Figure 3

The cross-sections of nonpyramidal cell dendrites are irregular ellipses.

(a) Ellipticity Index plotted against cross-sectional area for dendritic segments in each of the four neurons studied. Ellipticity indices were generally between 0.4 and 0.9 in most dendrites. Proximal (thicker) dendrites tended to be flatter than distal (thinner) dendrites. The index of a circle is 1 and that of a line is 0. (b) Reconstructed image of a dendrite segment of the Martinotti cell. The cross-section is an ellipse. (c) Average ellipticity index of the FS cell is smaller than those of the double bouquet cell (*Tukey, p = 0.029). MA, Martinotti cell; FS, FS basket cell; DB, double bouquet cell; LB, large basket cell. (d) Rotating 3D image of the elliptical dendritic segment of the large basket cell. The apparent thickness varies greatly when viewed from different angles (arrows) and pronounced diameter fluctuations are apparent along the segment length when viewed from a single point of view, as would occur under light microscopy. (e) Cross-sectional areas plotted against perimeter of the cross-section showing a strong linear correlation between the two variables. Line of true circle (red doted curve) and liner fit line are shown. The larger dendrites are located below the curve of true circle, although the smaller dendrites are tend to be on or quite near the curve. It suggested the smaller dendrites tended to be true circle, but the larger ones were rather elliptical in their cross section. (f) Surface-area-to-volume ratios plotted against distance from soma showing constant especially from 30 – 40 µm from soma or more distal. (g–i) Ultrastructure of Martinotti cell dendrites shown as p, m, d in dendrogram of Figure 1b . Note that the proximal dendrite (g) contains many organelles, while the middle (h) and distal dendrites (i) contain only a small number of organelles. Scale bar, 1 µm.