XXXI Adrenergic Control of Cochlear Blood Flow

Nerve fibers which mediate constriction of blood vessels were first discovered in 1851 by Bernard! when he noted vasodilation in "the ear" of a rabbit following transection of the ipsilateral sympathetic nerve supply in the neck.Although adrenergic innervation of blood vessels of the inner ear has been recently confirmed, the control mechanism of this circulation has not been explained.The first anatomical observations of the innervation of blood vessels in the inner ear was reported in 1937 by Lorente de No,2 who demonstrated nerve fibers passing from the cochlear nerve to the blood vessels in the modiolus of the rat.Smith" reported more detailed observations of the innervation of the cochlear vessels of the guinea pig.She found numerous unmyelinated nerve fibers accompanying the labyrinthine artery and its coiled secondary branches without connection to the cochlear nerve.Smith did not find any nerve fibers accompanying the radiating arterioles and capillaries.Histochemical preparations for catechol amines in the cochlea have demonstrated adrenergic nerve fibers along the cochlear vessels.In 1964, Nagakura" reported that fluorescence of catechol amine oxydase was found in the muscle layer of the cochlear artery and its secondary branches in the stria vascularis and in the spiral