OBJECTIVEImpulse noise was adopted in adult rats to built acute deafferent animal model. Differential proteomics techniques were applied to detect the changes of protein expression in the auditory cortex before and after the noise exposure.

METHODSThirty adult SD rats were divided into three groups: normal group, rats with acute noise exposure and rats 28 days recovery after noise exposure (n=10/group). All animals were exposed to impulse noise at 156 dB for 50 pulses with a rise-time of 100 µs and duration of around 0.25 ms. ABR was used to evaluate the auditory function. The two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS) were used to identified the differential protein expression.

RESULTSCompared with the normal group, ABR thresholds were found significantly increased at 2, 4, 8, 16, 32 kHz (P<0.05) in the acute and recovery groups. There was a 40-60 dBSPL ABR threshold shift at all tested frequencies immediately after impulse noise exposure. There was a partial recovery of ABR thresholds at 7 day to 28 days after impulse noise exposure. In addition, it seemed that the thresholds were rather stable and no further ABR threshold recovery was observed from 14 day to 28 days after the impulse noise exposure. Using differential proteomic techniques, 36 spots containing 27 proteins were revealed and identified in auditory cortex. Those proteins are related to cytoskeleton, neurotransmission, energy supply, mitochondrial function and synaptic remolding.

CONCLUSIONSImpulse noise may influence the function of microtubule transport and cell metabolism, there after affect the neurotransmission of auditory neurons. The compensatory changes such as pre- and postsynaptic or such related functional changes may also happen in auditory cortex after the deafferentation treatment.