コルチ器の外毛神経終末に関する研究 ＳＥＭによる観察

Abstract

With the use of double sided adhesive tape in the microdissection, the space of Nuel in all turns of the cochlea can be exposed and observed by scanning electron microscope. The nerve endings in the basal turn were exposed entirely in the endolymphatic space, whereas in the upper turns almost all nerve endings were covered by the Deiters cell bulge. A gradual decrease in the number and size of nerve endings from the lower basal turn toward the apical turn was observed. In the basal turn, there were about 6-12 nerve endings on the surface of the lower pole of the outer hair cell. The size of the majority of these nerve endings was between 1 and 3.5 micrometers. In the apical turn, about 4-6 nerve endings with diameters of 0.5 to 2 micrometers were seen around the tip of the lower pole of the outer hair cell. The shape of the nerve endings also changed from spindle shaped in the basal turn to gradually rounded in the upper turns. In addition to the well known nerve endings on the lower pole of the outer hair cells, nerve endings located high on the outer hair cells were also observed. These high nerve endings varied in size and were located at various distances from the lower pole of the outer hair cell.In guinea pigs treated with high doses of streptornycin or kanamycin, there was no pathological change of the nerve endings 24 hours after ten consecutive days of treatment or after the completion of injections given every other day. Although the nerve endings seemed to be more resistant to these ototoxic drugs, the outer hair cells consistently showed shrinkage, especially at the basal location where an ototoxic effect on the hair cell cilia was also observed. It appears that shrinkage of the outer hair cells may be an early sign of an ototoxic effect on the organ of corti.