S228 – Direct Round Window Drug Application and Ototoxicity in Rats

Abstract

Objectives 1) Manage to introduce ototoxic drugs, such as kanamycin and furosemide, directly on the round window in rats. 2) Use a purified gelatine sponge as a proper delivery vehicle. The purpose of the study is to assess the validity of this method to provoke local ototoxicity. Methods We carried out an experimental design with 3 groups of 6 male Wistar rats. The bulla and round window membrane were exposed using a ventral approach. In the first control group we only made a hole in the tympanic bulla. Second control group was treated with saline solution. The problem group was treated with 20 mg/kg of kanamycin and 5 mg/Kg of furosemide-soaked gelatine sponge directly upon the round window membrane. Cochlear function was assessed through tone burst auditory brainstem response (ABR) threshold (dB) and peak latency (ms) measurements. Anova with bonferroni correction was used (p level=0.05). Results All animals treated with kanamycin and furosemide exhibited significant increase in ABR threshold (x = 51.25 dB; SD = 6.29; p = 0,001) in contrast to the other groups, whose ABR thresholds did not show significant differences before and after treatment(x=31,50 dB; SD=5.53); and not significant increase in peak latencies I (x = 0.22 ms; SD = 0.12), II (x = 0.22 ms; SD = 0.20) and IV (x = 0.21 ms; SD = 0.18). Conclusions The ventral approach and placement of kanamycin and furosemide-soaked gelatine sponge directly upon the round window membrane represents a reliable method for ototoxicity in rats.