V Adrenergic Innervation of the Cochlea

Abstract

By means of a modified Falck''s fluorescence method, the adrenergic fibers presented by specific fluorescence of noradrenaline (norepinephrine) were found in the guinea pig''s cochlea. The adrenergic fibers in the cochlea appeared always to run with blood vessels. They are distributed most richly surrounding the arteries in the internal auditory meatus and modiolar canal. Along these arteries, one group of them reaches up to the coiled secondary branch of the cochlearis artery within the bony canal of the modiolar wall. Another group ramifies into many delicate fibers along small blood vessels entering within the cochlear nerve trunk. The fibers course with cochlear nerve fibers fromthe modiolar canal through the spiral ganglion and radially within the osseous spiral lamina, and reach to the small vessels below the inner pillar or to a part of the spiral vessels beneath the tunnel. The adrenergic fibers were not found at all in the vicinity of the veins and the radiating arterioles, in the spiral ligament and strial area, in the organ of Corti and in the spiral limbus. The specific fluorescence disappeared after administration of reserpine. The various sympathetic denervations made it evident that the adrenergic fibers arise from the homolateral cranial cervical ganglion as a sympathetic nerve and course through the internal carotid nerve along the internal auditory artery to the cochlea and vestibule. The extirpation of other cervical ganglions or other branches of the cranial cervical ganglion showed no influence on the specific fluorescence.