Figure 2.

There are two kinetic components to EPSCs evoked by depolarizing steps applied to rods and cones. Increasing the duration (10 to 1000 ms) of depolarizing steps (-70 to -10 mV) applied to rods or cones caused a biexponential increase in the EPSC charge transfer measured in OFF bipolar and horizontal cells during paired recordings from retinal slices. Data from rod-driven cells are shown in A, and data from cone-driven cells are shown in B. Fits to short-duration steps are expanded in the in sets. Postsynaptic recordings were obtained from both OFF bipolar cells (rod driven, n = 5; cone driven, n = 6) and horizontal cells (rod driven, n = 3; cone driven, n = 6) in the presence of cyclothiazide (0.1 mm). Data from six of the rod-driven cells were used for a similar comparison by Thoreson et al. (2004). No differences were detected between response/duration relationships in OFF bipolar and horizontal cells when synaptically stimulated by the same type of photoreceptor. Charge transfer during the EPSC was integrated and normalized to the charge transfer evoked by a 500 ms depolarizing step. Data were fit with dual-exponential functions (rods, τ₁ = 27.5 ms, τ₂ = 954 ms; cones, τ₁ = 2.4 ms, τ₂ = 570 ms). Error bars represent SEM.