Ipsi-and contralateral changes in rabbit soleus myosins by cross-reinnervation.

Cross reinnervation of soleus muscle in the adult rabbit induces changes in myosin light chain and isomyosin patterns. The transformation of the light chain pattern consists of a decrease in LC1's and LC2, and an induction of the three fast type myosin light chains. The transition in the isomyosin pattern consists of a decrease of the slow type isomyosin SM and an induction of fast type isomyosins FM1, FM2, and FM3 normally seen in fast-twitch rabbit muscle. An additional isomyosin of intermediate electrophoretic mobility, which resembles isomyosin 4 of rat muscle, is induced. These changes are not restricted to the cross-reinnervated soleus muscle but are also seen, although to a lesser extent, in the contralateral soleus muscle. It is suggested that the altered afferent activity brought about by cross-reinnervation, is neurally transmitted to the opposite side and leads to a change in efferent activity to the contralateral muscle.