HISTOCHEMICAL LOCALIZATION OF CHOLINESTERASES IN COCHLEAR NUCLEI OF CAT, WITH NOTES ON ORIGIN OF ACETYLCHOLINESTERASE-POSITIVE AFFERENTS AND SUPERIOR OLIVE

This study was carried out in order to correlate the distribution of cholinesterases in the cat cochlear nuclei with the cytoarchitecture and terminal areas of afferent fiber tracts. Formaldehyde-fixed frozen sections were stained by the thiocholine method using acetylthiocholine and butyrylthiocholine iodides as substrates and Mipafox as a specific inhibitor of butyrylcholinesterase (BuChE). The acetylcholinesterase (AChE) activity appeared to be associated with neurons while the BuChE reaction probably was confined to glial elements. Short incubation revealed only a few AChE positive structures which appeared to form a continuous pathway leading from certain cells in the superior olivary complex via the olivocochlear bundle to the molecular and granular cell layers of the cochlear nuclei. The probable role of this AChE-positive pathway in the central control of the pyramidal cell activity in the cochlear nuclei is discussed. Prolonged incubation resulted in a more widespread AChE reaction, and in these sections most cell areas of the cochlear nuclei could be defined by their staining properties. The AChE-positive plexus of the large and small spherical cell areas may represent the terminal arborization of the facilitatory cholinergic pathway found physiologically by Whitfield and Comis50,51 to arise in the lateral superior olive on the same side. © 1969.