Table 2.
Inactivation and recovery kinetic parameters
| Subunit | Inactivation
timecourse*
|
Recovery from
inactivation*
|
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Percentage in fast mode | Percentage in fast mode | Voltage-dependence of
inactivation†
|
|||||||||
| τ1, ms | τ2, ms | n | τ1, ms | τ2, ms | n | V1/2, mV | k, mV | n | |||
| αIIA | 2.4 ± 0.3 | 10.9 ± 1.3 | 46 ± 4 | 8 | 3.9 ± 0.2 | 446 ± 9 | 38 ± 0.4 | 5 | −45.1 ± 0.3 | 9.8 ± 0.2 | 4 |
| αIIA + β1 | 1.4 ± 0.2 | 24.7 ± 4.3 | 95 ± 1 | 5 | 2.0 ± 0.1 | 148 ± 19 | 84 ± 0.4 | 5 | −49.1 ± 0.3 | 5.9 ± 0.2 | 4 |
| αIIA + β3 | 1.5 ± 0.2 | 24.7 ± 4.3 | 85 ± 1 | 6 | 4.1 ± 0.2 | 170 ± 17 | 73 ± 1.2 | 5 | −49.3 ± 0.2 | 6.1 ± 0.1 | 4 |
Analysis of inactivation and recovery kinetics of rat αIIA separately coexpressed with β1- and β3-subunits. The inactivation and recovery from inactivation time constants for different combinations of rat αIIA, rat β1, and rat β3 subunits are shown above separately calculated from data shown in Fig 4. Percentage in fast mode is the proportion of current described by the fast exponential time constant. This percentage is calculated by the equation A1/(A1 + A2), where A1 and A2 are the amplitudes of the fast and slow exponential components, respectively. V1/2 is the voltage of half-maximal inactivation, and k is the slope factor.
There was a significant difference between the proportion of channels described by the fast gating mode for αIIA expressed alone compared to αIIA coexpressed with either β1 or β3 (P < 0.001) and between αIIA coexpressed with β1 compared to β3 (P < 0.001) as determined by Student's t test.
† There was a significant difference in V1/2 and k for αIIA alone compared to αIIA expressed with either β1 or β3 (P < 0.005) as determined by Student's t test. Differences between V1/2 and k for αIIA coexpressed with β1 compared to β3 were not statistically significant.