Carbon disulfide potentiates the effects of impulse noise on the organ of Corti

Autor: Lise Merlen, Monique Chalansonnet, Hervé Nunge, Aurélie Thomas, Jordi Llorens, Thomas Venet, Maria Carreres Pons, Frédéric Cosnier, Pierre Campo
Rok vydání: 2017
Předmět:
Zdroj: NeuroToxicology. 59:79-87
ISSN: 0161-813X
Popis: Occupational noise can damage workers’ hearing, and the phenomenon is even more dangerous when noise is associated with an ototoxic solvent. Aromatic solvents are known to provoke chemical-induced hearing loss, but little is known about the effects on hearing of carbon disulfide (CS 2 ) when combined with noise. Co-exposure to CS 2 and noise may have a harmful effect on hearing, but the mechanisms involved are not well understood. For instance, CS 2 is not thought to have a cochleotoxic effect, but rather it is thought to cause retrocochlear hearing impairment. In other words, CS 2 could have a distal neuropathic effect on the auditory pathway. However, a possible pharmacological effect of CS 2 on the central nervous system (CNS) has never been mentioned in the literature. The aim of this study was to assess, in rats, the effects of a noise (continuous vs. impulse), associated with a low concentration of CS 2 [(short-term threshold limit value) x 10 as a safety factor] on the peripheral auditory receptor. The noise, whatever its nature, was an octave band noise centered at 8 kHz, and the 250-ppm CS 2 exposure lasted 15 min per hour, 6 h per day, for 5 consecutive days. The impact of the different experimental conditions on hearing loss was assessed using distortion product oto-acoustic emissions and histological analyses. Although the LEX,8 h (8-h time-weighted average exposure) for the impulse noise was lower (84 dB SPL) than that for the continuous noise (89 dB SPL), it appeared more damaging to the organ of Corti, in particular to the outer hair cells. CS 2 exposure alone did not have any effect on the organ of Corti, but co-exposure to continuous noise with CS 2 was less damaging than exposure to continuous noise alone. In contrast, the cochleo-traumatic effects of impulse noise were significantly enhanced by co-exposure to CS 2 . Therefore, CS 2 can clearly modulate the middle-ear reflex function. In fact, CS 2 may have two distinct effects: firstly, it has a pharmacological effect on the CNS, modifying the trigger of the acoustic reflex; and secondly, it can make the organ of Corti more susceptible to impulse noise. The pharmacological effects on the CNS and the effects of CS 2 on the organ of Corti are discussed to try to explain the overall effect of the solvent on hearing. Once again, the results reported in this article show that the temporal structure (continuous vs. impulse) of noise should be taken into consideration as a key parameter when establishing hearing conservation regulations.
Databáze: OpenAIRE
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