Figure 2.

Intrinsic light responses of M1 and M2 cells in whole-mount Opn4-EGFP mouse retinas. All light responses recorded in the presence of synaptic blockers and TTX. A, Left, EGFP signal under epifluorescent illumination of M1 (gray arrow) and M2 (white arrow) cell targeted for dual whole-cell current-clamp recordings. Right, Responses in current-clamp mode of M1 (gray trace) and M2 (black trace) cells shown in left panel to a 30 s white light stimulus. B, Left, EGFP signal under epifluorescent illumination of M1 (gray arrow) and M2 (white arrow) cell targeted for dual whole-cell voltage-clamp recordings. Right, Responses in voltage-clamp mode of M1 (gray trace) and M2 (black trace) cells shown in the left panel to a 30 s white light stimulus. C, Maximum depolarization evoked by single 30 s white light stimulus measured in current-clamp mode of M1 (gray; n = 17) and M2 (black; n = 19) cells. Mean depolarization of M1 (gray bar) and M2 (black bar) cells. D, Maximum current evoked by single 30 s white light stimulus measured in voltage-clamp mode of M1 (gray; n = 13) and M2 (black; n = 19) cells. Mean maximum current of M1 (gray bar) and M2 (black bar) cells. E, Brightness (in AUs) of epifluorescence of EGFP signal for pairs containing one M1 and one M2 cell. F, Irradiance response curves for M1 (gray; IR₅₀ ∼ 3.25 × 10¹² photons · cm⁻² · s⁻¹) and M2 (black; IR₅₀ ∼ 3.44 × 10¹³ photons · cm⁻² · s⁻¹) generated by stimulating cells with increasing intensities of a 5 s 480 nm light stimulus. G, Nucleated patch recordings were made in control solution from M2 cells (n = 5). H, I, Average of 5–7 light responses recorded from nucleated patches of two cells (cell 1, left panels; cell 2, right panels) in current-clamp mode to a fixed, bright 5 s (H) or 30 s (I) white light stimulus. J, Expanded view of first 1 s of 30 s light stimulation for cell 1 (left panel) and cell 2 (right panel). Scale bars: 50 μm. IR₅₀, Irradiance yielding half-maximal response.