Table 1.

Dark current from single rods

Genotype a (pA) σ (photons μm−2) rmax (pA) tp (msec) ti (msec)
CNGB1+/+ 0.27 ± 0.05 (n = 6) 65.5 ± 11.4 (n = 6) 7.5 ± 0.9 (n = 6) 204 ± 12 (n = 6) 300 ± 22 (n = 6)
CNGB1+/− 0.35 ± 0.05 (n = 5) 58.3 ± 5.6 (n = 5) 8.1 ± 0.8 (n = 5) 203 ± 19 (n = 5) 441 ± 19 (n = 5)
CNGB1−/− 1.3 ± 0.4 (n = 3)
  • All values are mean ± SEM. The number of rods used to determine each parameter is given in parentheses. a, Single-photon response amplitude, calculated from the ensemble variance divided by the ensemble average of 60 identical dim-flash responses; σ, half-saturating flash intensity at 500 nm; rmax, the maximal response amplitude; tp, time-to-peak of dim-flash response; ti, integration time of the dim-flash response, calculated by dividing the time integral of the response by its peak amplitude. For CNGB1−/− rods, only 3 of 35 recorded cells responded to light. Because the maximum responses of these three cells were very small, no detailed analysis of their dim-flash responses was performed.