Effect of electromagnetic field exposure on the structure and function of the primary auditory cortex in mice

Objective To explore the effect of static magnetic field and microwave combined exposure on the structure and function of primary auditory cortex in mice，and to provide new ideas for the study of biological effect mechanisms and protection of electromagnetic field composite exposure.Methods C57BL/6N mice were selected and exposed to static magnetic field exposure simulation source and microwave radiation simulation source built by the Academy of Militray Medical Sciences. Firstly，they were exposed to static magnetic field of 100mT for 1h，and then exposed to microwave radiation with center frequency of 9.875 GHz and SAR value of 2.58 W/Kg for 15min to establish and animal model of electromagnetic field composite exposure.The effects of composite exposure to electromagnetic fields on auditory neurobehavior were studied by Startle Reflex of prepulse inhibition (PPI) experiment. Auditory brainstem response (ABR) and distortion product otoacoustic emission(DPOAE) were used to study the effects of composite exposure to electromagnetic field on auditory electrophysiological function.The effects of composite exposure to electromagnetic field on the morphology and ultrastructure of primary auditory cortex were observed by light microscopy and transmission electron microscopy.Results 3, 14, 28 d after exposure to electromagnetic field，the composite exposure group of the percentage of PPI was significantly higher than before exposure and in the single static magnetic field or microwave exposure group (P＜0.05)；7, 14, 28 d after exposure to electromagnetic field，the latency of ABR I wave was significantly increased (P＜0.05) compared with the control group and the single static magnetic field or microwave radiation exposure group，while the amplitude of DPOAE was significantly decreased (P＜0.05)；ABR threshold didn’t change significantly. 7 d after exposure to electromagnetic field，some neurons showed degeneration and apoptosis，blurred synaptic cleft，and swelling of glial mitochondria in the primary auditory cortex，which was most obvious in the composite exposure group.Conclusions The composite exposure of static magnetic field and microwave can lead to impaired function of cochlear outer hair cells, inhibited function of cochlear nerve uplink conduction pathway, histologic pathology changes of primary auditory cortex and abnormal sensorimotor gating function, but has no effect on hearing threshold.