title: Toluene effect on the olivocochlear reflex.
abstract: Animal studies have shown that toluene can cause hearing loss and can exacerbate the effects of noise by inhibiting the middle ear acoustic reflex. In this investigation, carried out in Long-Evans rats, the tensor tympani tendon was cutoff and the stapedius muscle was electrocoagulated in one or both middle ears. Rat hearing was evaluated by measuring cubic distortion otoacoustic emissions (2f1-f2; f1 = 8000 Hz; f2 = 9600 Hz; f1/f2 = 1.2) prior to, during, and after activation of the olivocochlear (OC) reflex. A band noise centered at 4 kHz was used as suppressor noise. It was delivered contralaterally to decrease 2f1-f2 amplitude. The strength of the inner ear acoustic reflex was tested by increasing contralateral noise intensity, and toluene injected into the carotid artery was used to study physiological efficacy. Results showed that the protective effect of the OC reflex is intensity dependent. In addition, the OC reflex was found to be less sensitive to toluene than the middle ear acoustic reflex. This may be because the efferent neurons involved in inner ear and middle ear reflexes are located differently. In conclusion, the synergistic effects on hearing of co-exposure to noise and aromatic solvents are because of solvents depressing the central nuclei, which mainly drive the middle ear acoustic reflex.
authors.affiliation: Polluants et Santé Department, Institut National de Recherche et de Sécurité, Rue du Morvan, CS 60027, 54519 Vandœuvre Cédex, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Rumeau
authors.forename: Pierre
authors.initials: P
authors.lastname: Campo
authors.forename: Thomas
authors.initials: T
authors.lastname: Venet
authors.forename: Aurélie
authors.initials: A
authors.lastname: Thomas
authors.forename: Chantal
authors.initials: C
authors.lastname: Cour
authors.forename: Cécile
authors.initials: C
authors.lastname: Parietti-Winkler
mesh_terms: D000818:Animals; D003051:Cochlea / Q000187:drug effects* / Q000503:physiopathology; D034381:Hearing Loss / Q000139:chemically induced* / Q000503:physiopathology; D051381:Rats; D020318:Rats, Long-Evans; D012018:Reflex / Q000187:drug effects*; D014050:Toluene / Q000633:toxicity*
chemical_list: D014050:Toluene