Fig. 6.

Glutamate transporters selectively limit spillover. A, B, The effects of zero (solid lines), 25 μm (dashed lines), or 5 μm (dotted lines) transporters on synaptic (A) and spillover (500 nm; B) NMDA receptor responses. Transporters were distributed uniformly outside the synaptic cleft; their concentrations are with respect to tissue volume. C, Release of a single vesicle does not saturate nearby transporters (present at 25 μm). Solid line, 200 nm; dotted line, 300 nm; dashed line, 500 nm; anddot-dashed line, 1 μm. Subsequent simulations, unless otherwise stated, are in the presence of 25 μmtransporters outside the synaptic cleft.