TABLE 1.Excitability and timing parameters in +/+control and Ik1 reduced MNTB cells
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Parameter | +/+ACSF | Kcna1–/– | 3 nM DTX-K | 100 nM DTX-K |
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Input resistance (Rin), MΩ | 203 ± 35 (10) | 211 ± 21 (10) | 205 ± 22 (11) | 233 ± 22 (11)‡3 |
Threshold current (Ith), nA | 0.88 ± 0.09 (7) | 0.62 ± 0.05* (12) | 0.62 ± 0.04* (19) | 0.31 ± 0.05† (8) |
Latency at Ith, ms | 1.23 ± 0.03 | 1.48 ± 0.13* | 1.38 ± 0.08* | 8.64 ± 2.1† |
Jitter at Ith, ms | 0.07 ± 0.02 | 0.16 ± 0.03† | 0.22 ± 0.05† | 2.6 ± 0.62† |
Spike threshold(Vth), mV | 21.1 ± 1.3 | 16.1 ± 1.6* | 15.1 ± 1.2† | 8.7 ± 1.4† |
Maximum AP slope, mV/ms | 264 ± 35 | 340 ± 17 | 365 ± 25* | 354 ± 28 |
Values are means ± SE. Input resistance calculated from the current response to voltage steps from –60 to –65 mV (protocol
from Fig. 1A, number of cells in parentheses). Other measurements use the current clamp protocol in Fig. 3A. Threshold current
(Ith) was the minimum current to generate at least 3 APs, except for 100 nM DTX-K–treated cells, where we used the smallest current
to generate at least 1 AP with no temporal summation and at least 3 APs total (number of cells in parentheses applies to Ith and subsequent measurements). Latency at Ith was the mean time from stimulus onset to AP peak in response to Ith. Jitter at Ith was the SD of the latencies at Ith. AP threshold (Vth) was the mean peak depolarization of AP failures in response to the largest current to evoke ≤7 APs. Maximum AP slope is
the maximum rise over 3 data points for APs in response to the current intensity that resulted
in AP latency 0.9 ± 0.1 which yielded the fastest rise for APs after the stimulating current ended. Compared with +/+,
* P < 0.05.
† P < 0.01, unpaired Student's t-test. Compared to +/+ and 3 nM DTX-K–treated cells,
‡ P < 0.01, paired Student's t-test. MNTB, medial nucleus of the trapezoid body; ACSF, artificial cerebrospinal fluid; DTX-K, dendrotoxin-K; AP, action potential.