The Significance Of (CA)n Tandem Repeat in GABA(A) Beta-3 Subunit Gene in Tinnitus Manifestation



Year of publication 2014
Type Article in Periodical
Magazine / Source Česká a Slovenská neurologie a neurochirurgie
MU Faculty or unit

Faculty of Medicine

Field ORL, ophthalmology, stomatology
Keywords tinnitus; GABA-A receptor; auditory evoked potentials
Attached files
Description Study aim: Study objective was to explore associations between manifestation of tinnitus, auditory evoked potentials and genetic background of gamma-aminobutyric acid type A (GABA(A) receptors) to support the disinhibited feedback hypothesis of tinnitus generation. Materials and methods: A population of 131 patients was assessed for severity of hearing loss, quantification of tinnitus, mid-latency responses (MLR) and brainstem auditory evoked potentials (BAEP), and (CA)n tandem repeat polymorphism in GABA(A) Beta-3 subunit gene to establish any correlation with manifestation of tinnitus. Results: It was observed that tinnitus score correlates with V/III amplitude ratio in BAEP (R = 0.22, p < 0.001) and with mean pure tone audiometry (PTA) threshold (R = 0.22, p = 0.017). Analysis of the MLR results showed a significant correlation between the PA wave amplitude and the tinnitus score (R = 0.31–0.37; p < 0.001). MLR result analysis showed no statistically significant correlation between the wave amplitudes and the mean auditory threshold. An analysis of a subgroup with shorter clinical history (less than nine months) revealed a statistically significant difference in the tinnitus score in relation to the genotype of (CA)n tandem repeat of the GABRß3 receptor subunit gene (p = 0.002). This result was also consistent with the distribution of the PA wave amplitude in the given subpopulation. Conclusion: Our findings indicate existence of two main regulatory mechanisms of tinnitus generation: first, the brainstem mechanism is dependent on the severity of the hearing loss; second, the cortical mechanism is likely to be dependent on the genotype of (CA)n tandem repeat in GABA(A) beta-3 subunit gene.
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