Figure 4.

Glutamate excitation by subsurface application of glutamate in normal retinas depended on the proximity of RGCs to ejection sites, whereas latency of excitatory responses depended on RGC type. The majority (17/21) of cells recorded less than 130 μm from subsurface ejection sites were excited by glutamate. Most (five of six) cells recorded >130 μm from ejection sites were not affected by glutamate ejections (symbols, top). The latency of responses to glutamate varied considerably, with little dependence on the distance between ejection and recording sites. The average latency of responses (right) was significantly longer for OFF than ON cells, although the distribution of latencies did overlap. The average latency of suppression was shorter than excitation of OFF and ON cells. Arrows, latency of excitation in units that exhibited an initial suppression of firing.