Cross‐innervated mammalian skeletal muscle: histochemical, physiological and biochemical observations

Abstract

Cross-innervation of the slow soleus and fast flexor hallucis longus or flexor digitorum longus muscles was performed in new-born kittens and rabbits and in adult cats. The effects on the histochemical and structural properties of the muscle were studied and compared with the changes in the contractile properties. Cross-innervation produced a dramatic change in histochemical pattern in the fast muscles, with the development of areas of muscle fibers indistinguishable from normal soleus muscle. The converse change from the histochemical pattern of slow soleus to that of fat muscle also occurred but has been less consistent. The neural influence determining the contractile properties of fast and slow muscle also has a profound controlling influence on the structure and metabolic activity of the muscle fibers. No significant changes could be demonstrated biochemically in the ATPase activities of the fast and slow muscles following cross-innervation.