Neuromuscular activity of Micrurus laticollaris (Squamata: Elapidae) venom in vitro.
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.
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, CP. 62210, Mexico. micropechis@yahoo.com.mx.
Alejandro
A
Carbajal-Saucedo
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, CP. 62210, Mexico. floriano_rs@yahoo.com.
Rafael Stuani
RS
Floriano
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, CP. 62210, Mexico. charistondb@gmail.com.
Cháriston André
CA
Dal Belo
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, CP. 62210, Mexico. aolvera@ibt.unam.mx.
Alejandro
A
Olvera-Rodríguez
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, CP. 62210, Mexico. alagon@ibt.unam.mx.
Alejandro
A
Alagón
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, CP. 62210, Mexico. simioni@unicamp.br.
Léa
L
Rodrigues-Simioni
D000818:Animals; D002645:Chickens; D004546:Elapid Venoms / Q000494:pharmacology*; D017815:Elapidae; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018482:Muscle, Skeletal / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000378:metabolism; D010791:Phrenic Nerve / Q000187:drug effects; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects
D004546:Elapid Venoms; D011978:Receptors, Nicotinic