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Etude des effets d'une co-exposition au bruit et aux solvants aromatiques sur l'audition : mécanismes périphériques et centraux

Abstract : Combined exposure to noise and toluene has more harmful auditory effects than the sum of those caused by each factor. The goal of this thesis was to study the peripheral and central mechanisms responsible for the synergy between the effects of the solvent and those induced by noise. Since the outer hair cells are the sensitive targets of solvents, the cochlear microphonic potential (CMP) was used to monitor the electrical activity of these cells on rats exposed to both noise and toluene. The intra-carotidial injection of a bolus of intralipid containing toluene provoked a transient increase in CMP magnitude (~9 dB SPL) triggered by a 85-dB SPL ipsi-lateral noise. Given that the CMP increase was dependent on the intensity of the acoustic stimulation, it was reasonable to think that the nervous center of the acoustic reflexes, the brainstem, might have been targeted by the solvent. This assumption was confirmed by investigations performed with rats whose acoustic reflexes had been triggered with a contra-lateral noise. While triggering the reflexes caused a CMP decrease, the toluene injection inhibited the effects of the acoustic reflexes, and more precisely those of the middle ear reflex (MER). In addition, injections of antagonists of cholinergic receptors provoked increases in CMP similar to those generated by toluene. Toluene may therefore inhibit the cholinergic receptors of the efferent pathways involved in the MER. The MER inhibitory could explain the synergy of the effects of combined exposure to noise and solvents
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Katy Maguin. Etude des effets d'une co-exposition au bruit et aux solvants aromatiques sur l'audition : mécanismes périphériques et centraux. Biologie cellulaire. Université Henri Poincaré - Nancy 1, 2008. Français. ⟨NNT : 2008NAN10126⟩. ⟨tel-01748383⟩

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