Spider neurotoxins block the beta scorpion toxin-induced calcium uptake in rat brain cortical synaptosomes.
In this paper we describe the effects of the beta scorpion toxin Tityus gamma (TiTX gamma) and spider neurotoxins Tx3-3 and Tx3-4 in the (45)Ca(2+) uptake in synaptosomes. The TiTX gamma-stimulatory effect on (45)Ca(2+) uptake in synaptosomes was inhibited omega-Conotoxin MVIIC (omega-CgTX MVIIC) (0.1 microM) and omega-Agatoxin IVA (0.1 microM) by 70% and 41%, respectively. omega-CgTX MVIIC (1.0 microM) almost completely blocked the TiTX gamma-induced (45)Ca(2+) uptake in synaptosomes. Verapamil (1.0 microM) and omega-Conotoxin GVIA (0.1 microM) had no effect in the scorpion toxin-induced (45)Ca(2+) influx. The spider neurotoxins Tx3-3 and Tx3-4 inhibited the TiTX gamma-induced calcium uptake with an IC(50) 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-induced calcium uptake involves P/Q-type calcium channels.
Miranda
D M
DM
Laboratírio de Neurofarmacologia, Departamento de Farmacologia, ICB-UFMG, MG, Belo Horizonte, Brazil.
Romano-Silva
M A
MA
Kalapothakis
E
E
Diniz
C R
CR
Cordeiro
M N
MN
Moraes-Santos
T
T
De Marco
L
L
Prado
M A
MA
Gomez
M V
MV
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D004347:Drug Interactions / Q000502:physiology*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009479:Neuropeptides / Q000494:pharmacology; D009498:Neurotoxins / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000494:pharmacology*; D013111:Spider Venoms / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D009479:Neuropeptides; D009498:Neurotoxins; D012604:Scorpion Venoms; D013111:Spider Venoms; C119038:Ts-gamma neurotoxin; C098736:Tx3 neurotoxin; D002118:Calcium