Numerical patterns of axon regeneration that follow sciatic nerve crush in the neonatal rat.

Different proportions of axons regenerate in cutaneous nerves compared with muscle nerves after sciatic nerve crush in the rat. The questions here are whether or not these differences reflect the proportions of axons that regenerate in the different nerves from which these nerves arise and do the differences persist. The findings indicate that the numbers of axons that regenerate in the muscle nerves do not reflect the numbers in the nerve from which the muscle nerves originate and that these differences persist. This leads to the conclusion that some factors determining numbers of axons in the muscle nerves must operate distal to the lesion. Thus when one is considering mechanisms that control regenerated axon numbers after neonatal nerve crush, one must consider not only the lesion site but also branching and axon diversion far distally, presumably at the origin of the muscle nerves.