Catecholaminergic innervation of the inner ear

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Abstract
Cochlear blood flow has been shown to be controlled, in part, by the sympathetic nervous system. We have used immunocytochemical staining for tyrosine hydroxylase (TH) to further demonstrate the extent of catecholaminergic innervation of the cochlea. Deeply anesthetized Mongolian gerbils were systemically perfused with phosphate-buffered saline, followed by 4% paraformaldehyde. The cochleae were dissected out and post-fixed for 3 hours in 4% paraformaldehyde. They were then incubated in anti-TH antibody and subsequently processed using the avidin-biotin immunoperoxidase method. Microscopic examination of whole-mounted tissue revealed many immunoreactive fibers on the spiral modiolar artery. TH-positive fibers have also been found on both radiating arterioles and radial collecting venules, which has not been previously reported. With innervation of these small vessels, blood flow in the cochlea may be segmentally controlled. We also further describe the organization of TH-positive fibers in the osseous spiral lamina.