Table 1. Characteristics of WT, GCAP −/−...

Table 1.

Characteristics of WT, GCAP^−/− and DKO mouse rods

Parameter	Solution	WT (n = 4)	GCAP^−/− (n = 9)	GCAP^−/− Rv^+/+ (n = 4)	DKO (n = 3)
r_max (µV)	1 mM Ca²⁺	379 ± 98	165 ± 20	145 ± 27 (n = 7)	156 ± 8
	Low Ca²⁺	556 ± 145	171 ± 23	154 ± 14 (n = 7)	170 ± 12
S_F,D (% R*⁻¹)	1 mM Ca²⁺	1.7 ± 0.6^a	4.5 ± 0.6^a	4.4 ± 0.7^a^,^b	2.8 ± 0.03^a^,^b
	Low Ca²⁺	0.3 ± 0.2^a	1.0 ± 0.2^a	1.4 ± 0.4^a	1.5 ± 0.2^a
t_p (ms)	1 mM Ca²⁺	156 ± 1^a	366 ± 9^a	369 ± 20^a^,^c	233 ± 7^c
	Low Ca²⁺	450 ± 40^a	267 ± 8^a	262 ± 19^a	231 ± 5
I₀ (R*)	1 mM Ca²⁺	181 ± 46/165 ± 43	28 ± 6^a/39 ± 9^a	34 ± 9^a/46 ± 11^a^,^b	65 ± 2^d/68 ± 4^b^,^d
	Low Ca²⁺	NA	183 ± 46^a/215 ± 54^a	131 ± 31^a/187 ± 56^a	153 ± 20^d/167 ± 33^d
n	1 mM Ca²⁺	1.0 ± 0.1/1.1 ± 0.1	1.1 ± 0.05^d/1.5 ± 0.1^d	1.1 ± 0.08^d/1.6 ± 0.15^d	1.5 ± 0.03/1.7 ± 0.1^d
	Low Ca²⁺	NA	1.5 ± 0.1^d/2.1 ± 0.2^d	1.4 ± 0.01^d/2.0 ± 0.2^d	1.8 ± 0.3/2.0 ± 0.04^d
τ_D	1 mM Ca²⁺	178 ± 21^a	231 ± 16 (n = 4)	261 ± 19^a (n = 7)	200 ± 21
ms	Low Ca²⁺	464 ± 54^a	191 ± 20 (n = 4)	204 ± 11^a (n = 7)	200 ± 4
A	1 mM Ca²⁺	4.7 ± 1.2^a	7.9 ± 1.3 (n = 6)	7.2 ± 1.4 (n = 7)	11.3 ± 1
s⁻²	Low Ca²⁺	0.3 ± 0.1^a	6.2 ± 1.5 (n = 6)	6.6 ± 1.3 (n = 7)	9.8 ± 1

Parameter	Solution	WT (n = 4)	GCAP^−/− (n = 9)	GCAP^−/− Rv^+/+ (n = 4)	DKO (n = 3)
r_max (µV)	1 mM Ca²⁺	379 ± 98	165 ± 20	145 ± 27 (n = 7)	156 ± 8
	Low Ca²⁺	556 ± 145	171 ± 23	154 ± 14 (n = 7)	170 ± 12
S_F,D (% R*⁻¹)	1 mM Ca²⁺	1.7 ± 0.6^a	4.5 ± 0.6^a	4.4 ± 0.7^a^,^b	2.8 ± 0.03^a^,^b
	Low Ca²⁺	0.3 ± 0.2^a	1.0 ± 0.2^a	1.4 ± 0.4^a	1.5 ± 0.2^a
t_p (ms)	1 mM Ca²⁺	156 ± 1^a	366 ± 9^a	369 ± 20^a^,^c	233 ± 7^c
	Low Ca²⁺	450 ± 40^a	267 ± 8^a	262 ± 19^a	231 ± 5
I₀ (R*)	1 mM Ca²⁺	181 ± 46/165 ± 43	28 ± 6^a/39 ± 9^a	34 ± 9^a/46 ± 11^a^,^b	65 ± 2^d/68 ± 4^b^,^d
	Low Ca²⁺	NA	183 ± 46^a/215 ± 54^a	131 ± 31^a/187 ± 56^a	153 ± 20^d/167 ± 33^d
n	1 mM Ca²⁺	1.0 ± 0.1/1.1 ± 0.1	1.1 ± 0.05^d/1.5 ± 0.1^d	1.1 ± 0.08^d/1.6 ± 0.15^d	1.5 ± 0.03/1.7 ± 0.1^d
	Low Ca²⁺	NA	1.5 ± 0.1^d/2.1 ± 0.2^d	1.4 ± 0.01^d/2.0 ± 0.2^d	1.8 ± 0.3/2.0 ± 0.04^d
τ_D	1 mM Ca²⁺	178 ± 21^a	231 ± 16 (n = 4)	261 ± 19^a (n = 7)	200 ± 21
ms	Low Ca²⁺	464 ± 54^a	191 ± 20 (n = 4)	204 ± 11^a (n = 7)	200 ± 4
A	1 mM Ca²⁺	4.7 ± 1.2^a	7.9 ± 1.3 (n = 6)	7.2 ± 1.4 (n = 7)	11.3 ± 1
s⁻²	Low Ca²⁺	0.3 ± 0.1^a	6.2 ± 1.5 (n = 6)	6.6 ± 1.3 (n = 7)	9.8 ± 1

The GCAP^−/− mice were divided into two groups: the GCAP^−/− mice representing the original knockout strain, and the GCAP^−/− Rv^+/+ mice derived by crossing the GCAP^−/− and Rv^−/− strains. The latter were littermates to the DKO GCAP^−/− Rv^−/− mice. Parameter values for rods lacking GCAPs are given both in normal and low (∼20 nM) [Ca²⁺]. Parameters: r_sat, saturated maximal rod response amplitude; S_F,D, fractional dark-adapted sensitivity of rods to dim flashes, i.e., dim-flash response amplitude divided by r_sat and flash strength in R*; t_p, time from flash to the peak amplitude of a dim-flash response; I₀ in R* s⁻¹ per rod, sensitivity-halving background light intensity (see Eq. 1; values are given from fittings to linear/logarithmic data); n, slope of the modified Weber–Fechner function (see Eq. 1; values are given from fittings to linear/logarithmic data); τ_D, dominant time constant of saturated photoresponse recovery; A, amplification constant (Lamb and Pugh, 1992). Values are mean ± SEM, and the number of mice for each genotype is given in parentheses.

P < 0.005, paired Student’s t test is used to indicate statistical significance of low Ca²⁺ exposure in GCAP^−/− and DKO mice.

P < 0.05, one-tailed Student’s t test is used to compare whether parameters between GCAP^−/− Rv^+/+ and DKO littermate mouse rods are different.

P = 0.003, one-tailed Student’s t test is used to compare whether parameters between GCAP^−/− Rv^+/+ and DKO littermate mouse rods are different.

P < 0.05, paired Student’s t test is used to indicate statistical significance of low Ca²⁺ exposure in GCAP^−/− and DKO mice.

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