Abstract
Cortical GABAergic nonpyramidal cells (NP) regulate activities of cortical pyramidal cells. We investigated morphological dendritic parameters, cross sectional areas of their dendrites, synapse density, in the NPs: basket cell, double bouquet cell, Martinotti cell and so on. The NPs were identified in isolated slices of young rat frontal cortex by whole cell, current-clamp recording, followed by intracellular injection of biocytin. The cells were stained with DAB and embedded in Epon. Many portions of the dendrites from each NP subtype were reconstructed three-dimensionally from serial ultra-thin sections. Each NP dendrites received many excitatory and GABAergic inhibitory synapses. The synaptic densities on their dendrites were almost uniform from proximal to distal dendrites. The dendrite was simply recognized as a pillar of a true circle by most scientists. However the identified NP dendrites were not a right pillar but an ellipse pillar. The distortion rate: a cross sectional area of a reconstructed dendrite which section was ellipse / an area of a right circle with the circumferential length of the reconstructed dendrite, is 0.2–0.9 and they were distorted more in thicker dendrites. The dendritic cross sectional area proximal to a branching point is almost equal to sum of cross sectional area of two daughter branches. Dendritic diameters could not be defined correctly under light microscope due to the distortion, but input conductance estimation using the circumference and cross sectional areas suggested impedance matching between parent and daughter branches at the node according to Rall's idea. [Jpn J Physiol 55 Suppl:S14 (2005)]
