Cholinesterase and its Relation to the Nerve Endings in the Inner Ear

Abstract

The inner ear sensory epithelia in the guinea pig were stained with Holmstedt's modification of Koelle's thiocholine method for localization of cholinesterase activity and the staining reaction was studied with light and electron microscopy. Acetylcholinesterase activity was found as follows in specimens treated with the butyrylcholinesterase inhibitor Mipafox:

A. In the internal spiral bundle of all turns in the cochlea.

B. In nerve endings belonging to all rows of external hair cells in the basal coil.

C. In the nerve ending region of the two innermost rows of the external hair cells in the second and third turns, and only in the inner row of outer hair cells in the apical turn.

There was a close relation between the staining reaction and the localization of large granulated nerve endings in the cochlea.

In the vestibular sensory epithelia the precipitate caused by staining reation was found in the granulated nerve endings on the outside of the nerve chalices and at the bottom of the hair cells type II.

When acetylcholinesterase was inhibited, staining occurred with the solutions for demonstration of butyrylcholinesterase in the stria vascularis and diffusely in the cristae with most intense staining in the planum semilunatum.

The significance of the result is discussed.