Changes of myosin and its ATPase in "neuronally" and "mechanically" contralateral muscles after cross-reinnervation in normal and capsaicin-treated rats.
The extensor digitorum longus (EDL) muscle was cross-reinnervated by the soleus (SOL) nerve in normal and neonatally capsaicin-treated rats. After 5 months the muscles were investigated for their myofibrillar ATPase reaction and their myosin light and heavy chain composition. Besides the well known transformation of the cross-reinnervated EDL toward a slow muscle, muscular changes were also found in the contralateral leg. Although these changes were hardly detectable in the EDL muscle, a remarkable (70 to 100%) reduction of the fast type IIA fiber population was found in the SOL. The decrease of the number of IIA fibers (compared with time-matched controls) was paralleled by corresponding changes in the myosin light and heavy chain patterns. After the cross-reinnervation of a muscle, two kinds of contralaterality must be distinguished. In the experiments reported the cross-reinnervated EDL muscle remains "mechanically" contralateral to the EDL muscle of the other leg, while it becomes "neuronally" contralateral to the SOL muscle. Our results are interpreted as a symmetric "slowing down" of these "neuronally" contralateral muscles. Neonatal capsaicin treatment that decreased considerably the number of unmyelinated group IV afferent fibers did not influence the outcome of these experiments.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D008297:Male; D009132:Muscles / Q000201:enzymology / Q000294:innervation* / Q000378:metabolism; D009210:Myofibrils / Q000201:enzymology; D009218:Myosins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000251:Adenosine Triphosphatases; D009218:Myosins; D002211:Capsaicin