Aminoglycoside antibiotics and the sensory hair cells of inner ear and lateral line system in the Atlantic cod, Gadus morhua: effects on fish hearing threshold

• Main Authors: Faucher, Karine, Aas-Hansen, Øyvind, Damsgard, Borge, Bégout, Marie-Laure, Fuhr, Torgrim, Laukli, Einar, Stenklev, Niels-Christian
• Other Authors: IKM, University of Tromso
• Format: Conference Object
• Language: English
• Published: 2007
• Subjects: hearing threshold; ABR; inner ear; lateral line system; sensory hair cells; cod; Life sciences; Environmental sciences & ecology; Sciences du vivant; Sciences de l’environnement & écologie; atlantic cod; Gadus morhua
• Online Access: https://orbi.uliege.be/handle/2268/40514; https://orbi.uliege.be/bitstream/2268/40514/1/Poster%20Karine%20Faucher.pdf

The aims of the present study were to investigate: a) the potential involvement of the fish lateral line system in hearing at 250 Hz and b) the possible regeneration of the inner ear hair cells in the Atlantic cod (Gadus morhua). The inner ear and lateral line system of the Atlantic cod were inactivated using ototoxic aminoglycoside antibiotics by injection (gentamicin) or bath (gentamicin and streptomycin), respectively. Hearing thresholds were measured in the fish using the Auditory Brainstem Response (ABR) technique at 10, respectively 17 - 20 days following antibiotic treatment. Results were compared between groups of individuals i) with inner ear damage, ii) with lateral line system altered, iii) placebo (immersion in fresh sea water) and iv) control. The sound stimuli applied were series of 2000 five-cycle (2-1-2) 250 Hz tone bursts delivered using a Brüel & Kjær (Nærum, Denmark) loudspeaker. ABRs were measured using a filter set at 30-3000 Hz, a gain of 100 000 and visual interpretation using the Bio-Logic AEP software. Sound stimulus level was reduced until threshold was attained. To check the tissue status of the inner ear and lateral line system, hair cells from sensory maculae were visualized using scanning electron microscope (SEM). Ten days after treatment, hearing thresholds of placebo and lateral line damaged cods did not differ from controls fish (p = 0.387 and p = 0.095, respectively), whereas the fish that received intravenous gentamicin injection had significantly elevated hearing thresholds compared to controls (p < 0.0001). SEM analyses further demonstrated that, 10 days following antibiotic treatment, cod inner ear hair cells were damaged, as well as lateral line hair cells and more particularly in the case of canal neuromasts. There was no hearing effect or microscopic tissue damage in untreated fish. From the 17th day after treatment, ABR measurements showed that some of the gentamicin treated fish had regained hearing thresholds comparable to the control cods (p = 0.535), and this ...