ω-Agatoxin IVA TFA is a potent, selective P/Q type Ca 2+ (Cav2.1) channel blocker with IC 50 s of 2 nM and 90 nM for P-type and Q-type Ca 2+ channels , respectively. ω-Agatoxin IVA TFA ( IC 50 , 30-225 nM) inhibits glutamate exocytosis and calcium influx elicited by high potassium. ω-Agatoxin IVA TFA also blocks the high potassium-induced release of serotonin and norepinephrine. ω-Agatoxin IVA TFA has no effect on L-type or N-type calcium channels [1] [2] .