Figure 11.
Characterization of transretinal ERG responses from five mouse lines. Absolute response amplitudes as a function of flash strength were obtained from PND14–16 Rho+/+, RhoP23H/+, RhoP23H/P23H (A), Gnat1−/−RhoP23H/P23H and Gnat2cpfl3/cpfl3RhoP23H/P23H (B) mouse retinas. Points were fitted with Naka-Rushton hyperbolic functions for Rho+/+ (n = 9), RhoP23H/+ (n = 6), RhoP23H/P23H (n = 12), Gnat1−/−RhoP23H/P23H (n = 11) and Gnat2cpfl3/cpfl3RhoP23H/P23H (n = 11) retinas. The intensity–response relationship also is shown as purple triangles in (A) for RhoP23H/P23H retinas treated with 130 µm 11-cis-retinal for 1 h at room temperature prior to recording (n = 6). (C) Amplification of the phototransduction cascade in mouse photoreceptors. Population-averaged dim flash responses to light intensities of 14 photons μm−2 (for Rho+/+ and RhoP23H/+ retinas), 392 photons μm−2 (for RhoP23H/P23H and Gnat1−/−RhoP23H/P23H retinas) and 1.1 × 104 photons μm−2 (for Gnat2cpfl3/cpfl3RhoP23H/P23H retinas) were normalized to their corresponding maximum dark voltages, Rmax. Then, fractional responses were scaled down by factors of 1 (RhoP23H/+ and Gnat2cpfl3/cpfl3RhoP23H/P23H) or 8 (RhoP23H/P23H and Gnat1−/−RhoP23H/P23H) to make all initial rising phases coincide with that of the Rho+/+ response. Light intensities corresponding to these scaled responses were thus determined as 14/1 = 14 photons μm−2 (RhoP23H/+), 392/8 = 49 photons μm−2 (RhoP23H/P23H and Gnat1−/−RhoP23H/P23H) and 1.1 × 104/1 = 1.1 × 104 photons μm−2 (Gnat2cpfl3/cpfl3RhoP23H/P23H). (D) Kinetics of dim flash responses in mouse photoreceptors. Normalized population-averaged dim flash responses demonstrate the accelerated response inactivation in RhoP23H/+, RhoP23H/P23H and Gnat2cpfl3/cpfl3RhoP23H/P23H mouse retinas.