Table 2.
Biophysical parameters of INa through Nav1.2 channel variants
| Biophysical property | Wild-type | R853Q | L1563V | R1882Q |
| Current density, pA/pF | 240.4 ± 21 | 130.7 ± 19* | 222.7 ± 42 | 402.0 ± 36**** |
| n | 36 | 24 | 14 | 26 |
| Activation | ||||
| V0.5,act, mV | −17.06 ± 0.25 | −18.49 ± 0.31*** | −15.39 ± 0.29*** | −23.08 ± 0.26**** |
| kact, mV | 8.63 ± 0.25 | 8.44 ± 0.28 | 8.19 ± 0.26 | 8.09 ± 0.26 |
| n | 36 | 24 | 14 | 26 |
| Inactivation | ||||
| V0.5,inact, mV | −48.60 ± 0.24 | −55.98 ± 0.69**** | −46.08 ± 0.49*** | −44.23 ± 0.26**** |
| kinact, mV | 7.00 ± 0.21 | 7.45 ± 0.35 | 7.83 ± 0.44 | 7.67 ± 0.24 |
| n | 31 | 21 | 14 | 25 |
| Open probability, Po | ||||
| m × h | 0.012 ± 4e−5 | 0.0078 ± 3e−5**** | 0.016 ± 4e−5**** | 0.036 ± 2e−4**** |
| xc, mV | −38.7 ± 0.1 | −41.0 ± 0.2**** | −30.1 ± 0.1**** | −34.0 ± 0.2**** |
| w1, mV | 14.9 ± 0.1 | 16.9 ± 0.2**** | 16.4 ± 0.1**** | 14.43 ± 0.2 |
| w2, mV | 16.9 ± 0.1 | 18.5 ± 0.2**** | 16.19 ± 0.1* | 14.53 ± 0.2**** |
| Window INa | ||||
| Area, % of total | 1.1 ± 0.06 | 0.91 ± 0.05* | 1.35 ± 0.09* | 2.1 ± 0.14** |
| Persistent INa | ||||
| At −30 mV, % of total | 1.18 ± 0.13 | 1.24 ± 0.14 | 1.23 ± 0.22 | 2.92 ± 0.25**** |
| n | 30 | 21 | 14 | 25 |
| Time course of fast inactivation | ||||
| τf at −30 mV, ms | 2.43 ± 0.20 | 2.23 ± 0.25 | 2.47 ± 0.24 | 3.26 ± 0.22** |
| n | 20 | 14 | 11 | 20 |
| Time course of recovery† | ||||
| τ at −120 mV, ms | 0.90 ± 0.06 | 0.93 ± 0.09 | 0.51 ± 0.07**** | 0.92 ± 0.06 |
| τ at −70 mV, ms | 8.22 ± 0.3 | 8.29 ± 0.5 | 3.47 ± 0.2**** | 8.35 ± 0.5 |
| n | 16 | 14 | 10 | 15 |
| Slow inactivated INa fraction | ||||
| After 195, at −60 mV | 0.23 ± 0.02 | 0.33 ± 0.02** | 0.16 ± 0.02* | 0.21 ± 0.02 |
| After 195, at −50 mV | 0.62 ± 0.02 | 0.71 ± 0.02** | 0.51 ± 0.02*** | 0.61 ± 0.02 |
| n | 12 | 9 | 9 | 8 |
| Time course of slow inactivation | ||||
| τf at −60 mV, ms | 677.5 ± 28 | 310.6 ± 18 | 5,279 ± 480**** | 1,508 ± 144 |
| τf at −50 mV, ms | 777.0 ± 36 | 650 ± 43 | 2,443 ± 207**** | 1,240 ± 111* |
| τs at −60 mV, s | 70.0 ± 11.1 | 78.0 ± 8.4 | 84.4 ± 19.6 | 68.6 ± 6.2 |
| τs at −50 mV, s | 46.6 ± 6.5 | 47.6 ± 7.7 | 52.4 ± 6.5 | 47.2 ± 5.6 |
| n | 12 | 9 | 9 | 8 |
Data are represented as mean ± SEM; h, probability that a channel is not inactivated; k(in)act, slope factor of steady-state (in)activation curve; m, probability that the channel is activated; n, number of cells measured; V0.5,(in)act, membrane potential for half-maximal (in)activation. A represents the peak of the Po curve, xc is the voltage below the peak, w1 and w2 represent width for m and h, respectively. τf and τs, fast and slow time constants, respectively; *P < 0.05, **P < 0.01, ***P < 0.001, or ****P < 0.0001 compared with wild-type, one-way ANOVA with Bonferroni correction.
†
Recovery from fast inactivation.