Spider neurotoxins block the beta scorpion toxin-induced calcium uptake inrat brain cortical synaptosomes

In this paper we describe the effects of the P scorpion toxin Tityus gamma (TiTX gamma) and spider neurotoxins Tx3-3 and Tx3-4 in the Ca-45(2+) uptake in synaptosomes. The TiTX gamma -stimulatory effect on Ca-45(2+) uptake in synaptosomes was inhibited omega -Conotoxin MVIIC (omega -CgTX MVIIC) (0.1 muM) and omega -Agatoxin IVA(0.1 muM) by 70% and 41%, respectively, omega -CgTX MVIIC (1.0 muM) almost completely blocked the TiTX gamma -induced Ca- 45(2+) uptake in synaptosomes. Verapamil (1.0 muM) and w-Conotoxin GVIA (0. 1 muM) had no effect in the scorpion toxin-induced Ca-45(2+) influx. The sp ider neurotoxins Tx3-3 and Tx3-4 inhibited the TiTX gamma -induced calcium uptake with an IC50 of 10.0 and 30.0 nM, respectively. It is suggested that spider neurotoxins Tx3-3 and Tx3-4 blocking effect in the TiTX gamma -indu ced calcium uptake involves P/Q-type calcium channels. (C) 2001 Elsevier Sc ience Inc.