TOLUENE-INDUCED HEARING-LOSS - A MID-FREQUENCY LOCATION OF THE COCHLEAR LESIONS

Inhaled toluene (from 1000 to 2000 ppm, 6 h/day, 5 days/week, 4 weeks) is an ototoxic solvent that severely damaged the cochlea in adult Lon g-Evans rats. Auditory function was tested by recording near field pot entials from the inferior colliculus. Surprisingly, the electrophysiol ogic results did not reflect all the cochlear damage observed by histo logy. Loss of outer hair cells of the organ of Corti occurred in all t oluene-treated rats in middle and mid-apical turns, whereas the basal turn of the cochlea was fairly well preserved. The third row of outer hair cells was more injured than the second row, which itself was more injured than the first row. The locations of the cochlear lesions are reported in the present study with regard to the toluene dose. (C) 19 97 Elsevier Science Inc.