NEUROTOXINS can help the understanding of mechanisms involved in neurotransmission. We here report that two neurotoxin isoforms, Tx3-3 and Tx3-4 obtained from the venom of the spider Phoneutria nigriventer inhibited the 45 Ca2+ influx in rat cortical synaptosomes induced by the scorpion venom tityustoxin. The IC50 for Tx3-3 and Tx3-4 were 0.32 and 7.9 nM, respectively. The neurotoxins Tx3-3 and Tx3-4 are very effective in inhibiting 45 Ca2+ influx and they should be useful in studies involving Ca2+ -dependent processes.
1Laboratório de Neurofarmacologia, Departmento de Farmacologia, ICB-UFMG, Av. Antonio Carlos 6627, 31270-901 Belo Horizonte-MG, Brasil
2Funed-Fundacao Ezequiel Dias
3Faculdada de Farmácia UFMG, Brasil
4Corresponding Author: Marcus Vinicius Gomez
ACKNOWLEDGEMENTS: This work was supported by grants of FAPEMIG, FINEP, PADCT, PRONEX and CNPq. We thank Dr L.A. De Marco for reading and suggestions on this manuscript and Miss A.A. Pereira, Miss A.G. Alves and Mr A.C.S. Gomes for technical assistance.
Received 16 February 1998; accepted 19 February 1998