Table 1.
Parameter values determined from responses recorded by LERG-OS first in normal Ca2+ and then in low Ca2+ from 10 experiments. In 5 experiments, responses were also recorded in normal Ca2+ after the washout of low Ca2+ solution.
| Parameter/Treatment | rmax (µV) | SF,dark (%/R*rod−1) | Φ1/2 (R*rod−1) | τrec (ms) | tp (ms) | tintegr.(ms) | τD (ms) | A (s−2) |
|---|---|---|---|---|---|---|---|---|
| Normal Ca2+ (n = 10) | 45.9 ± 6.3, P = 0.006 | 4.7 ± 0.5, P = 0.003 | 15.6 ± 2.4, P = 0.0008 (n = 9) | 348 ± 20, P = 0.017 | 270 ± 7, P = 0.0004 | 619 ± 35, P = 0.005 | 194 ± 6, P = 0.48 | 19.1 ± 2.3, P = 0.158 |
| Low Ca2+ (n = 10) | 79.3 ± 8.2 | 3.8 ± 0.5 | 18.7 ± 2.5 (n = 9) | 287 ± 15 | 254 ± 7 | 538 ± 24 | 197 ± 6 | 20.3 ± 2.0 |
| Normal Ca2+, wash (n = 5) | 45.5 ± 3.7, P = 0.008 | 4.4 ± 0.6, P = 0.03 | 12.8 ± 2.0, P = 0.056 (n = 4) | 355 ± 24, P = 0.033 | 284 ± 9, P = 0.022 | 670 ± 33, P = 0.068 | 196 ± 7, P = 0.51 | 19.2 ± 3.0, P = 0.159 |
rmax, saturated response amplitude measured from the LERG-OS response plateau level; SF,dark, Fractional sensitivity, dim flash response amplitude divided with the strength of the flash stimulus and saturated response amplitude; Φ1/2, half-saturating flash strength; τrec, time constant of single exponential fit to the recovery phase of dim flash responses; tp, time-to-peak of dim flash response; tintegr, integration time of dim flash response calculated by taking the integral from time of the flash stimulus to the time when the response has completely recovered and dividing the value with the maximal amplitude of the dim flash response; τD, the dominant time constant of saturated response recovery obtained from Pepperberg plot; A, amplification constant determined by fitting the flash response model to the response leading edges (Eq. (15)) of response families from individual experiments, as shown in Fig. 2. The lifetime of light-activated rhodopsin was locked to 28 ms in normal Ca2+ and to 26 ms in a low Ca2+ solution. The statistical significance was tested using two-tailed paired student’s t-test. The parameters derived in normal Ca2+ were first compared to those derived in low Ca2+ and secondly the parameters derived in normal Ca2+ after the washout were compared to low Ca2+ parameters derived in the experiments were the washout was performed. The parameter values are presented as mean ± SEM.