Early exposure to radiofrequency electromagnetic fields at 1850 MHz affects auditory circuits in early postnatal mice

Ju Hwan Kim,Seung Cheol Ahn,Yang Hoon Huh,Jae Yun Jung,Jae-Hun Lee,Hak Rim Kim

doi:10.1038/s41598-018-36868-1

Ju Hwan Kim, Seung Cheol Ahn + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-36868-1

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Abstract

In the present study, we measured the spontaneous post synaptic currents (sPSCs) at the post synaptic principle cells of the medial nucleus of the trapezoid body (MNTB) in early postnatal mice after exposure to 1850 MHz radiofrequency electromagnetic fields (RF-EMF). sPSC frequencies and amplitudes were significantly increased in the RF-EMF exposed group. Moreover, the number of synaptic vesicles in the calyx of Held was significantly increased in presynaptic nerve terminals. Following RF-EMF exposure, the number of docking synaptic vesicles in the active zone increased, thereby expanding the total length of the presynaptic active zone in the calyx of Held. These data suggest that the increased sPSCs are a result of greater synaptic vesicle release from presynaptic nerves. However, we found no morphological changes in the inner hair cell ribbon synapses. Further, there were no significant changes in the hearing threshold of the auditory brainstem response at postnatal day 15. Our results indicate that exposure to RF-EMF at an early postnatal stage might directly affect brainstem auditory circuits, but it does not seem to alter general sound perception.

Highlights

With the widespread adoption of wireless communication devices in recent decades, there has been a growing public interest in the various biological effects of radiofrequency (RF) electromagnetic fields (EMFs) emitted by mobile phones
To evaluate how radiofrequency electromagnetic fields (RF-EMF) regulate synaptic transmission of medial nucleus of the trapezoid body (MNTB) synapses, spontaneous post synaptic currents (sPSCs) were recorded at post synaptic cells of the MNTB using the whole cell voltage clamp technique
We found that 1850 MHz RF-EMF exposure increases the frequency and amplitude of sPSCs at post synaptic cells of the MNTB

Summary

Introduction

With the widespread adoption of wireless communication devices in recent decades, there has been a growing public interest in the various biological effects of radiofrequency (RF) electromagnetic fields (EMFs) emitted by mobile phones. Sun et al.[12] reported that exposure to extremely low frequency electromagnetic field (ELF-EMF) at the early postnatal period could facilitate endocytosis and post-tetanic potentiation. This was possibly mediated via enhanced expression of P/Q subtype calcium channels in the medial nucleus of the trapezoid body (MNTB), which is one of the main auditory circuit nuclei in the brainstem[12]. Another study reported an effect of EMF exposure on neural differentiation and outgrowth at the embryonic period[13] These findings about the cellular changes in response to EMF exposure motivated our research into its possible effect on spontaneous post synaptic currents (sPSCs). Any possible physiological or morphological changes in MNTB neurons were studied using histological analyses of the ribbon synapse in the inner hair cells and by determining the hearing threshold using the auditory brainstem response

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