Summary of the voltage-dependent properties of cloned calcium channels
| Activation | Inactivation | |||||
|---|---|---|---|---|---|---|
| V50 | k | τact | V50 | k | τin | |
| α1I | −24.7 ± 0.2 | 8.1 ± 0.2 | 4.7 ± 0.3 | −68.3 ± 0.8 | −6.3 ± 0.7 | 55 ± 3 |
| α1G | −28.6 ± 0.9 | 8.9 ± 0.8 | 1.8 ± 0.1 | −72.4 ± 0.5 | −4.8 ± 0.5 | 15 ± 1 |
| α1H | −31.4 ± 0.9 | 8.8 ± 0.8 | 1.7 ± 0.2 | −80.9 ± 0.4 | −5.5 ± 0.4 | 14 ± 1 |
| α1Eβ3 | −10.9 ± 0.5 | 6.3 ± 0.4 | 1.3 ± 0.1 | −75.5 ± 0.5 | −7.3 ± 0.5 | 48 ± 2 |
| α1I-2 Ca | −45.0 ± 0.9 | 7.6 ± 0.8 | 3.9 ± 0.3 | −77.1 ± 0.6 | −6.0 ± 0.5 | 76 ± 10 |
Average data were fit with the Boltzmann equation to determine the midpoint of voltage dependence (V50, mV) and slope (k). Time constants (in milliseconds) of activation and inactivation were calculated from double exponential fits to the current traces obtained during test pulses to +10 mV.