Expression of COX‐2 and NMDA receptor genes at the cochlea and midbrain in salicylate‐induced tinnitus

Abstract

The expression of the genes for cyclooxygenase (COX) and NMDA receptor (NR) has seldom been reported in tinnitus. We hypothesized that expression of COX-2 and NR was altered in the cochlea and midbrain in salicylate-induced tinnitus. Experimental study on mice. We evaluated the tinnitus score and mRNA expression levels of COX-2 and NR subtype 2B (NR2B) in the cochlea and midbrain in response to intraperitoneal injections of salicylate for 4 days. At day 4 of tinnitus induction, the mean weights of the whole body and midbrain did not change greatly in both control and salicylate groups. The tinnitus score was not elevated from day 1 to day 4 in the control group, but increased day by day in the salicylate group. The mRNA expression level of COX-2 decreased slightly in the salicylate group in the cochlea (1.1 ± 0.33 vs. 1.3 ± 0.49, P = .0752) and in the midbrain (0.9 ± 0.10 versus 1.0 ± 0.35, P = .0489). Inversely, the expression levels of the NR2B gene increased moderately in the salicylate group in the cochlea (3.7 ± 0.47 versus 2.3 ± 1.13, P < 0.0001) and in the midbrain (1.6 ± 0.64 versus 1.0 ± 0.44, P = .0007). Salicylate induced tinnitus and altered the expression of the COX-2 and NR2B genes in the cochlea and midbrain of mice. These findings might contribute to further understanding of pathophysiology and therapy of tinnitus.