The Localization of Acetylcholinesterase in the Cochlea

Introduction Recently we reported the results of experiments³,¹⁷demonstrating that acetylcholinesterase (AChE) was present in the nerve fibers within the cochlea. Koelle's method for the histochemical detection of AChE was employed. The technique was applied to the isolated cochleas of cats after removal of the outer bony wall. Portions of the osseous spiral lamina and organ of Corti were then teased onto glass slides for study. In brief, the histochemical method, described fully elsewhere,⁸⁻¹⁰consisted of incubating tissues in a solution of acetylthiocholine in the presence of cupric ion. The thiocholine liberated by enzymatic hydrolysis immediately formed a precipitate with cupric ions. The product, copper thiocholine, was converted later to copper sulfide when the specimen was treated with ammonium sulfide. Thus, copper sulfide, a stable and visible precipitate, was seen where AChE had been located. We satisfied ourselves that AChE was the material present in the cochlea by