Influence of malnutrition on developing rat peripheral nerves

Animals with experimentally induced neuropathies frequently fail to gain weight normally and appear poorly nourished. To determine whether or not malnutrition alone contributes to peripheral nerve dysfunction in these disorders, we subjected healthy 40-day-old rats to three grades of food restriction. After 4 weeks, food-restricted rats weighed 203 ± 5 (mean ± SE), 152 ± 12, and 97 ± 5 g, respectively, whereas control rats having free access to food weighed 379 ± 22 g. Posterior tibial nerves of food-deprived rats had smaller endoneurial areas, fewer large-diameter fibers, and shorter internodes than did the nerves of control animals. However, the number of fibers was similar to controls, and there was no evidence of active degeneration or demyelination. Motor and mixed nerve conduction velocities along the same nerves increased with age and did not differ among control and malnourished groups. In growing rats, food deprivation sufficient to impair somatic growth interferes with the maturation of large-caliber myelinated fibers, but does not effect standard electrophysiologic measurements of nerve function.