they are, together with the pelagic sea snake, Pelamis platurus, the American representatives of the family, Elapidae [5,6]
Micrurus laticollaris venom (1–30 μg/mL) caused irreversible time- and concentration-dependent neuromuscular blockade in indirectly stimulated biventer cervicis (BC) preparations, with complete blockade occurring from 20 min at the highest concentration (30 μg/mL) (Figure 1A)
The muscle-type nicotinic receptors are distributed alongside the muscle fiber characterizing the multiple neuromuscular junctions [26]

Summary

Introduction

Coral snakes (formally included in the genera, Micrurus, Leptomicrurus and Micruroides) constitute a taxonomic assemblage of more than 120 species and subspecies [1,2,3] distributed from the southern United States to southern South America, achieving their greatest abundance of species in lower latitudes [4], and they are, together with the pelagic sea snake, Pelamis platurus, the American representatives of the family, Elapidae [5,6] Their venoms contain low-molecular mass neurotoxins of the three-finger type, which block the neuromuscular junction by binding with high affinity to the cholinergic receptor at the neuromuscular junction, promoting a paralytic effect [7,8,9,10]. We investigated the neuromuscular activity of the crude venom from the Mexican coral snake, M. laticollaris

Results and Discussion

Venom and Animals

Twitch-Tension Experiments

Intracellular Recordings

Statistical Analysis

Conclusions