Histochemical Study of the Acetylcholinesterase Activity in the Inner Ear of the Squirrel Monkey

Abstract

Perfusion-fixation was performed on the squirrel monkey, whose temporal bones were then decalcified in cold EDTA (ethylenediamine tetracetate) solution. Gholinesterase (ChE) activity was demonstrated on frozen sections of these bones. ChE in the efferent fibers of the inner ear was identified as acetylcholinesterase (AChE) by using specific inhibitors. Fine, scattered AChE containing fibers in the cochlear nerve were observed crossing the glial-Schwann sheath junction which were not a part of Rasmussen's bundle. After transection of the cochlear nerve, these fine fibers lost AChE activity, suggesting they were of efferent nature. In the organ of Corti, both the upper tunnel radial and basilar bundles were found to show AChE activity. These two bundles apparently contained efferent fibers.