Nitric oxide uncouples gap junctions of supporting Deiters cells from Corti's organ

Supporting cells of Corti's organ are electrically coupled via gap junction s. They probably serve to maintain the unique cochlear environment that is required for normal sensory function. In this study we used input capacitan ce measurements under whole-cell voltage-clamp conditions to evaluate the e ffects of nitric oxide on gap junctional communication between pairs of iso lated supporting Deiters cells. We show that the nitric oxide (NO) donor so dium nitroprusside causes the uncoupling of Deiters cells, and that an NO s ynthase inhibitor blocks the effect. The cGMP analogue 8-bromo-cGMP also un couples Deiters cells. With either treatment, the input capacitance of pair s of Deiters cells drops to single-cell levels within minutes of applicatio n, indicative of electrical uncoupling. We surmise that the NO/cGMP pathway may serve to modulate normal cochlear homeostasis and possibly plays a rol e in ototoxic mechanisms.