HFS in the ferret thalamic slice results in glutamate release that is not blocked by the classic neuronal exocytosis inhibitor tetrodotoxin. HFS of the LGN (100Hz, 100μs pulse width, 300μA) for 10s in the in vitro ferret thalamic slice abolished spindles waves in the post-stimulation period (A, upper trace) and resulted in a concurrent increase in extracellular glutamate as measured by an enzyme-linked glutamate sensor (A, lower trace). After tetrodotoxin (TTX, 2μM) was applied to the bath, neuronal activity was abolished (B, upper trace); however, an increase in extracellular glutamate was still recorded by the glutamate sensor (B, lower trace). The stimulating electrode and the glutamate sensor electrode were positioned within ∼100μm of each other.