Effect of transposition on contractile and histochemical properties of muscle.

In 16 rats, the extensor digitorum longus (EDL) - a fast muscle - was grafted, complete with its innervation, into the bed of the (removed) soleus - a slow muscle. Following the transposition, performed on one side only, EDL recovered and showed the contraction time of the contralateral EDL that served as control. However, as demonstrated histochemically, the transposed EDL exhibited a different succinic dehydrogenase activity: it acquired the muscle fiber pattern of the slow red soleus muscle. This method of transposition of muscle plus nerve allows the study of nerve-muscle relationships with respect to a multiple regulation of muscle properties, including the decisive role of neuronal specificity and other mechanisms such as substrate (oxygen) supply.