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. Author manuscript; available in PMC: 2013 Oct 18.
Published in final edited form as: Neuron. 2012 Oct 17;76(2):370–382. doi: 10.1016/j.neuron.2012.07.029

Figure 3. GCAPs-Mediated Feedback Stabilizes the SPR Amplitude against Genetic Perturbations of R* Lifetime.

Figure 3

(A) Family of flash responses from a GCAPs−/− mouse rod showing the determination of the time in saturation (adapted from Gross et al., 2012). Flashes ranged from 4 to 1,800 photons/μm2, corresponding to 1–510 R*/flash in this rod with collecting area of 0.29 μm2.

(B) The time that the response to a bright flash remains in saturation versus the natural log of the number of R* produced by the flash for wild-type (n = 8) Grk1S561L (n = 12), and Grk1+/− (n = 22) rods lacking GCAPs-mediated feedback (GCAPs−/− background), fitted by straight lines with a slope of 200 ms, consistent with the means of τD values measured individually in each rod (Table 1). The vertical displacements (ΔTsat) of the Grk1S561L and Grk1+/− lines from the WT line were −220 ms and +180 ms, respectively, consistent with measurements of τReff in the GCAPs+/+ background (Figure 1B). Error bars reflect S.E.M.

(C) SPRs of rods lacking calcium feedback to cGMP synthesis via GCAPs (GCAPs−/−), but with identical changes in τReff, have substantially larger differences in peak amplitudes than the corresponding responses in the GCAPs+/+ background in Figure 1C.