Morphological subtypes in L6 differ only marginally in electrophysiological properties
Tall L6 | Wide L6 | Short L6 | Small L6 | P | |
---|---|---|---|---|---|
Morphology | N = 5 | N = 3 | N = 5 | N = 5 | |
Location in L6 (%) | 31% ± 6% | 13% ± 8% | 49% ± 17% | 30% ± 9% | 0.28 |
Field span apical dendrites (μm) | 295 ± 27 | 201 ± 63 | 361 ± 127 | 147 ± 10 | 0.22 |
Field span basal dendrites (μm) | 215 ± 8 | 751 ± 184** | 300 ± 10 | 181 ± 8 | <0.01 |
Total length apical dendrites (μm) | 3853 ± 371* | 1930 ± 329 | 2470 ± 533 | 1083 ± 144 | <0.01 |
Total length basal dendrites (μm) | 1685 ± 250 | 3387 ± 487* | 2464 ± 187* | 1597 ± 131 | <0.01 |
Soma (μm2) | 186 ± 20 | 189 ± 24 | 218 ± 24 | 185 ± 9 | 0.57 |
Number of apical branches | 25.2 ± 2.5* | 9.0 ± 3.6 | 15.0 ± 4.5 | 13.6 ± 2.1 | 0.03* |
Number of basal branches | 19.6 ± 2.8 | 17.3 ± 3.8 | 21.2 ± 3.6 | 18.0 ± 3.1 | 0.85 |
Vertical span (ending layer) | 5 × L1 | 2 × L1 1 × L3 |
2 × L3 1 × L5 2 × L6 |
4 × L5 1 × L6 |
<0.01 |
Electrophysiology | N = 4 | N = 3 | N = 4 | N = 2 | |
Ratio ISI-1/ISI-9 | 0.49 ± 0.05 | 0.35 ± 0.14 | 0.42 ± 0.12 | 1.06 ± 0.42 | 0.53 |
Ratio ISI-2/ISI-9 | 0.79 ± 0.07 | 0.58 ± 0.15 | 0.66 ± 0.19 | 1.28 ± 0.39 | 0.27 |
Ratio ISI-3/ISI-9 | 0.93 ± 0.03 | 0.88 ± 0.06 | 1.12 ± 0.14 | 1.35 ± 0.20 | 0.08 |
Increase in firing frequency (Hz/100 pA) | 15.6 ± 1.5 | 12.2 ± 1.8 | 11.6 ± 1.8 | 24.8 ± 1.3 | 0.64 |
Membrane potential (mV) | -68.1 ± 1.9 | -66.8 ± 0.8 | -75.2 ± 2.9 | -76.1 ± 1.3 | 0.01* |
Input resistance (MΩ) | 276 ± 47 | 354 ± 85 | 236 ± 18 | 433 ± 40 | 0.67 |
Rheobase (pA) | 78 ± 22 | 60 ± 10 | 125 ± 23 | 65 ± 5 | 0.32 |
Time constant (ms) | 29.7 ± 4.0 | 33.1 ± 1.7 | 21.4 ± 4.7 | 21.8 ± 5.5 | 0.09 |
Voltage sag (%) | 10.3 ± 2.5 | 13.1 ± 3.9 | 4.4 ± 2.9 | 6.9 ± 1.4 | 0.11 |
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Note: For clarity, the results of the post hoc comparison of groups is only given (values in bold followed with asterisks) when a cell type is different from all other cell types. *P < 0.05, **P < 0.01. Note that, for vertical span, the χ2 test was used. In the comparison of electrophysiological properties, “short” and “small” L6 pyramidal neurons were grouped to increase the number of observations. Short and small L6 pyramidal neurons are 2 subdivisions of the third cluster of the CA.