Bothropstoxin-I reduces evoked acetylcholine release from rat motor nerve terminals: Radiochemical and real-time video-microscopy studies
| Autor: | Cicília de Carvalho, Andreimar M. Soares, Paulo Correia-de-Sá, M.A. Timóteo, Walter L.G. Cavalcante, Márcia Gallacci, José Bernardo Noronha-Matos, Patrícia Isabel Marques, Fátima Ferreirinha |
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| Rok vydání: | 2013 |
| Předmět: |
Male
End-plate potential Diaphragm Presynaptic Terminals Neuromuscular transmission Pyridinium Compounds Biology Toxicology Inhibitory postsynaptic potential Exocytosis Postsynaptic potential Crotalid Venoms medicine Animals Myocyte Bothrops Rats Wistar Fluorescent Dyes Motor Neurons Neuromuscular Blockade Microscopy Video L-Lactate Dehydrogenase Myography Skeletal muscle Acetylcholine Rats Phrenic Nerve Quaternary Ammonium Compounds Phospholipases A2 medicine.anatomical_structure Biochemistry Biophysics Female medicine.symptom Microelectrodes Muscle Contraction Muscle contraction |
| Zdroj: | Toxicon. 61:16-25 |
| ISSN: | 0041-0101 |
| DOI: | 10.1016/j.toxicon.2012.10.014 |
| Popis: | Understanding the biological activity profile of the snake venom components is fundamental for improving the treatment of snakebite envenomings and may also contribute for the development of new potential therapeutic agents. In this work, we tested the effects of BthTX-I, a Lys49 PLA2 homologue from the Bothrops jararacussu snake venom. While this toxin induces conspicuous myonecrosis by a catalytically independent mechanism, a series of in vitro studies support the hypothesis that BthTX-I might also exert a neuromuscular blocking activity due to its ability to alter the integrity of muscle cell membranes. To gain insight into the mechanisms of this inhibitory neuromuscular effect, for the first time, the influence of BthTX-I on nerve-evoked ACh release was directly quantified by radiochemical and real-time video-microscopy methods. Our results show that the neuromuscular blockade produced by in vitro exposure to BthTX-I (1 μM) results from the summation of both pre- and postsynaptic effects. Modifications affecting the presynaptic apparatus were revealed by the significant reduction of nerve-evoked [3H]-ACh release; real-time measurements of transmitter exocytosis using the FM4-64 fluorescent dye fully supported radiochemical data. The postsynaptic effect of BthTX-I was characterized by typical histological alterations in the architecture of skeletal muscle fibers, increase in the outflow of the intracellular lactate dehydrogenase enzyme and progressive depolarization of the muscle resting membrane potential. In conclusion, these findings suggest that the neuromuscular blockade produced by BthTX-I results from transient depolarization of skeletal muscle fibers, consequent to its general membrane-destabilizing effect, and subsequent decrease of evoked ACh release from motor nerve terminals. |
| Databáze: | OpenAIRE |
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