Physiological variables
| Variable | Description |
|---|---|
| Resting membrane potential (mV) | Stable membrane potential when no current applied |
| Input resistance (MΩ) | Calculated from small hyperpolarizing or depolarizing current steps (≤10 mV deflection) |
| Rheobase (pA) | Threshold current |
| AP1 amplitude (mV) | Amplitude of the first AP |
| AP1 duration (ms) | Time from onset of first AP, calculated as an increase ≥1 mV/100 ms to offset, calculated as return to same voltage as before AP onset |
| AP1 half-width (ms) | Time from half-amplitude during rise to halfamplitude during fall of first AP |
| AP1 rise time (ms) | Time from onset to peak of first AP |
| AP1 fall time (ms) | Time from peak to offset of first AP |
| AP1 rise rate (mV/ms) | AP1 amplitude/AP1 rise time |
| AP1 fall rate (mV/ms) | AP1 amplitude/AP1 fall time |
| AP drop (mV) | AP1 amplitude-AP2 amplitude |
| Spike frequency adaptation | t2/t1, where t1 is the time between the peaks of the first two APs (interspike interval) and t2 is the last interspike interval |
| Frequency (Hz) | Number of APs/0.5 s duration of 2× threshold stimulus |
Action potential properties were measured from the first action potential (AP1) and second action potential (AP2) in response to 500 ms twice threshold current injection. AP2 variables not listed were calculated in the same way as AP1 variables.