A Characteristic of Aspirin-Induced Hearing Loss in Auditory Brainstem Response of Conscious Rats.

Abstract

ABSTRACT. The acute effects of aspirin on auditory functions were examined electrophysiologically in conscious rats with chronically implanted electrodes for auditory brainstem response (ABR) recording. A single intravenous injection of aspirin at a dose of 225 mg/kg caused a reduction in the amplitude of the ABR P1 wave evoked by a 2 kHz tone pip 1 and 24 hr after dosing at almost all sound intensity levels, while the P1 amplitude at 4 kHz was reduced mainly 1 hr after dosing, and the P1 amplitude at 8 kHz was not significantly affected at middle and high intensities even 1 hr after dosing. The audiogram obtained from the P1 amplitude showed a significant increase in the sound threshold 1 and 24 hr after dosing at 2 kHz, and 1 hr after dosing at 4 kHz, but not at 8 kHz. The peak latency of the P1 wave was also prolonged. Furthermore, reduction of the P2 and P4 wave amplitude and prolongation of the P1-P2 and P2-P4 interpeak latency were also observed at 2 kHz but not at 4 or 8 kHz. These results suggest that the rat auditory function for low frequency is vulnerable to the effects of aspirin. This paradigm, i.e., frequency selectivity, in rats may be useful to further assess the different outer hair cells along the cochlear duct and provide additional evidence for the mechanism(s) or site underlying aspirin ototoxicity. -KEY WORDS: ABR, aspirin, conscious rat, frequency selectivity.J. Vet. Med. Sci. 59(1): 9-15, 1997The mammalian cochlea performs a frequency analysis of airborne sound by processing different frequencies at different portions along the cochlear duct: high frequencies at the base and low frequencies at the apex. It has been reported that the hearing impairment induced by aspirin and salicylates in humans does not depend on the sound frequency [25], but others have claimed that higher frequencies are more susceptible to the effects of these drugs in humans and/or guinea pigs [8,10,22]. Boettcher and Salvi have reported that the results of the effects of aspirin on frequency selectivity are conflicting [3]. Most reports do agree that hearing loss and/or tinnitus are caused by these drugs. In almost all studies, the ototoxicity of aspirin and/or salicylate has been assessed in guinea pigs [8,11,27], monkeys [25,29] or cats [13,14,30], and little information is available on the effects of aspirin on the auditory function of rats. Recently it was indicated in rats that salicylate had a stronger effect on the otoacoustic emission distortion product for high and low frequencies with a clearly smaller effect for frequencies from the range of 6 to 8 kHz, and additionally, the loudness of salicylateinduced rat tinnitus was detected at moderate intensities corresponding to 62 dB SPL below 10 kHz by the behavioral response [18].If aspirin has a different effect at different OHCs along the cochlear duct in rats, aspirin's effect on the frequency selectivity may provide an additional approach to locating the mechanism or site of aspirin's action within the cochlea. In the present study, we examined the effects ...

Frequency Selectivity on Aspirin-Induced Hearing Loss in Rats with Auditory Stimulus-Induced Conditioned Suppression.

“…These results in the present study indicate that a single injection of aspirin causes impairment of auditory function, i.e., hearing loss, and that in rats the function for low sound frequency is vulnerable to the effects of aspirin and hearing was apparently unaffected by this drug at 4, 8 or 10 kHz of the frequencies using to restrict the variation normally found between threshold intensities and frequencies. Upon hearing loss, the above our results of the subjective examination using the rat operant were highly consistent with those of the objective test, which was reported previously by Kurata et al [22], with the auditory brainstem response (ABR) of the rat. However, there were discrepancies in the changes at 4 kHz between the both studies.…”

“…Myers and Bernstein [27] reported that the hearing impairment induced by aspirin and salicylates in human does not depend on the sound frequency, but others have claimed that higher frequency is more susceptible to the effects of these drugs in human and/or guinea pigs [8,11,23]. Contrary to this, we recently reported that the hearing for lower frequency is more susceptible in the rat [22]. Most reports do agree that hearing loss and/or tinnitus are caused by aspirin; however, Boettcher and Salvi [2] reported that the results on the effects of aspirin on frequency selectivity are conflicting.…”

“…In the present study of rats, to verify the results of our previous rat auditory brainstem response study [22], we first applied the conditioned suppression technique and then examined the effects of a single dose of aspirin on auditory stimulus-induced conditioned suppression, paying special attention to frequency selectivity.…”

Alterations in Peripheral and Central Components of the Auditory Brainstem Response: A Neural Assay of Tinnitus

“…While there is a paucity of data regarding ABR tone intensity function shifts or threshold changes immediately following SS-induced hearing loss and tinnitus, considerable research has been performed examining post-SS threshold shifts within specific auditory structures. An earlier study determining threshold changes based on the ABR peak 1 (P1) amplitude found an increase of approximately 12–20 dB SPL (dependent of stimulus frequency) following aspirin administration in rats [ 23 ]. When the compound action potential (CAP), an assessment of cochlear sensitivity, was measured in rats before and after systemic SS treatment, a significant increase in the thresholds at all tested frequencies was observed along with a significant reduction in CAP response amplitude, although the amplitude reduction was least at 16 kHz [ 24 ].…”

The role of PKCζ in amikacin-induced apoptosis in the cochlea: Prevention by aspirin

“…Aspirin is known to induce temporary and reversible thresholds shifts [65]. However, such alterations have been reported for high doses-intravenous injections of 225 mg/kg aspirin or intraperitoneal injections of 300 mg/kg salicylate [66,67]. In our experimental conditions, aspirin alone, supplied at a dose of 10 or 100 mg/kg/day (for comparison, the analgesic dose of aspirin for rats is 100 mg/kg every 4 h) had no toxic effect on hair cells.…”