Figure 2.

RyR inhibition does not suppress photoreceptor light response or calcium current. A, Light response of a rod (dark trace) held in current clamp (I = 0) to a 2 s green light stimulus. Application of 100 μm ryanodine (gray trace) did not suppress the response to light but produced a slight increase in the overshoot at light offset (arrow). B, Light response of a cone (dark trace) held in current clamp (I = 0) to a 2 s red light stimulus. Application of 100 μm ryanodine (gray trace) did not suppress light response but increased the overshoot at light offset (arrow). C, A representative current–voltage relationship of calcium current recorded from rod photoreceptors (dark trace). The rod was held at −80 mV and ramped to 0 mV in 100 ms. Currents were measured by subtracting control traces from 100 μm Cd²⁺ substituted traces. No significant change was observed during application of 100 μm ryanodine (gray trace). D, Activation curves (g_normalized vs V) plotted by fitting current–voltage data to the Boltzmann equation (see Materials and Methods), yielding a V_1/2 of −33.4 mV (control, dark trace) compared with −32.9 mV (100 μm ryanodine, gray trace).