Neurons receive thousands of synaptic inputs onto their dendrites and soma, and integrate these inputs spatially and temporally to produce appropriate output in the form of action potentials generated in axons. Dendritic trees influence synaptic integration and neuronal excitability. Previously we found conserved dimensional properties of dendritic trees in four cortical non-pyramidal cell subtypes. First, the cross-sectional area at any given point within a dendrite is proportional to the summed length of distally located dendrites beyond it, including all subsequent dendritic branches. Second, the total cross-sectional area is conserved at dendritic bifurcation points. Third, dendritic cross-sections became progressively more elliptical at more proximal, larger diameter, dendritic locations. We investigated whether the similar morphological properties could be found in pyramidal cell. Using three-dimensional reconstructions from light and electron microscopic observations, we analyzed the dendritic trees of crossed-corticostriatal (CCS) "slender untufted" cortical pyramidal cells in layer V, which was stained with DAB after whole cell recording using slice preparation. Our ultrastructural data revealed the similar conserved principles governing the dendritic dimensions of the pyramidal cell. The conservation of cross-sectional area at bifurcation point of the dendrite was also found in non-stained bifurcated dendrites of pyramidal cells in all layers using serial block face scanning electron microscopy, so we believe it is a general morphological principle of the dendritic tree. These conserved morphological features limit distance dependent filtering of somatic EPSPs and facilitate distribution of somatic depolarization into all dendritic compartments, as we showed in the non-pyramidal cells previously.
Reference: Scientific Reports, 1, 89, 2011