Figure 6. Physiological properties of ChR2 channels during long-term expression in mouse ganglion cells. A: The cell was held at V_hold=−60 mV in voltage-clamp mode (VC, upper panel). ChR2-currents were elicited by light stimuli (Nicon B-3A fluorescence filter) with light intensities ranging from 2.5×10¹⁴ to 8.2×10¹⁸ photons cm⁻²s⁻¹. During the same experiment in the current-clamp mode (CC, lower panel), the cell was held at −60 mV by I_hold=−10 pA current injection. B: Normalized currents were plotted against light intensity. In VC, the half-maximal peak current was reached at 2.1×10¹⁷ photons cm⁻²s⁻¹ and in CC the half-maximal peak potential at 3.2×10¹⁶ photons cm⁻²s⁻¹. Scale bars 1 s and 300 pA for VC and 1 s and 20 mV for CC.