PnTx3-6 a spider neurotoxin inhibits K super(+)-evoked increase in [Ca super(2+)] sub(i) and Ca super(2+)-dependent glutamate release in synaptosomes

• Published in: Neurochemistry international 2003-03, Vol.42 (4), p.277-282
• Main Authors: Vieira, L B, Kushmerick, C, Reis, HJ, Diniz, C R, Cordeiro, M N, Prado, MAM, Kalapothakis, E, Romano-Silva, MA, Gomez, M V
• Format: Article
• Language: English
• ISSN: 0197-0186
• DOI: 10.1016/S0197-0186(02)00130-4

The present experiments investigated the effect of a neurotoxin purified from the venom of the spider Phoneutria nigriventer. This toxic component, P. nigriventer toxin 3-6 (PnTx3-6), abolished Ca super(2+)-dependent glutamate release with an IC sub(50) of 74.4 nM but did not alter Ca super(2+)-independent secretion of glutamate when brain cortical synaptosomes were depolarized by KCl (33 mM). This effect was most likely due to interference with the entry of calcium through voltage activated calcium channels (VACC), reducing the increase in the intrasynaptosomal free calcium induced by membrane depolarization with an IC sub(50) of 9.5 nM. We compared the alterations induced by PnTx3-6 with the actions of toxins known to block calcium channels coupled to exocytosis. Our results indicate that PnTx3-6 inhibition of glutamate release and intrasynaptosomal calcium involves P/Q type calcium channels and this toxin can be a valuable tool in the investigation of calcium channels.