Table 3.
Action potential and Nav current parameters in substantia nigra pars reticulata GABA neurons and nigral DA neurons
| Parameters | GABA Neuron | DA Neuron | P |
|---|---|---|---|
| Action potential | |||
| Spontaneous firing rate, Hz | 9.4 ± 0.6 | 1.9 ± 0.2 | <0.01 |
| Spike threshold, mV | −40.3 ± 0.5 | −36.2 ± 0.4 | <0.05 |
| Amplitude, mV | 69.5 ± 1.6 | 59.3 ± 1.4 | <0.01 |
| Base duration, ms | 1.1 ± 0.1 | 2.9 ± 0.2 | <0.01 |
| 10–90% spike rise time, ms | 0.27 ± 0.02 | 0.69 ± 0.05 | <0.01 |
| Average rise rate, mV/ms | 183.8 ± 17.3 | 71.8 ± 8.8 | <0.01 |
| INaT | |||
| Peak INaT density (at −10 mV), pA/pF | 148.9 ± 17.8 | 86.0 ± 14.1 | <0.01 |
| Activation 10–90% rise time (at 0 mV), μs | 85 ± 5 | 84 ± 5 | >0.05 |
| Activation V1/2, mV | −30.2 ± 0.2 | −26.7 ± 0.5 | <0.05 |
| Activation slope K | 6.2 ± 0.2 | 7.3 ± 0.3 | <0.05 |
| Inactivation 10−90% decay time (at 0 mV), μs | 191 ± 12 | 195 ± 15 | >0.05 |
| Steady-state inactivation V1/2, mV | −63.3 ± 1.3 | −61.3 ± 2.5 | >0.05 |
| Steady-state inactivation slope K | 8.1 ± 0.5 | 10.1 ± 1.6 | >0.05 |
| Recovery from inactivation | |||
| τf, ms | 0.59 ± 0.07 | 1.15 ± 0.1 | <0.05 |
| τs, ms | 35.1 ± 6.4 | 79.7 ± 13.1 | <0.05 |
| INaR | |||
| Peak density (at −40 mV), pA/pF | 3.3 ± 0.5 | 1.4 ± 0.6 | <0.01 |
| INaP | |||
| Whole cell peak amplitude (at −40 mV), pA | 185.4 ± 17.5 | 121.3 ± 12.7 | <0.01 |
Values are means ± SE. DA, dopamine projection; INaT, transient voltage-activated sodium current; INaP, persistent Na current; INaR, resurgent Na current; V1/2, the potential at which the value of the Boltzmann function is 0.5; τf, fast recovery; τs, slow recovery. Spike threshold was measured at the point that had the sharpest inflection of membrane potential before the full spike. Base duration starts at the spike threshold point and ends when the membrane potential returns and crosses the spike threshold level.