Table 1Firing and electrical membrane characteristics of substantia nigra neurons
| SNr GABA n=5 | SNr dopamine n=17 | SNc dopamine n=11 |
| Firing – frequency (Hz) | 7.4±3.7*† | 2.3±1.0 | 1.6±0.9 |
| Firing – range (Hz) | 0–19.7 | 0–12.4 | 0–7.1 |
| Input resistance (MΩ) | 85.8±18.3 | 80.4±8.1 | 110.5±10.0 |
| AP threshold (mV)‡ | −51.8±5.2 | −38.9±2.7 | −38.7±1.7 |
| AP amplitude (mV)§ | 61.6±3.1 | 52.1±1.7 | 55.2±3.1 |
| AP halfwidth (ms)|| | 0.45±0.03**†† | 1.49±0.10 | 1.45±0.11 |
| AHP amplitude (mV)§ | 14.6±1.7*† | 24.1±1.6 | 22.1±2.5 |
| AHP time (ms)¶ | 1.5±0.15**†† | 9.4±1.0 | 8.2±1.0 |
| Coefficient of variation | 0.40±0.11 | 0.61±0.13 | 0.65±0.19 |
| Neurons expressing IA | 0/5 | 17/17 | 11/11 |
| Neurons expressing Ih | 0/5 | 17/17 | 11/11 |
| Neurons expressing LTS or PLSD | 0/5 | 12/17 | 7/11 |
Data are given as mean±S.E.M. AP, action potential; AHP, afterhyperpolarization; IA, A-like transient outward rectification; Ih, anomalous inward rectification; LTS, low-threshold calcium spike; PLSD, pacemaker-like slow depolarization.*P<0.05, **P<0.01 – significantly different from SNc dopamine neurons.†P<0.05, ††P<0.01 – significantly different from SNr dopamine neurons.‡AP threshold taken as the point where the rate of rise is 5% of the maximum.§Measured from threshold of AP to peak.||Duration of the AP measured half way between threshold and peak.¶Time of the peak of the AHP, measured from the peak of the AP.
