Direct evidence of nitric oxide production in the guinea pig organ of Corti

Production of nitric oxide (NO) in the organ of Corti of the guinea pig was investigated using the new fluorescence indicator 4,5-diaminofluorescein d iacetate for direct detection of NO. The organ of Corti, lateral wall of th e cochlea and isolated outer and inner hair cells were examined to locate N O production sites. The fluorescence intensities were augmented by stimulat ion with L-arginine or glutamate, and significantly increased after inocula tion with lipopolysaccharide. This is the First direct evidence of NO produ ction in the cochlea. NO may play an important role in the physiology of th e organ of Corti and may also be involved in hearing disorders.