Age differences in the morphology of posterior tibial nerves of mice

Abstract

Abstract Light microscopic examination of posterior tibial nerves of C57BL/10 female mice at 3, 8 and 26 months of age revealed an age‐related decrease in the total number of myelinated fibers per nerve with a fairly uniform loss across all caliber of fibers present. However, the size of the individual nerves increased with age as did also mean axon diameter of individual fibers and the proportion of connective tissue between fibers in the older nerves. Ultrastructural comparisons revealed an increase in mean axone circumference of myelinated fibers between 3 and 8 months and, of unmyelinated fibers between 8 and 26 months. Also, there was a significant decrease in mitochondrial concentration in myelinated fibers between 8 and 26 months of age. There was no change in blood vessels, myelin sheath thickness, concentration of unmyelinated fibers per nerve, and in the concentration of filaments and tubules in myelinated and unmyelinated axons in relation to increasing age.