Action potential characteristics of small-diameter (≤26 μm) IB4-positive and -negative dorsal root ganglion neurons
| Soma diameter (μm) | Cell capacitance (pF) | Input resistance (mOhm) | Membrane potential (mV) | AP threshold (pA) | AP height (mV) | AP 50% width (msec) | AP 75% width (msec) | n | |
|---|---|---|---|---|---|---|---|---|---|
| IB4negative, with inflection | 21.8 ± 0.6 | 16.5 ± 1.1 | 437.3 ± 52.8 | −52.1 ± 2.4 | 209.3 ± 32.9* | 97.9 ± 4.7 | 6.11 ± 0.5** | 3.18 ± 0.3** | 29 |
| IB4 positive, with inflection | 22.2 ± 0.4 | 18.4 ± 0.8 | 344.6 ± 49.9 | −51.7 ± 1.4 | 299.5 ± 36.7 | 102.67 ± 2.93 | 9.56 ± 0.94 | 5.45 ± 0.53 | 39 |
| IB4 negative, no inflection | 23.6 ± 1.2 | 21.6 ± 3.0 | 333.5 ± 67.3 | −51.4 ± 2.1 | 306.7 ± 56.3 | 88.40 ± 5.04 | 5.63 ± 0.87 | 2.80 ± 0.51 | 12 |
| IB4 positive, no inflection | 22.8 ± 0.5 | 19.4 ± 3.1 | 340.8 ± 113.2 | −51.7 ± 3.7 | 176.7 ± 49.1 | 99.4 ± 11.1 | 8.82 ± 1.76 | 3.82 ± 0.46 | 6 |
Asterisks indicate IB4-negative group with action potential inflection is significantly different from IB4-positive group with inflection (**p < 0.05, two-tailed t test; *p < 0.05, one-tailed t test). The mean diameter of neurons analyzed electrophysiologically was somewhat larger than the mean diameter of neurons (≤26 μm) analyzed in the fixed cultures. This difference is likely attributable to systematic differences in the methods for analyzing the cell diameters on two different microscopes (see Materials and Methods) and to shrinkage of neurons that can occur with fixation.