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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)|
Dal Belo, CA
|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.|
|Editor:||Pergamon-elsevier Science Ltd|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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