Preventing noise induced otoacoustic emission loss by increasing magnesium (Mg2+) intake in guinea-pigs.

This study aimed to explore the effects of increased Mg2+ intake on the activity of the outer hair cells as manifested in Click and Distortion Evoked Otoacoustic Emissions (CEOAEs; DPOAEs) in 25 animals. Thirteen animals were fed with high Mg2+ intake (39 mmol Mg2+/l in drinking water) and 12 without the Mg2+ additive. The OAE amplitudes and frequency ranges as well as the DPOAE thresholds were affected significantly less by noise exposure in the animals fed Mg2+-enriched water.

Therapeutic efficacy of magnesium in acoustic trauma in the guinea pig.

Comparative functional and morphological tests were performed in two groups of impulse noise-exposed guinea pigs treated either with magnesium (Mg) or isotonic saline as a placebo to extend the knowledge on the therapeutic efficacy of Mg in acoustic trauma demonstrated recently. The permanent threshold shifts were significantly lower in the Mg than in the placebo group as measured by auditory brainstem response audiometry, distortion product otoacoustic emissions and compound action potentials (CAPs) 1 week after exposure. This also applies to the damage to hair cell stereocilia tested with scanning electron microscopy.

Therapeutic effect of magnesium on noise-induced hearing loss.

This study examined the therapeutic effect of magnesium (Mg) on noise trauma in anesthetized guinea pigs exposed to an impulse noise series (1/s) of Lpeak 167 dB (Leq,1s 127 dB) for 38 min. The permanent hearing threshold shift (PTS) was measured 1 week post-exposure, using auditory brain stem response audiometry (frequency range, 0.5-32 kHz).

Therapeutic effect of parenteral magnesium on noise-induced hearing loss in the guinea pig.

We have recently demonstrated in the guinea pig that preventive dietary magnesium supplement can significantly reduce impulse noise induced hearing loss by on average 18 dB. The purpose of the present study was to examine whether magnesium might also have a therapeutic effect on noise trauma. Anesthetized guinea pigs were exposed to an impulse noise series (1/s) of L(peak) 167 dB (L(eq,ls) 127 dB) for 38 min.

Preventive magnesium supplement protects the inner ear against noise-induced impairment of blood flow and oxygenation in the guinea pig.

We have recently demonstrated in the guinea pig that preventive dietary magnesium supplement can significantly reduce hearing loss caused by acute impulse noise exposure. To elucidate the underlying protective mechanisms of magnesium, the present study examined its effect on noise-induced impairment of cochlear blood flow (CoBF) and perilymphatic oxygen partial pressure (pO2) in two groups of guinea pigs maintained on optimal or suboptimal dietary magnesium status. While laser Doppler flowmetry was used to determine CoBF, perilymphatic pO2 was measured polarographically using micro-coaxial platinum needle electrodes.