Effects of N-methyl-D-aspartate on the cochlear potentials / 第二军医大学学报

ABSTRACT

Objective: To investigate the effect of N methyl D aspartate(NMDA) on cochlear potentials and to find out the possible neurotoxic effect of NMDA on cochlea function in guinea pigs. Methods: After basal compound action potentials (CAP) and cochlear microphonics (CM) were recorded by round window electrode, animals ( n =5) were treated with Hanks applied to the round window membrane (RWM) for 20 min as control. Then 100 ?mol/L NMDA was applied to the RWM for another 20 min. Results: Hanks produced no obvious changes in CAP threshold, CAP N1 and CM latency and amplitude. CAP thresholds at all frequencies of tone burst were significantly elevated by application of NMDA, threshold shifts ranged from 13 27 dB. NMDA significantly reduced the CAP N1 amplitudes at all intensities of stimulations. CAP amplitudes were suppressed by 50% 75%. NMDA also significantly increased the CAP latency, the latency of CAP evoked by 6 kHz tone burst at intensity of -90 dB(output attenuation) was (1.9?0.06) ms after Hanks treatment and (2.76?0.21) ms after NMDA treatment ( P