Correlation between the acetylcholinesterase content in motor nerves and their muscles

A comparative study of the activity and distribution of the molecular forms of acetylcholinesterase (AChE) in slow and fast-twitch systems was performed in normal and dystrophic 129/ReJ mice and in rats. As compared to its fast-twitch counterparts, the soleus muscle of the normal mouse as well as of the rat showed a distinct content in AChE characterized by a slow activity, a low proportion in G4 and a relative increase in the A8 form. In the dystrophic condition, the fast muscles exhibited an AChE content typical of the soleus muscle, in particular low G4 and a relative increase in A8. In contrast, the soleus muscle was only slightly affected by the disease. The soleus nerve in the normal mouse and rat showed a significant reduction in both total AChE activity and G4 content as compared to nerves of fast-twitch muscles. In the dystrophic mouse, the AChE content of the nerves to fast muscles was similar to that of the soleus nerve in the normal condition. These results reveal a strict correlation between the AChE content in both nerve and muscle, and the twitch properties. The results obtained in dystrophic mice suggest that neural AChE is the determinant factor in this relationship. A mechanism by which neural AChE may regulate muscle AChE is proposed and discussed in the light of recent advances on the neuromuscular junction.