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KMID : 0361020130560020061
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Korean Journal of Otolaryngology - Head and Neck Surgery
2013 Volume.56 No. 2 p.61 ~ p.67
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Mechanism of Efferent Inhibition in Cochlear Hair Cell
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Im Gi-Jung
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Abstract
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Efferent neurons release acetylcholine to inhibit sensory hair cells of the inner ear. The α9α10 nicotinic acetylcholine receptor (nAChR) mediates efferent inhibition of hair cell function within the auditory sensory organ. Gating of the nAChR triggers inward calcium current, and leads to activation of calcium dependent, small-conductance potassium (SK) potassium channels to hyperpolarize the hair cell. Through SK channels, large potassium outflow occurred, and outer hair cell was hyperpolarized. Thus, amplification of sound and sensitivity of hearing was reduced or modulated by efferent inhibition. In efferent system, main calcium providers to SK channel are nAChR and synaptic cistern, which contribution to efferent inhibition is different between avian and mammalian species. Calcium permeation is more effective in nAChRs of mammalian cochlea than avian cochlea, and mammalian calcium permeability of nAChRs is about 3 times more than avian hair cell. Thus, nAChRs is a main component of efferent inhibition in mammalian cochlear hair cell system.
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KEYWORD
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Acetylcholine, Calcium, Cochlea, Hair cell, Nicotinic receptor
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