Loss of glycine receptors containing the α3 subunit compromises auditory nerve activity, but not outer hair cell function

Publication date: Available online 18 May 2016
Source:Hearing Research
Author(s): Julia Dlugaiczyk, Dietmar Hecker, Christian Neubert, Stefanie Buerbank, Dario Campanelli, Cord-Michael Becker, Heinrich Betz, Marlies Knipper, Lukas Rüttiger, Bernhard Schick
Inhibitory glycine receptors containing the α3 subunit (GlyRα3) regulate sensory information processing in the CNS and retina. In previous work, we demonstrated the presence of postsynaptic GlyR alpha3 immunoreactivity at efferent synapses of the medial and lateral olivocochlear bundle in the organ of Corti; however, the role of these alpha3-GlyRs in auditory signalling has remained elusive. The present study analyzes distortion-product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs) of knockout mice with a targeted inactivation of the Glra3 gene (Glra3^-/-) and their wildtype littermates (Glra3^+/+) before and seven days after acoustic trauma (AT; 4 to 16 kHz, 120 dB SPL, 1 h).Before AT, DPOAE thresholds were slightly, but significantly lower, and DPOAE amplitudes were slightly larger in Glra3^-/- as compared to Glra3^+/+ mice. While click- and f-ABR thresholds were similar in both genotypes before AT, threshold-normalized click-ABR wave I amplitudes were smaller in Glra3^-/- mice as compared to their wildtype littermates. Following AT, both the decrement of ABR wave I amplitudes and the delay of wave I latencies were more pronounced in Glra3^-/- than Glra3^+/+ mice. Accordingly, correlation between early click-evoked ABR signals (0 to 2.5 ms from stimulus onset) before and after AT was significantly reduced for Glra3^-/- as compared to Glra3^+/+ mice. In summary, these results show that loss of α3-GlyRs compromises suprathreshold auditory nerve activity, but not outer hair cell function.



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