Expression changes in IC GABA receptors in the auditory midbrain of young adult and aging presbycusis mice.

We performed a microarray analysis of auditory midbrain (inferior colliculus, IC) mRNA from young adult CBA mice (controls) with good hearing, middle aged (MA) with good hearing, and old mild (MP) and severe (SP) presbycusic CBA mice. Fold Change data derived from RMA normalization revealed that the overall GABA receptor alpha 6 expression profiles for MA, MP and SP were down-regulated relative to young adult controls with good hearing. Relative real-time PCR for five GABA receptors confirmed this age-related down regulation quantitatively. Functional hearing data: Auditory Brainstem Responses (ABR) enriched the analysis to select the probe-sets that changed with age and hearing loss by the linear regression best-fit line model technique. GABA receptor genotype-phenotype correlations with auditory functional data indicated that GABA-receptor subtypes are under expressed in SP mice. Hierarchical clustering (HC) analyses yielded statistical significance of normalized GeneChip data Real-time PCR showed that Gabra6, GABA B receptor 1 (Gabbr1), and Gaba transporter protein Slc32a1 may be involved in physiological changes that occur in age-related hearing loss.

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