title: ATP-gated ion channels mediate adaptation to elevated sound levels.
abstract: The sense of hearing is remarkable for its auditory dynamic range, which spans more than 10(12) in acoustic intensity. The mechanisms that enable the cochlea to transduce high sound levels without damage are of key interest, particularly with regard to the broad impact of industrial, military, and recreational auditory overstimulation on hearing disability. We show that ATP-gated ion channels assembled from P2X2 receptor subunits in the cochlea are necessary for the development of temporary threshold shift (TTS), evident in auditory brainstem response recordings as sound levels rise. In mice null for the P2RX2 gene (encoding the P2X2 receptor subunit), sustained 85-dB noise failed to elicit the TTS that wild-type (WT) mice developed. ATP released from the tissues of the cochlear partition with elevation of sound levels likely activates the broadly distributed P2X2 receptors on epithelial cells lining the endolymphatic compartment. This purinergic signaling is supported by significantly greater noise-induced suppression of distortion product otoacoustic emissions derived from outer hair cell transduction and decreased suprathreshold auditory brainstem response input/output gain in WT mice compared with P2RX2-null mice. At higher sound levels (≥95 dB), additional processes dominated TTS, and P2RX2-null mice were more vulnerable than WT mice to permanent hearing loss due to hair cell synapse disruption. P2RX2-null mice lacked ATP-gated conductance across the cochlear partition, including loss of ATP-gated inward current in hair cells. These data indicate that a significant component of TTS represents P2X2 receptor-dependent purinergic hearing adaptation that underpins the upper physiological range of hearing.
authors.affiliation: Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia. g.housley@unsw.edu.au
authors.forename: Gary D
authors.initials: GD
authors.lastname: Housley
authors.forename: Rachel
authors.initials: R
authors.lastname: Morton-Jones
authors.forename: Srdjan M
authors.initials: SM
authors.lastname: Vlajkovic
authors.forename: Ravindra S
authors.initials: RS
authors.lastname: Telang
authors.forename: Vinthiya
authors.initials: V
authors.lastname: Paramananthasivam
authors.forename: Sherif F
authors.initials: SF
authors.lastname: Tadros
authors.forename: Ann Chi Yan
authors.initials: AC
authors.lastname: Wong
authors.forename: Kristina E
authors.initials: KE
authors.lastname: Froud
authors.forename: Jennie M E
authors.initials: JM
authors.lastname: Cederholm
authors.forename: Yogeesan
authors.initials: Y
authors.lastname: Sivakumaran
authors.forename: Peerawuth
authors.initials: P
authors.lastname: Snguanwongchai
authors.forename: Baljit S
authors.initials: BS
authors.lastname: Khakh
authors.forename: Debra A
authors.initials: DA
authors.lastname: Cockayne
authors.forename: Peter R
authors.initials: PR
authors.lastname: Thorne
authors.forename: Allen F
authors.initials: AF
authors.lastname: Ryan
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects; D003051:Cochlea / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism / Q000503:physiopathology; D015640:Ion Channel Gating / Q000187:drug effects*; D007473:Ion Channels / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009622:Noise; D058476:Receptors, Purinergic P2X2 / Q000172:deficiency; D013016:Sound
chemical_list: D007473:Ion Channels; D058476:Receptors, Purinergic P2X2; D000255:Adenosine Triphosphate