title: Long-term administration of magnesium after acoustic trauma caused by gunshot noise in guinea pigs.
abstract: In a previous study we observed that a 7-day post-trauma magnesium treatment significantly reduced auditory threshold shifts measured 7 days after gunshot noise exposure. However this improvement was only temporary, suggesting that it could be potentially beneficial to prolong this treatment. The aim of the present study was to evaluate the efficacy of a long-term (1 month) magnesium treatment after an impulse noise trauma, in comparison with either a 7-day magnesium treatment, an administration of methylprednisolone (conventional treatment), or a placebo (NaCl). Guinea pigs were exposed to impulse noise (three blank gunshots, 170 dB SPL peak). They received one of the four treatments, 1 h after the noise exposure. Auditory function was explored by recording the auditory brainstem response (ABR) and measuring the distortion product otoacoustic emissions (DPOAE) over a 3-month recovery period after the gunshot exposure. The functional hearing study was supplemented by a histological analysis. The results showed that a 1-month treatment with magnesium was the most effective treatment in terms of hair cell preservation. The DPOAE confirmed this effectiveness. Methylprednisolone accelerated recovery but its final efficacy remained moderate. It is probable that magnesium acts on the later metabolic processes that occur after noise exposure. Multiple mechanisms could be involved: calcium antagonism, anti-ischaemic effect or NMDA channel blockage. Regardless of the specific mechanism, a 1-month treatment with magnesium clearly attenuates NIHL, and presents the advantage of being safe for use in humans.
authors.affiliation: Centre de recherches du service de santé des armées, Radiobiologie, 24 avenue des Maquis du Grésivaudan, BP 87, 38702 La Tronche, France. L.abaamrane@crssa.net
authors.forename: L
authors.initials: L
authors.lastname: Abaamrane
authors.forename: F
authors.initials: F
authors.lastname: Raffin
authors.forename: M
authors.initials: M
authors.lastname: Gal
authors.forename: P
authors.initials: P
authors.lastname: Avan
authors.forename: I
authors.initials: I
authors.lastname: Sendowski
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004334:Drug Administration Schedule; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D005389:Firearms; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000473:pathology; D006317:Hearing Loss, Noise-Induced / Q000473:pathology / Q000503:physiopathology*; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D008274:Magnesium / Q000008:administration & dosage*; D008775:Methylprednisolone / Q000008:administration & dosage; D018696:Neuroprotective Agents / Q000008:administration & dosage; D009622:Noise; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects; D010469:Perceptual Distortion; D020127:Recovery of Function / Q000187:drug effects
chemical_list: D018696:Neuroprotective Agents; D008274:Magnesium; D008775:Methylprednisolone