Toluene ototoxicity in rats: assessment of the frequency of hearing deficit by electrocochleography.
To identify the frequency range most sensitive to toluene-induced auditory damage, the auditory function of adult Long-Evans rats exposed to 1750 ppm of toluene (6 h/day, 5 days/week, 4 weeks), was tested by recording auditory-evoked potentials directly from the round window of the cochlea. The present electrocochleographic findings do not support a specific mid- to high-frequency loss of auditory sensitivity. On the contrary, the electrophysiologic data, obtained for audiometric frequencies ranging from 2 to 32 kHz, showed a hearing deficit not only in the mid-frequency region (12-16 kHz), but also in the mid-low-frequency region (3-4 kHz). Actually, the effect of toluene was independent of the frequency in our experimental conditions. Histological analysis was consistent with electrophysiologic data because a broad loss of outer hair cells occurred in both mid- and mid-apical coil of the organ of Corti.
Lataye
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R
Institut National de Recherche et de Sécurité, Vandoeuvre, France. campo@inrs.fr
Campo
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P
Loquet
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G
D000818:Animals; D001299:Audiometry; D001300:Audiometry, Evoked Response; D003051:Cochlea / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000187:drug effects*; D006309:Hearing / Q000187:drug effects* / Q000502:physiology; D006311:Hearing Disorders / Q000139:chemically induced* / Q000503:physiopathology*; D008297:Male; D008855:Microscopy, Electron, Scanning; D009925:Organ of Corti / Q000187:drug effects / Q000648:ultrastructure; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000187:drug effects; D014050:Toluene / Q000633:toxicity*
D014050:Toluene