Fig. 6.

Glutamate release is reduced during exposure to 10 mm caffeine. The time course of glutamate release from the retina prepared as a photoreceptor sheet is shown. These reduced preparations were depolarized with 20 mm KCl (gray bars) att = 0 min after stabilization in 2 mmKCl (white bars). In these experiments, glutamate release stabilized after 35 min in 20 mm KCl, which is when the first measurements were made. Glutamate release was markedly suppressed by caffeine added at t = 45 min (to 47% of control; black bars). Each barrepresents the glutamate content of 5 min samples of the perfusate. The effect of caffeine was reversible; during the washout (att = 65 min) a consistent rebound increase in glutamate release was observed (n = 15).