Neuromuscular activity of Micrurus laticollaris (Squamata: Elapidae) venom in vitro

• Published in: Toxins Vol. 6; no. 1; pp. 359 - 370
• Main Authors: Carbajal-Saucedo, Alejandro, Floriano, Rafael Stuani, Dal Belo, Cháriston André, Olvera-Rodríguez, Alejandro, Alagón, Alejandro, Rodrigues-Simioni, Léa
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 17.01.2014; MDPI
• Subjects: Animals; Chickens; Elapid Venoms - pharmacology; Elapidae; In Vitro Techniques; Male; Membrane Potentials - drug effects; Mice; Micrurus; Micrurus laticollaris; Muscle, Skeletal - drug effects; Neuromuscular Junction - drug effects; Neuromuscular Junction - metabolism; neuromuscular preparations; Phrenic Nerve - drug effects; postsynaptic action; presynaptic action; Receptors, Nicotinic - drug effects; Receptors, Nicotinic - metabolism; snake venom; Squamata; Synaptic Transmission - drug effects
• ISSN: 2072-6651; 2072-6651
• DOI: 10.3390/toxins6010359

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.