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|Title:||Neuromuscular activity of Micrurus laticollaris (Squamata: Elapidae) venom in vitro|
|Author:||Dal Belo, C. A.|
Floriano, R. S.
|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 mu g/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 mu g of venom/mL, respectively; n = 4; p < 0.05). In mouse phrenic nerve-diaphragm preparations, MLV (1-10 mu g/mL) promoted a slight increase in the amplitude of twitch-tension (3 mu g/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 mu g/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 (t(15)) and 12 +/- 2 (t(60))). The membrane resting potential of mouse diaphragm preparations pre-exposed or not to d-tubocurarine (5 mu g/mL) was also significantly less negative with MLV (10 mu g/mL). Together, these results indicate that M. laticollaris venom induces neuromuscular blockade by a combination of pre-and post-synaptic activities|
|Appears in Collections:||FCM - Artigos e Outros Documentos|
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