Fig 1: GABA myelinated axons have more CNP in their myelin. A, Volume reconstruction of 21 serial sections from human cortical layer 5, immunostained with CNP (magenta) and MBP. B, Three consecutive sections through a GABA myelinated axon immunolabeled for CNP (magenta) and MBP (white). The first section is also shown immunolabeled for GABA. C, Thicker GABA axons (0.6–1.2 µm in diameter) have significantly more CNP in their myelin sheath compared to nonGABA axons of similar thickness. Center lines in boxplots show the medians, box limits indicate the 25th and 75th percentiles as determined by R software; whiskers extend 1.5 times the interquartile range from the 25th to the 75th percentiles, outliers are represented by dots. For the boxplot on the left (axon diameter 0.1–0.6 µm), n = 341 nonGABA and n = 98 GABA myelinated axons from two samples), and for the boxplot on the right (axon diameter 0.6–1.2 µm), n = 142 nonGABA and n = 34 GABA axons from two samples).