Noise exposure alters the response of outer hair cells to ATP.
The outer hair cells (OHCs) are one target of noise-induced effects. To date there are few studies which examine changes in the function of OHCs induced by noise exposure. There is increasing evidence that ATP may be a neuromodulator acting on OHCs. Therefore, we examined the possibility that the response to ATP may be altered by low-level noise exposure. ATP was tested on cation currents recorded from outer hair cells (OHCs) isolated from chronic noise-exposed guinea pigs and compared to currents recorded from normal control animals. The whole-cell variant of the patch-clamp technique was used. The incidence of response to 100 microM ATP was decreased in OHCs from noise-exposed animals as compared to controls when normal internal and external solutions were employed. When K+ was substituted by N-methyl-glucamine (NMG+) in the pipette solution, there were significant differences in the magnitudes of ATP-evoked currents between cells from noise-exposed and control animals. This was observed in both normal and 20 mM Ba2+ external solutions. In addition, the response to ATP exhibited a dependency on OHC length. In short OHCs (< 65 microns) from noise-exposed animals the magnitude of the response to ATP was significantly reduced. By contrast, the response in long OHCs (> 65 microns) from noise-exposed animals was increased. Results suggest that low-level noise exposure induces changes in OHCs which affect the response of the cell to ATP.
Chen
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Kresge Hearing Research Laboratory of the South, Department of Otorhinolaryngology and Biocommunication, Louisiana State University Medical Center, New Orleans 70112, USA.
Nenov
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Bobbin
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D000161:Acoustic Stimulation; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D003051:Cochlea / Q000166:cytology / Q000187:drug effects*; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000502:physiology*; D006317:Hearing Loss, Noise-Induced / Q000503:physiopathology; D017136:Ion Transport / Q000187:drug effects; D018408:Patch-Clamp Techniques
D000255:Adenosine Triphosphate