Table 1.
Values for kinetic rate constants and voltage-dependencies derived from fitting different models to T-type Ca2+ channel currents
| Parameter | Model Dcontrol | Model DL-cys | Model Fcontrol | Model Facontrol | Burgess model |
|---|---|---|---|---|---|
| NC | 56,901 | 56,901 | 56,901 | 113,802 | 87,000 |
| kC1C2 | 168 ± 30 | 152 ± 23 | 207 ± 30 | 216 ± 30 | 203 |
| kC2C1 | 112 ± 19 | 90 ± 30 | 103 ± 17 | 103 ± 16 | 71 |
| kC2C3 | 2095 ± 167 | 2191 ± 246 | 2353 ± 264 | 2236 ± 334 | 4557 |
| kC3C2 | 396 ± 22∗ | 292 ± 27 | 559 ± 62 | 537 ± 63∗ | 3588 |
| kC3O | 128 ± 6∗ | 229 ± 41 | 92 ± 9∗ | 86 ± 9∗ | 420 |
| kOC3 | 333 ± 12 | 350 ± 13 | 368 ± 13 | 370 ± 13 | 45 |
| kOI | 263 ± 6∗ | 178 ± 16 | 75 ± 28∗ | 64 ± 28∗ | 58 |
| kIO | 2.8 ± 0.6∗ | 1.3 ± 0.2 | 1.9 ± 0.7∗ | 0.8 ± 0.3∗ | 0.08 |
| kC1I1 | 0.0008 | 0.02 | 0.6 | ||
| kI1C1 | 0.02 | 0.02 | 0.2 | ||
| kC2I2 | 46 ± 11∗ | 88 ± 19 | 19 ± 3∗ | 20 ± 3∗ | 3.4 |
| kI2C2 | 0.6 ± 0.2∗ | 2.5 ± 0.9 | 27 ± 5 | 14 ± 3 | 0.7 |
| kC3I3 | 38 ± 7∗ | 41 ± 7∗ | 58 | ||
| kI3C3 | 1.1 ± 0.2 | 0.4 ± 0.1 | 0.08 | ||
| kI2I4 | 14 ± 8 | 5 ± 1 | — | — | — |
| kI4I2 | 3 ± 1∗ | 0.6 ± 0.3 | — | — | — |
| kI1I2 | 207 ± 30 | 216 ± 30 | 4 | ||
| kI2I1 | 5.7 ± 1∗ | 69 ± 8 | 0.9 | ||
| kI2I3 | 2353 ± 264 | 2236 ± 334 | 28 | ||
| kI3I2 | 11± 1 | 11 ± 1 | 0.15 | ||
| kI3I4 | 92 ± 9 | 86 ± 9 | 420 | ||
| kI4I3 | 368 ± 13 | 370 ± 13 | 45 | ||
| Vd fwd | 0.073 ± 0.001∗ | 0.077 ± 0.001 | 0.078 ± 0.001 | 0.077 ± 0.001 | 0.052, 0.055 |
| Vd bkwd | −0.031 ± 0.002∗ | −0.045 ± 0.005 | −0.028 ± 0.003∗ | −0.029 ± 0.003∗ | −0.02, −0.122 |
| Vd kOC3 | −0.015 | −0.015 | −0.015 | −0.015 | −0.028 |
Rate constants are expressed as transitionssec−1. For voltage-dependent transitions, rate constants correspond to −40 mV.
∗ Control value significantly changed by L-cys, in the same direction as shown for Model D, Wilcoxon test. p < 0.05, n = 6. For Models D, F, and Fa, Vd fwd and Vd bkwd refer to the voltage-dependence of forward and backward transitions through the resting states, respectively. For the Burgess model, the two numbers corresponding to each Vd fwd and Vd bkwd represent different values for transitions between C1 and C2 versus C2 and C3. The voltage dependence terms shown for the Burgess model were calculated using data provided in Burgess et al. (11), and are analogous to the voltage-dependence terms used in MAC. The NC parameter represents the average number of available channels calculated for the six DRG cells (see Materials and Methods), except for the Burgess model, where the value shown represents the number of channels resulting in a peak current equal to the average peak current observed for the six DRG cells (−1730 pA), in response to a VC to −35 mV, given the optimized parameters in the Burgess model. For Models D, F, and Fa, the data are expressed as the mean ± SE. Values for the Burgess model are reported in Burgess et al. (11).