Selective reinnervation of the rat serratus anterior muscle following denervation and partial target removal.

The rat serratus anterior (SA) muscle is reinnervated by cervical roots C6 and C7 with a topographic bias following transection or freezing of the long thoracic nerve. The study reported here was undertaken to determine the specificity of regenerating motoneurons when the size of the target SA muscle was reduced. After crush and removal of the caudal half of the muscle, a rostrocaudal map was reestablished that was no different from control or crush alone. Rostral (C6) axons dominated the innervation of muscles deprived of their caudal sectors. Input from caudal (C7) axons was significantly reduced. These results may be explained by preferential pathways or a competitive advantage held by rostral axons reinnervating rostral sectors to the detriment of caudal axons.