Ultrastructural study of effect of ACTH4-10 on nerve regeneration; axons become larger in number and smaller in diameter.

Electron-microscopic analysis of the regenerating sciatic nerve in the rat showed that ACTH4-10 treatment stimulated the number of regenerating myelinated and unmyelinated fibers to a similar degree. Fourteen days following a crush lesion of the sciatic nerve, 23% more regenerating fibers were present in the ACTH4-10-treated group of animals. The increase in number of regenerating fibers was accompanied by a comparable decrease in axon diameter. The ACTH4-10 treatment did not change the number of lamellae in the myelin sheath.