Firing properties of spiny projection neurons
| Silent | Spontaneously Firing | ||
|---|---|---|---|
| (n = 6) | (n = 17) | ||
| Firing threshold, mVCurrent pulsea | −40.0 ± 3.3 | −43.2 ± 4.7 | NS |
| Cortical stimulationa | −43.8 ± 4.1 | −47.6 ± 4.7 | NS |
| Initial up state | −46.0 ± 6.0 | ||
| Final up state | −45.5 ± 6.0 | ||
| Membrane potential, mVup state averageb (μ2) | −61.6 ± 4.6 | −51.1 ± 7.1 | P < 0.005 |
| up state variance (δ2) | 4.2 ± 1.4 | 3.6 ± 1.4 | NS |
| down state average (μ1) | −73.4 ± 7.1 | −69.2 ± 9.4 | NS |
| down state variance (δ1) | 1.8 ± 0.5 | 3.1 ± 1.1 | NS |
| Ratio (down:up time) (α) | 0.5 ± 0.1 | 0.4 ± 0.1 | NS |
| Rate of rise, mV/msdown to up state | 0.86 ± 0.21 | 0.70 ± 0.19 | NS |
| Membrane resistance,c MΩ | 26.3 ± 10.6 | 23.0 ± 8.2 | NS |
| Action potentialAmplitude (mV) | 56.4 ± 8.4 | 56.8 ± 7.9 | NS |
| Duration (ms)d | 0.8 ± 0.1 | 0.9 ± 0.1 | NS |
| AfterhyperpolarizationAmplitude (mV)e | 9.8 ± 3.1 | 6.7 ± 4.1 | NS |
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Data are means ± SD. NS, not significant. a Firing threshold was significantly more hyperpolarized for action potentials evoked by cortical stimulation than for those evoked by current pulses (P < 0.05, paired t-test). b Average membrane potential in the up state was more depolarized in the spontaneously firing than in the silent spiny neurons (P < 0.005, t-test on time-matched samples of n = 5). c Membrane resistance was determined from membrane potential 40 ms after onset of subthreshold depolarizing current pulses. d Action-potential duration was measured at half maximal amplitude. e AHP amplitude was the difference between threshold potential and minimum value of the AHP.