Rod photoresponse parameters in WT and GCAP1^−/− mice.

<p>Parameters for both WT and GCAP1^−/− mice average all rods of each type and include “fast” and “slow” rods (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047637#pone-0047637-g005" target="_blank"><b>Figures 5</b></a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047637#pone-0047637-g006" target="_blank"><b>6</b></a> and the <i>Discussion</i> section). Results are given as mean ± SEM (number of cells recorded, P-value from a Student’s t-test for values less than 0.05). The i_0.5 is the flash strength at 500 nm eliciting a half-maximal response, and it varies inversely with sensitivity. SPR amplitude was estimated by dividing the ensemble variance by the mean dim flash response amplitude. Kinetics of the single-photon response were determined from dim flash responses whose amplitude was less than 20% of the maximum. Time to peak was measured from mid-flash to the response peak. Integration time was calculated as the integral of the response divided by response amplitude. Recovery time constant, τ_r, refers to a fit of the final falling phase of the dim flash response with a single exponential. Saturation time constant, τ_c, is the slope of the relation between saturation time and the natural logarithm of the flash strength, by linear regression. R_max is the maximum circulating current recorded from a rod, and fractional amplitude is taken as a ratio of the single-photon-response amplitude to the maximum circulating current from that rod.