Fig 1: GABA myelinated axons have more mitochondria. A, A single 70-nm section from layer 4 of human cortex immunolabeled with GABA (red), PLP (white), MDH2 (magenta), TOMM20 (green), and VDAC1 (cyan). B, The boxed area in A is enlarged to show two immunolabeled mitochondria, with the MDH2 mitochondrial matrix protein surrounded by the outer mitochondrial membrane proteins TOMM20 and VDAC1. C, Five serial sections through axons 1 and 2, marked on A, top section. Axon 1 is nonGABA and axon 2 is GABA. Adjacent to axon 2, there is also a nonGABA axon. D, Boxplots of the immunofluorescence for MDH2, TOMM20, and VDAC1 within nonGABA and GABA myelinated axons. Center lines 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, n = 88 and n = 41 axons for MDH2, n = 95 and n = 43 axons for TOMM 20, and n = 97 and n = 47 axons for VDAC1, from layers 3a through 5 from three different samples.