Figure 5.
Distance-dependent subthreshold membrane properties of layer 5 dendrites. A, Dendritic recordings at RMP were obtained at various distances from the soma in L5 neurons. We observed two classes of L5 dendrites: those with membrane properties consistent with CPn neurons at the soma (CPn-type) and those with membrane properties consistent with COM neurons at the soma (COM-type). B, In CPn-type dendrites, RN and rebound slope decreased with distance from the soma (both p < 0.001, Pearson's product moment correlation). Conversely, in COM-type dendrites, these measurements were distance independent (both p = 0.18, Pearson's product moment correlation). Sample voltage sweeps from which RN and rebound were calculated are shown at left. C, Resonance increased with distance from the soma in CPn-type dendrites (p < 0.001, Pearson's product moment correlation), whereas resonance was ∼1 Hz in COM-type dendrites at all distances sampled (p = 0.10, Pearson's product moment correlation). Sample voltage sweeps and ZAPs in response to a chirp stimulus for each cell type are shown at left. Average values for RN, rebound, and resonance from somatic recordings in 12 COM neurons and 13 CPn neurons are also plotted for comparison. Dotted lines represent linear regression fits. R2 values are reported in the text. Arrows indicate the sample recordings. Red data points denote instances where Lumafluor beads could be clearly identified at the soma. The presence of Alexa-594 in the recording pipette rendered this difficult.