Localization of acetylcholinesterase in the rat myoneural junction

Summary The distribution of myoneural acetylcholinesterase (AChE; EC. 3.1.1.7) was studied electron microscopically with the copper ferricyanide method at pH 6.0, using acetylthiocholine iodide as substrate and iso-OMPA to exclude other cholinesterase activity.It was observed that the results obtained with this method are affected by changes in the reaction temperature, inhibitor concentration and fixation time. Changes which retard the rate of hydrolysis of AChE were observed to transfer the localization of the reaction endproduct in intact junctions from the extracellular side of the postsynaptic membrane to the intracellular side of the postsynaptic membrane. From the results it is concluded that the site of most intense AChE corresponds to the region of increased subsarcolemmal electron density of the postsynaptic membrane.