Rod and cone contributions to the ERG depend on postnatal age. The developmental progression of the mouse ERG. (A) Both WT and Gnat1−/− photoreceptor responses emerge at P8 and increase rapidly in amplitude thereafter. Photoreceptor-driven a-waves at P8, P9, and P10 evoked by green (520 nm) flashes of increasing intensity (delivering 0.19–13,280 photons µm−2) presented at t = 0 (green arrow). Cone responses obtained from Gnat1−/− animals were evoked by the light of increasing intensity (delivering 379–83,835 photons µm−2) without background saturation. The rod-driven nose component emerges at P9 (black arrow) and becomes more robust at P10. Inset: Cone-evoked responses at P10 isolated under the stimulus protocol from Fig. 1. (B) In emergent time points, the dynamic range of the retina is compact at P8. This remains consistent until adulthood. The sensitivity, however, increases by ∼1 log unit with each passing day in development. Population averaged a-wave amplitudes plotted as a function of flash intensity, from P10 (triangle, n = 12), P9 (circle, n = 8), and P8 (square, n = 10) retinas. (C) Outer retinal signaling increases at a slower rate between eye opening and maturity. Response families to the same stimuli used in A from P14 (left) and adult (right) retinas. Insets represent Gnat1−/− a-waves at corresponding time points without background saturation. Retinas were initially perfused with Locke’s media containing BaCl2 to observe both the negative-going photoreceptor component and the positive-going bipolar cell-driven components, then subsequently with additional blockers (see Materials and methods) to isolate the photoreceptor-driven a-wave (red traces). (D) Retinal sensitivity increases at a slower rate (50–60%) between eye opening and adulthood. Population averaged b-wave (top) and a-wave (bottom) amplitudes plotted as a function of flash intensity in P14 (inverted triangle, n = 12 and 16) and adult (diamond, n = 10) retinas. Black fit lines = best fit of Eq. 2. Resultant I1/2 values are listed in Table 1. Error bars = mean ± SEM.
Figure 2.

Rod and cone contributions to the ERG depend on postnatal age. The developmental progression of the mouse ERG. (A) Both WT and Gnat1−/− photoreceptor responses emerge at P8 and increase rapidly in amplitude thereafter. Photoreceptor-driven a-waves at P8, P9, and P10 evoked by green (520 nm) flashes of increasing intensity (delivering 0.19–13,280 photons µm−2) presented at t = 0 (green arrow). Cone responses obtained from Gnat1−/− animals were evoked by the light of increasing intensity (delivering 379–83,835 photons µm−2) without background saturation. The rod-driven nose component emerges at P9 (black arrow) and becomes more robust at P10. Inset: Cone-evoked responses at P10 isolated under the stimulus protocol from Fig. 1. (B) In emergent time points, the dynamic range of the retina is compact at P8. This remains consistent until adulthood. The sensitivity, however, increases by ∼1 log unit with each passing day in development. Population averaged a-wave amplitudes plotted as a function of flash intensity, from P10 (triangle, n = 12), P9 (circle, n = 8), and P8 (square, n = 10) retinas. (C) Outer retinal signaling increases at a slower rate between eye opening and maturity. Response families to the same stimuli used in A from P14 (left) and adult (right) retinas. Insets represent Gnat1−/− a-waves at corresponding time points without background saturation. Retinas were initially perfused with Locke’s media containing BaCl2 to observe both the negative-going photoreceptor component and the positive-going bipolar cell-driven components, then subsequently with additional blockers (see Materials and methods) to isolate the photoreceptor-driven a-wave (red traces). (D) Retinal sensitivity increases at a slower rate (50–60%) between eye opening and adulthood. Population averaged b-wave (top) and a-wave (bottom) amplitudes plotted as a function of flash intensity in P14 (inverted triangle, n = 12 and 16) and adult (diamond, n = 10) retinas. Black fit lines = best fit of Eq. 2. Resultant I1/2 values are listed in Table 1. Error bars = mean ± SEM.

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