The inward-rectifier K(+) channel Kir4.1 is responsible for maintaining cochlear homeostasis and restoring neural excitability. The large-conductance calcium-activated K(+) channel (BK(Ca)) plays a key role in phase locking signals in the mammalian inner ear. To evaluate the influence of mitochondrial dysfunction on the expression and subcellular localization of these channels, 3-nitropropionic acid (3-NP) was administered to rat round window membranes for 30 min. Auditory brainstem response was measured both before and 2 hr after 3-NP administration. Immunofluorescent confocal microscopy was used to measure the expression and subcellular localization of Kir4.1 and BK(Ca). Alexa Fluor 568-labeled bovine serum albumin (BSA) was applied to round window membranes as a tracer to explore the cochlear distribution of drug delivery and was detected in the lateral wall, spiral ganglion, cochlear nerve, and organ of Corti. Hearing loss of 23 (+/-4.4 SE) and 58 (+/-6.7 SE) dB developed in rats treated with 0.3 and 0.5 mol/liter of 3-NP, respectively. BK(Ca) was visualized in the cellular membrane and cytoplasm in the upper and middle region of inner hair cells, and it was not affected by 3-NP. Kir4.1 was detected in intermediate cells of the stria, Deiter's cells, and spiral ganglion satellite cells. Kir4.1 failed to reach the perineural cytoplasm of the satellite cells after 3-NP treatment. The results of this study suggest that mitochondrial dysfunction disrupts trafficking of Kir4.1 in spiral ganglion satellite cells.
2008 Wiley-Liss, Inc.