Table 1.

Light (flash) response parameters from WT, Gcaps^−/−, Gcap1^−/−, and Gcap2^−/− mouse cones

All recordings were from Gnat1^+/+ mice except for the light adaptation parameters I₀ and n, which were obtained from Gnat1^−/− mice. Retinas were exposed to constant 70,000 photons (530 nm) μm⁻² s⁻¹ background light to suppress the rod component of the response except in the light adaptation experiments that were from Gnat1^−/−mice. r_max, saturated photoresponse amplitude (I_F = 183,000 photons μm⁻² at 530 nm); t_p, time to peak (I_F = 220 photons μm⁻² at 530 nm); t_i, integration time defined as an area under a dim flash response divided by the amplitude of the response; I½, light flash intensity eliciting a response with peak amplitude r = 0.5r_max determined by fitting Equation 1 to the response amplitude data; I₀, background light intensity at which cone sensitivity is 50% of that in darkness determined by fitting Equation 2 to the light adaptation data; n, steepness factor determined by fitting Equation 2 to the light adaptation data. * and † indicate statistically significant difference as compared with the WT control and Gcaps^−/− mouse cones, respectively (p < 0.05, two-tailed Student's t test). NA, not available.

Genotype	rmax	tp	ti	I½	I0	n
	μV	ms	ms	photons μm−2	photons μm−2
WT	144 ± 15	53 ± 1	51 ± 0.1	3,200 ± 130	14,500 ± 3,000	1.0 ± 0.1
GCAPs−/−	156 ± 26	76 ± 3*	90 ± 9*	1,900 ± 150*	3,600 ± 800*	1.5 ± 0.03*
GCAP1−/−	135 ± 6	66 ± 3*	64 ± 4*†	2,100 ± 320*	6,900 ± 900*	1.0 ± 0.02†
GCAP2−/−	125 ± 18	52 ± 2†	49 ± 2†	4,000 ± 450†	NA	NA