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.

Treatment of acoustic trauma.

The aim of this study is to determine the actual efficiency of the present medical treatments of acoustic trauma. Untreated and treated groups of guinea pigs are exposed to a traumatic noise exposure, inducing up to 60-dB threshold shift. The recovery is followed for up to 14 days.

Surgical anatomy of the ear of the fat sand rat.

Objective: This study was conducted to investigate and describe the anatomical details of the ear of the fat sand rat (Psammomys obesus).

Methods: Thirty ears (15 in dry skull and 15 in live animals) were dissected with the aid of an operating microscope and microsurgical techniques. Photographs were taken through an operating microscope.

Effect of long-term noise exposure on the developing and developed ear in the Rat.

There have been reports that the developing ear is more sensitive than the adult ear to noise-induced hearing loss. This was investigated by testing auditory function in rats, both electrophysiologically and histologically, following exposure to broad-band noise (12 h/day for 15 days) at different stages of auditory development (neonates and adults), and also in age-matched controls. An exposure of 90 dB SPL broad-band noise caused no long-term change in auditory function in either age group.

Thyroxine affects physiological and morphological development of the ear.

The onset and development of distortion product otoacoustic emissions (DPE) representing cochlear amplifier activity were studied in neonatal hyperthyroid (n = 10) and control (n = 10) rat pups. These were compared to the onset and development of auditory nerve-brainstem evoked responses (ABR) representing overall cochlear function, and to morphological development of the ear. DPEs were recorded at an earlier postnatal age to high (8 kHz) frequencies and progressed to lower (3 kHz) frequencies with age.