REGENERATION OF AFFERENT AND EFFERENT FIBERS TO MUSCLE-SPINDLES AFTER NERVE INJURY IN ADULT CATS

The nerves to cat peroneus longus and tenuissimus muscles were either cut or crushed close to the muscle and the afferent and efferent nerve supply to the muscle spindles was studied electrophysiologically between 2-32 wk later. Recovery was more rapid and complete after crush than section for both afferent and efferent fibers. After recovery from either procedure normal primary and secondary afferents and static and dynamic .gamma. efferent fibers were found. Some abnormally occurring neurons were found. One group consisted of .beta. fibers which had a static action on muscle spindles. Static .beta. fibers are very rarely found in normal muscles. Apparently some guidance mechanism exists which after crush injuries of nerves may restore muscle receptor function almost to normal. Even after nerve section some muscle spindles may become correctly reinnervated.