Influence of an experimental hindlimb maldevelopment on axon number and nodal spacing in the rat sciatic nerve

In neonatal rat pups the femoral and tibial epiphyseal cartilages on the left side were coagulated with a microcautery device. The subsequent femoral and tibial growth in length was markedly restricted on the left side, but the foot and the pelvic region exhibited normal longitudinal growth. After 6 months the sciatic nerves were removed from both sides. Electron microscopic analysis of nerve specimens from the stunted side revealed that the number of axons was 20% less compared to control specimens. Light microscopic examination of teased preparations showed a normal nodal spacing in the pelvic segment but abnormally short internodes in the femoral segment of the left sciatic nerve. These results suggest that the number of axons in the rat sciatic nerve adapts to a target maldevelopment that sets in neonatally, and that internodal elongation during development proceeds according to the local growth in length of the nerve rather than to the length growth of the whole nerve.