Table 1.
Summary of the kinetic features of cation channels observed in single channel patches before and after application of ATP
| Condition | n | Po | τo1 (%) | τo2 (%) | τc1 (%)* | τc2 (%)† | τc3 (%) |
|---|---|---|---|---|---|---|---|
| Control | 5 | 0.07 ± 0.02 | 1.02 ± 0.20 (43) | 9.1 ± 1.5 (57) | 0.46 ± 0.13 (42) | 3.8 ± 1.2 (15) | 384 ± 130 (44) |
| ATP | 5 | 0.40 ± 0.11 | 1.37 ± 0.37 (43) | 22.7 ± 8.5 (57) | 0.58 ± 0.22 (51) | 3.3 ± 1.5 (19) | 69 ± 23 (25) |
All τ values are expressed in milliseconds. Means are presented ± SEM. The percentage of events described by each exponential is given in parentheses. The single channel patches used for kinetic analysis were chosen on the basis of noise levels and the duration of recording; the average Po for all single channel patches of the present study (n = 14) was 0.04 ± 0.01 (control) and 0.25 ± 0.08 (in ATP). The concentration of ATP used in the five patches was, in mM, 0.5, 0.5, 1, 2, and 3.
The briefest closures are poorly resolved at the employed filter frequency leading to an overestimation of τc1, and potentially obscuring any differences between the two conditions in gating events on the microsecond timescale.
A somewhat improved fit was obtained if the closed durations described by τc2 (corresponding to the trough between the two major peaks) were fit with two exponentials instead of one. Variability in the τc2 column may be due to the conservative fit chosen.