Glutamate measurements made in the in vitro ferret thalamic slice demonstrate that HFS-induced glutamate release is vesicular and calcium-dependent. (A) Tetrodotoxin (TTX) treatment has no effect on glutamate release. (B) HFS-induced glutamate release is suppressed by treatment with the calcium chelator, BAPTA-AM (50μM, 1h; n=3). (C) Bath application of Bafilomycin (1μM, 45min; n=9), an inhibitor of vacuolar type H+-ATPase, in addition to TTX, resulted in inhibition of glutamate release. (D) The anion-channel blocker NPPB (100μM, 10min), does not inhibit HFS-induced glutamate release in the thalamic slice. The stimulating electrode and the glutamate sensor electrode were positioned within ∼100μm of each other.