title: Presynaptic action of Bothriopsis bilineata smargadina (forest viper) venom in vitro.
abstract: In this work, we examined the neuromuscular activity of Bothriopsis bilineata smargadina (forest viper) venom in vertebrate isolated nerve-muscle preparations. In chick biventer cervicis preparations the venom caused concentration-dependent (0.1-30 μg/ml) neuromuscular blockade that was not reversed by washing, with 50% blockade occurring in 15-90 min. Muscle contractures to exogenous acetylcholine and KCl were unaffected by venom, but there was a slight increase in creatine kinase release after 120 min (from 80 ± 15 to 206 ± 25U/ml, n=6, p<0.05). In mouse phrenic nerve-diaphragm preparations, the venom (1, 10 and 30 μg/ml) produced marked facilitation (∼120% increase above basal) at the highest concentration followed by neuromuscular blockade; the effects at lower concentrations were considerably less marked. Venom increased the quantal content values after 15 and 30 min followed by significant inhibition at ≥ 90 min. However, venom did not alter the muscle membrane resting potential or the response to exogenous carbachol. In both preparations, incubation at 22 °C instead of 37 °C delayed the onset of blockade, as did inhibition of venom PLA(2) activity. In curarized mouse preparations, the venom produced only muscle facilitation. These results indicate that B. b. smargadina venom causes neuromuscular blockade in vitro by a presynaptic mechanism involving PLA(2).
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), PO Box 6111, 13083-970 Campinas, SP, Brazil. simioni@unicamp.br
authors.forename: Léa
authors.initials: L
authors.lastname: Rodrigues-Simioni
authors.forename: Rafael Stuani
authors.initials: RS
authors.lastname: Floriano
authors.forename: Sandro
authors.initials: S
authors.lastname: Rostelato-Ferreira
authors.forename: Norma Cristina
authors.initials: NC
authors.lastname: Sousa
authors.forename: Sergio
authors.initials: S
authors.lastname: Marangoni
authors.forename: Luis Alberto
authors.initials: LA
authors.lastname: Ponce-Soto
authors.forename: Victor Corasolla
authors.initials: VC
authors.lastname: Carregari
authors.forename: Stephen
authors.initials: S
authors.lastname: Hyslop
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002645:Chickens; D003402:Creatine Kinase / Q000378:metabolism; D003964:Diaphragm / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects*; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D009469:Neuromuscular Junction / Q000187:drug effects*; D010791:Phrenic Nerve / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects; D014757:Viper Venoms / Q000494:pharmacology*; D017819:Viperidae
chemical_list: D009466:Neuromuscular Blocking Agents; D014757:Viper Venoms; D002217:Carbachol; D003402:Creatine Kinase; D000109:Acetylcholine