Glyoxylic acid in the study of autonomic innervation in the gerbil cochlea.

The autonomic innervation of the inner ear has been investigated earlier, yet questions concerning the origin, function, extent, and distribution of sympathetic nerves in the cochlea still remain unanswered. This study investigates the extent and distribution of adrenergic nerves in the cochlea. Our procedure combines the glyoxylic acid method of catecholamine fluorophore identification with rapid dissection, decalcification, and whole-mount slide preparation techniques to topographically trace the adrenergic innervation of the cochlear infrastructure. We have demonstrated that perivascular adrenergic innervation extends beyond the immediate branches of the modiolar artery and reaches into radiating arterioles. These findings also suggest the possibility of segmental regulation of cochlear blood flow.