[The ultrastructure of the neuromuscular synaptic terminal in the frog after denervation]

Ultrastructure of certain myoneural terminals were studied on serial sections on day 3, 5 and 8 after denervation. Ultrastructure of the terminal proximal and distal regions and Schwann cell were studied by means of morphometry and reconstruction of single terminals. On day 3 after denervation Schwann cell is activated in terminal proximal regions more rapidly than in distal ones with contractility in the terminal proximal region being more significant than in distal. On day 5 after denervation changes cover both initial and terminal regions and on day 8 almost all the regions where terminal were placed earlier were occupied with Schwann cell. A suggestion is made that structural changes in the Schwann cell-terminal system are the major contributors to decrease of synaptic discharge in early stages of denervation and appearance of Schwann cell potentials in more late ones.