[Changes in the number and distribution of intramembranous particles of electric organ synaptosomes of Torpedo during synaptic activity].

Cholinergic synaptosomes were depolarized with KCl or treated with a venom extracted from the annelid Glycera convoluta. This venom was shown to increase considerably the frequency of the miniature endplate potentials at neuromuscular junctions. The synaptosomes were frozen and fractured in the absence of any fixative or cryoprotectant. Synaptic activity decreased the number of small (6 to 8 nm) particles in the P faces of the presynatic membrane, while the large particles (above 8 nm) increased on both P and E faces. It is suggested that these modifications are related to ionic flux or more directly to the release of transmitter.