The mean number of puncta immunoreactive for PV, vGAT, or γ2 overlapping AIS is decreased in adult compared with 3-month-old monkeys. A, Single channel images of a deconvolved image stack (five z-planes) from an adult monkey section multilabeled for NeuN/AnkG, PV, vGAT, and γ2. Solid arrowhead, PVChC bouton; open arrowhead, ChC bouton with no visually detectable PV. A 3× zoom of the boxed region is shown below each channel. Scale bar, 10 μm. B, Table showing the mean number of ChC boutons per AIS (all ChC), ChC boutons classified as containing PV (PVChC), and ChC boutons classified as being PV-immunonegative (ChC_PVneg). C, Single channel images of a deconvolved image stack (five z-planes) of an adult monkey section multilabeled for NeuN/AnkG, PV, vGAT, and γ2. Arrows, solid arrowheads, and the open arrowhead point to AIS differentially innervated by PVChCs. Scale bar, 10 μm. D, Histograms of PV (mean 3-month-old = 19.2, adult = 11.8), vGAT (mean 3-month-old = 21.8, adult = 14.2), and γ2 (mean 3-month-old = 26.7, adult = 15.3) -IR puncta per AIS in 3-month-old (black) and adult monkeys (gray). Arrowheads point to respective means. A randomly selected 500 AIS from each age group is displayed.