Figure 6. Maturation of parasympathetic postganglionic arbors in the submandibular gland mostly during the first postnatal week.
(A) A single P1 ganglion cell with small dendritic branches and a large diffusely branched axon that possessed no basket endings (from Thy1 YFP-H line). Orange box is a magnified view of one portion of the arbor (B) A single P7 ganglion cell with no dendritic branches and an axon that has an organization similar to arbors in adult animals with basket terminals (orange arrows and box; inset shows magnified view of the box). As in adults, there are a few non-basket relatively unbranched endings (blue arrows and box; inset shows magnified view of the box) (C) Graph showing a decrease in non-basket endings (green) and increase in basket terminals (red) as a function of age. Note the number of non-basket terminals at P1 was greater than the total number of terminals at P21. (D) Histogram showing the greater complexity (higher branch order) of terminal arbors at P7 compared to P1 (n = 3 for each). Representative arbors from P1 and P7 are also shown in a schematized way to see branch order in the vertical axis.