Direct drug application to the round window: A comparative study of ototoxicity in rats

Abstract

Objective: To assess the validity of inducing ototoxicity in rats by applying a sponge soaked in kanamycin and furosemide on the round window. Study Design: Basic, randomized, nonblind experimental study. Setting: Animal models of cochlear damage and reliable methods of local drug delivery are fundamental to study hearing loss and to design new therapies. Subjects and Methods: Four experimental groups of six Wistar rats with different methods of drug administration were used: (1) injection of subcutaneous kanamycin (400 mg/kg) and intravenous furosemide (100 mg/kg); (2) local application of a sponge soaked in saline close to the round window; (3) animals for which the sponge was soaked in a solution containing kanamycin (200 mg/mL) and furosemide (50 mg/mL); and (4) sham-operated rats. The tympanic bulla was exposed using a ventral approach, and a bullostomy was performed to visualize the round window membrane. Cochlear function was assessed by measuring the auditory brainstem response, and hearing thresholds in response to click and tone burst stimuli were determined as peak and interpeak latencies. At the end of the study, cochlear histology was analyzed. Results: Systemic administration of kanamycin and furosemide induced profound hearing loss and severe hair cell damage. Local delivery of these ototoxic drugs caused comparable damage but avoided the systemic side effects of the drug. Sham-operated and saline control animals did not experience functional alterations. Conclusion: Situating a sponge soaked in kanamycin and furosemide on the round window membrane through the ventral approach is a reliable method to provoke local ototoxicity in rats.

Lower ototoxicity and absence of hidden hearing loss point to gentamicin C1a and apramycin as promising antibiotics for clinical use

“…With the administration method used here, all 45 AG-treated animals survived. These observations confirm the advantage of local round window application in terms of a safe treatment, as it provides an animal model of AG-induced hearing loss with low mortality rates 27,28 .…”

Swept-sine noise-induced damage as a hearing loss model for preclinical assays

“…Briefly, the tympanic bulla was exposed via ventral surgical approach, and a bullostomy was performed at the posterolateral aspect using a small hook. Once the round window and stapedial artery were clearly visible, we applied directly 10 µl of a concentrated (40 mg/ml) P17 or P144 solution or saline ( n = 6 each) to the round window using a gelatin sponge vehicle (Murillo-Cuesta et al, 2009 ).…”

A comparative study of age-related hearing loss in wild type and insulin-like growth factor I deficient mice

“…Paraffin sections (10 μm) or cryosections (20 μm) of temporal bones from Igf1 +/+ and Igf1 −/− mice were processed for Nissl staining, hematoxylin/eosin or other techniques to study their cytoarchitecture. Serial sections were collected to detect the Na + K + -ATPase β2 isoform (rabbit anti-NaK-ATPase, Upstate Biotechnology, dilution 1:200) and Kir4.1 (rabbit anti-KCNJ10, Chemicon International, dilution 1:200), and phalloidin histochemistry was also performed (Alexa-488 conjugated phalloidin, Molecular Probes, Invitrogen, Carlsbad, CA, USA, dilution 1:100: Murillo-Cuesta et al, 2009, 2010a, 2010b; Sanchez-Calderon et al, 2010). For immunohistochemistry, paraffin sections were processed by the avidin-biotin-peroxidase (ABC) method using 3,3-DAB as chromogen.…”