TABLE I. Light response parameters of WT and Palm−/−.
Values given as mean ± S.E. (n). The current circulating in darkness was given by the amplitude of the response to a saturating flash. Single photon response amplitude was estimated by dividing the ensemble variance by the mean response amplitude. Kinetics were determined from dim flash responses whose amplitudes were a fifth 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. i½ and I½ are the light strengths giving rise to half-maximal flash and step responses, respectively. Comparisons were made using a t test. ns, not significant.
| WT | Palm−/− | p | |
|---|---|---|---|
| Circulating current, pA | 8.8 ± 0.3 (59) | 8.8 ± 0.2 (95) | ns |
| Single photon response | |||
| Amplitude, pA | 0.53 ± 0.08 (5) | 0.43 ± 0.04 (10) | ns |
| Time to peak, ms | 128 ± 3 (43) | 128 ± 3 (75) | ns |
| Integration time, ms | 335 ± 17 (43) | 252 ± 9 (75) | <0.0001 |
| Sensitivity to flashes, i½, photons µm−2 | 46 ± 2 (58) | 52 ± 2 (95) | <0.01 |
| Sensitivity to steps, I½, photons µm−2 s−1 | 120 ± 11 (8) | 238 ± 30 (14) | <0.01 |