The effects of antioxidant, chloroquine and noise exposure on auditory brainstem response threshold and distortion product otoacoustic emission amplitude in guinea pigs

The purpose of this study was to evaluate if an antioxidant (U74389G) has a protective effect against the combined ototoxicity of exposure to noise and chloroquine. Fifty-six pigmented guinea pigs were divided into eight groups. Groups were treated with the following: 1 ml subcutaneous injection of chloroquine diphosphate in saline (35 mg/kg), a .3 ml oral solution of antioxidant U74389G in citrate NaCl, or exposed to 93 dB SPL of broadband noise for 48 hours, other groups served as controls. The treatments were administered in the following manner: once daily chloroquine subcutaneous injection for five consecutive days, antioxidant given orally two times per day for three days and noise exposure began on the second day of the antioxidant treatment and continued for 48 hours. Baseline auditory brainstem response (ABR) to tone bursts at 4, 8, 12 & 16 kHz and clicks and distortion product otoacoustic emissions (DPOAE) at 4 and 8 kHz were recorded at three periods. The first was baseline, which occurred prior to exposure to any of the factors. The second measurement (post-treatment) was taken at the end of the 48 hours of noise exposure and the third measurement (recovery) was taken 48 hours after the end of the noise exposure. The ABR measurements indicated that chloroquine appeared to create some hearing loss that was greater in the higher frequencies. The antioxidant appeared to have a protective effect against the combined ototoxic effects of chloroquine and noise exposure. In the antioxidant and noise exposure condition the antioxidant did not decrease the amount of the threshold shift but it appeared to aid in the recovery from noise exposure. The DPOAE measurement also indicated that chloroquine caused hearing loss and that the antioxidant was protective against chloroquine and noise exposure.