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Type: Artigo de periódico
Title: The neuromuscular activity of paradoxin: A presynaptic neurotoxin from the venom of the inland taipan (Oxyuranus microlepidotus)
Author: Hodgson, WC
Dal Belo, CA
Rowan, EG
Abstract: The inland taipan is the world's most venomous snake. However, little is known about the neuromuscular activity of the venom or paradoxin (PDX), a presynaptic neurotoxin from the venom. Venom (10 mu g/ml) and PDX (65 nM) abolished indirect twitches of the chick biventer cervicis and mouse phrenic nerve diaphragm preparations. The time to 90% inhibition by PDX was significantly increased by replacing Ca2+ (2.5 mM) in the physiological solution with Sr2+ (10 mM). In the biventer cervicis muscle, venom (10 mu g/ml), but not PDX (65 nM), significantly inhibited responses to ACh (1 mM) and carbachol (20 mu M), but not KCl (40 mM). In the mouse diaphragm (low Ca2+; room temperature), the inhibitory effect of PDX (6.5 nM) was delayed and a transient increase (746 +/- 64%; n = 5) of contractions observed. In intracellular recording experiments using the mouse hemidiaphragm, PDX (6.5-65 nM) significantly increased quantat content and immature endplate potential frequency prior to blocking evoked release of acetylcholine. In extracellular recording experiments using the mouse triangularis sterni, PDX (2.2-65 nM) significantly inhibited the voltage-dependent K+, but not Na+, waveform. In patch clamp experiments using B82 mouse fibroblasts stably transfected with rKv 1.2, PDX (22 nM; n = 3) had no significant effect on currents evoked by 10 mV step depolarisations from -60 to +20 mV. PDX exhibits all the pharmacology associated with beta-neurotoxins, and appears to be one of the most potent, if not the most potent beta-neurotoxin yet discovered. (c) 2007 Elsevier Ltd. All rights reserved.
Subject: neurotoxin
neuromuscular transmission
Country: Inglaterra
Editor: Pergamon-elsevier Science Ltd
Citation: Neuropharmacology. Pergamon-elsevier Science Ltd, v. 52, n. 5, n. 1229, n. 1236, 2007.
Rights: fechado
Identifier DOI: 10.1016/j.neuropharm.2007.01.002
Date Issue: 2007
Appears in Collections:Unicamp - Artigos e Outros Documentos

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