The Response of Mammalian Cochlear Hair Cells to Acoustic Overstimulation
The distinct morphological division of the inner and outer hair cells (IHC, OHC) within the organ of Corti, and their respective innervation, suggest two separate roles for these receptors in normal auditory function. The IHCs receive a massive afferent innervation while the afferent innervation of the OHCs is comparatively sparse with a large number of efferent synapses on their basolateral surfaces [1,2]. This has contributed to speculation that there is a division of labour in the cochlea, with the IHCs playing a sensory role and the OHCs fulfilling a motor role, controlling the mechanical stimulus delivered to the IHCs. As primary receptors, the IHC and the OHC appear to be vulnerable links in the auditory pathway during acoustic overstimulation and therefore prime targets for the site and origin of noise-induced hearing losses (NIHL). We have attempted to substantiate this hypothesis in a series of experiments by recording directly from the IHCs and OHCs during conditions of acoustic overstimulation. The results suggest that functional differences in the behavior of these two cell groups to overstimulation may underlie the cellular basis for NIHL. These cellular changes probably account for the altered activity of the afferent fibers we have monitored in the spiral ganglion of the cochlea in previous studies, at least for temporary losses of auditory sensitivity and possibly, the more significant, permanent losses.
KeywordsHair Cell Receptor Potential Outer Hair Cell Basilar Membrane Spiral Ganglion
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