Figure 5.

Population average single-photon responses reveal decrease in amplification in Gα_tG2A/Gα_t^−/− rods. A, Un-normalized average single-photon response from 11 Gα_tG2A/Gα_t^−/− rods (bottom trace) and 10 wild-type rods (top trace). The average dark current for the wild-type rods was 10.3 pA, and that for the Gα_tG2A rods was 16.6 pA. B, Same responses as in A, on an expanded time scale. Error bars indicate SEM. C, Same responses as in A, on a further expanded time scale. The dotted curves are the best parabolic fits of Equation 23 of Pugh and Lamb (1993) (see Results, Physiology of Gα_tG2A rods, Eq. 2), yielding amplification constants of 12.4 s⁻² for the average wild-type response and 4.1 s⁻² for the average Gα_tG2A/Gα_t^−/− response.