Use of muscle fibrillation for tracking nerve regeneration.

Individual muscle fibers in denervated muscle demonstrate repetitive, spontaneous contraction. Such fibrillation activity disappears in denervated muscle if reinnervation occurs, but this relationship has not been formally studied. To test whether the disappearance of fibrillation can be used to track nerve regeneration, we quantified the presence and subsequent disappearance of electromyographic (EMG) fibrillation potentials and fibrillation-related movement in the rat tongue after unilateral hypoglossal nerve crush at two locations. In mice, fibrillation movement of vibrissae were monitored after unilateral facial nerve crush and compared with the return of symmetrical vibrissae sweeping movements. In both of these rodent cranial motor systems, there was a conspicuous loss of fibrillation at a time when reinnervation is known to take place, suggesting that the visual appearance of fibrillation-related movement can be used as a simple, noninvasive means of tracking nerve regeneration in these popular experimental motor systems.