Table 1.
Biophysical heterogeneity across the tonotopic axis in NM.
| Properties | NMc (n) | M to HF NMa | P, t-test |
|---|---|---|---|
| KV current properties | |||
| Current at +20 mV (nA) | 2.83 ± 0.90 (35) | 6.24 ± 1.33 (39) | P <0.0001 |
| Current density at +20 mV (nA/pF) | 0.10 ± 0.65 (25)∗ | 0.26 ± 0.66 (15)∗ | P <0.0001 |
| Conductance at +20 mV (nS) | 24.79 ± 7.90 (35) | 54.74 ± 11.64 (39) | P < 0.0001 |
| KV1 mediated current at +20 mVb | ∼25% | ∼49% | |
| KV2 mediated current at +20 mVb | ∼30% | Minimalc | |
| KV3 mediated current at +20 mVb | ∼40% | ∼51% | |
| Transient NaV current properties | |||
| Max rise rate (nA/ms) | –16.83 ± 9.18 (14) | –10.55 ± 5.74 (11) | P = 0.059 |
| Max fall rate (nA/ms) | 4.24 ± 1.69 (14) | 2.78 ± 1.12 (11) | P = 0.022 |
| Half width (ms) | 1.14 ± 0.24 (14) | 1.13 ± 0.14 (11) | P = 0.934 |
| Reliability range (ms) | 0.11 ± 0.12 (13) | 0.50 ± 0.42 (18) | P = 0.003 |
| Current at -30 mV (nA) | –5.75 ± 2.68 (31) | –2.94 ± 0.88 (11) | P = 0.002 |
| Current density at -30 mV (nA/pF) | –0.08 ± 0.03 (15) | –0.09 ± 0.05 (10) | P = 0.687 |
| Conductance at -30 mV (nS) | 73.11 ± 30.57 (31) | 54.70 ± 13.59 (11) | P = 0.011 |
| Inactivation V1/2 (mV) | –48.42 ± 4.30 (12) | –54.67 ± 3.77 (7) | P = 0.002 |
| Slope factor k (mV) | 3.75 ± 0.64 (12) | 4.55 ± 0.70 (6) | P = 0.027 |
| Resurgent NaV current properties | |||
| Max current (nA) | –0.49 ± 0.21 (13) | –0.81 ± 0.21 (17) | P = 0.0003 |
| Time to peak (ms)d | 6.65 ± 1.83 (12) | 4.28 ± 0.70 (17) | P < 0.0001 |
| Decay time constant (ms)d | 17.82 ± 2.65 (12) | 24.92 ± 6.71 (17) | P = 0.002 |
| Persistent NaV current properties | |||
| Current at -30 mV (nA)e | –0.10 ± 0.03 (12) | –0.14 ± 0.05 (16) | P = 0.019 |
aData of mid- to high-frequency NM neurons are taken from Hong et al. (2016) for KV and transient NaV current properties, and Hong et al. (2017) for resurgent and persistent NaV current properties. M, mid, HF = high-frequency.
bPercent relative to the total KV current.
cFrom Kuba et al. (2015) and Hong et al. (2016).
dTime to peak and decay time constant were calculated at the repolarizing membrane voltage of -30 mV for both neuronal groups. The conditioning step is +30 mV for 10 ms.
ePersistent current amplitude was measured at the end of 100 ms repolarizing membrane voltage at -30 mV for both neuronal groups. The conditioning step is +30 mV for 10 ms.
∗Non-parametric Mann–Whitney U test was used to compare current density at +20 mV.