The neuromuscular junction in response to endurance training

Abstract

Endplate and nonendplate cholinesterase and choline acetyltransferase activities were measured in muscles of untrained and endurance-trained rats to determine the relationship of these enzymes to known physiologic and morphologic properties of specific types of muscle fibers, and to determine the responsiveness of these presynaptic and postsynaptic enzymes to chronic muscular activity. In the trained soleus and red and white vastus lateralis, endplate cholinesterase activity was significantly ( P < 0.05) higher in the trained than in the nontrained endplate region of the white vastus lateralis muscle only. Endplate cholinesterase activities were greater than nonendplate values in both trained and untrained muscles. Choline acetyltransferase activity in soleus and red and white vastus lateralis was not affected significantly by endurance training. The selective training effect on the cholinesterase activity of the fast-twitch glycolytic fibers contrasts with the small change in oxidative metabolism in fast-twitch glycolytic fibers previously reported in endurance-trained rats.