A, Mean responses averaged from 18 ILE86TER rods to responses of 20 ms flashes of the following intensities (in photons µm2): 17, 43, 159, 453, and 1120. Same traces as in Fig. 4B. B, Mean responses averaged from 9 ILE86TER rods in presence of 100 µM IBMX to responses of 20 ms flashes of same intensities as in A. C, Mean responses averaged from 14 ILE86TER/GCAP−/− rods to responses of 20 ms flashes of same intensities as in A and B. D, Mean responses averaged from 11 ILE86TER/GCAP−/− rods in presence of 100 µM IBMX to responses of 20 ms flashes of the following intensities (in photons µm2): 17, 43, 159, 453, and 646.