Tx3-4 a toxin from the venom of spider Phoneutria nigriventer blocks calcium channels associated with exocytosis.
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.
de Castro Junior
Célio José
CJ
Departamento Farmacologia BeloHorizonte, MG, Brazil. celiojcjunior@yahoo.com.br
Pinheiro
Ana Cristina N
AC
Guatimosim
Cristina
C
Cordeiro
Marta N
MN
Souza
Alessandra H
AH
Richardson
Michael
M
Romano-Silva
Marco A
MA
Prado
Marco Antônio M
MA
Gomez
Marcus V
MV
D000818:Animals; D001921:Brain / Q000648:ultrastructure; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis / Q000187:drug effects*; D008297:Male; D009479:Neuropeptides / Q000494:pharmacology; D009498:Neurotoxins / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013111:Spider Venoms / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D009479:Neuropeptides; D009498:Neurotoxins; D013111:Spider Venoms; C098736:Tx3 neurotoxin; D011189:Potassium Chloride