1. Tx3-4 a toxin from the venom of spider Phoneutria nigriventer blocks calcium channels associated with exocytosis.
- Author
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de Castro Junior CJ, Pinheiro AC, Guatimosim C, Cordeiro MN, Souza AH, Richardson M, Romano-Silva MA, Prado MA, and Gomez MV
- Subjects
- Animals, Brain ultrastructure, Calcium Channel Blockers pharmacology, Dose-Response Relationship, Drug, Male, Neuropeptides pharmacology, Potassium Chloride pharmacology, Rats, Rats, Wistar, Synaptosomes drug effects, Calcium Channels drug effects, Exocytosis drug effects, Neurotoxins pharmacology, Spider Venoms pharmacology
- Abstract
The purpose of the present work was to investigate the pharmacological action of a calcium channel-blocking toxin from the venom of the spider Phonetic nigriventer, Tx3-4 on calcium channels coupled to exocytosis of synaptic vesicles. Tx3-4 blocked KCl-induced exocytosis of synaptic vesicles with an IC50 of 1.1 nM. To investigate whether the target of Tx3-4 overlaps with known calcium channels that mediate calcium entry and exocytosis, we used omega-toxins that interact selectively with neuronal calcium channels. The results indicate that the main population of voltage-sensitive calcium channels altered by Tx3-4 is P/Q calcium channels. In conclusion, Tx3-4 is a potent inhibitor of calcium channels involved in the KCl-induced exocytosis of synaptic vesicles in brain cortical synaptosomes.
- Published
- 2008
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