Effects of X-band high-power microwave on emotional cognition in mice

Background Current studies have found that low-frequency electromagnetic radiation can cause changes in emotional and cognitive functions, but the effects of X-Band HPM on emotional cognition and their molecular mechanisms remain unclear. Objective To investigate the effects of X-band high power microwave on emotion and cognition in mice and the underlying mechanisms.Methods Male C57BL/6 mice aged 8-10 weeks were randomly divided into blank control group, low-dose irradiation group, high-dose irradiation group, with 8-10 mice in each group. The control group received no irradiation, while the irradiation groups were exposed to X-Band HPM as the radiation source (emission frequency: 9.4 GHz, pulse width: 100 ns, pulse repetition frequency: 30 Hz). The low-dose group had a peak power density of 26 W/cm² and an average power density of 0.078 mW/cm², whereas the high-dose group had a peak power density of 1 750 W/cm² and an average power density of 5.25 mW/cm². Each mouse was individually irradiated. After irradiation, the open field test, elevated plus maze test, and tail suspension test were  used to evaluate changes in emotional behavior, while the novel object recognition test was applied to assess cognitive behavioral changes. The morphological structure of hippocampal tissue was observed by HE staining and TUNEL staining, and the ultrastructure of the DG region in the hippocampus was observed by TEM. The neurotransmitter content in hippocampal tissue was detected by ultra-high performance liquid chromatography-mass spectrometry. The expression levels of PSD95 and BDNF in hippocampal tissue were detected by WB.Results In the open-field test, the distance and time spent in the central area, as well as the total distance traveled, were significantly lower in both high-dose and low-dose groups compared to the control group (P<0.05). In the elevated plus-maze test, the number of entries into open arms and the residence time in the high-dose group, as well as the residence time in the low-dose group, were significantly reduced (P<0.01). In the tail suspension test, the immobility time was significantly prolonged in the high-dose group (P<0.01). In the novel object recognition test, the cognitive indices of both high-dose and low-dose groups were significantly lower than those of the control group (P<0.01). HE staining and TUNEL staining results showed that in the high-dose irradiation group, partial neuronal shrinkage was observed, with irregular cell shapes, reduced cell volume, unclear boundaries between nucleus and cytoplasm, deepened staining, irregular cell arrangement, decreased compactness of cell arrangement, and local gaps. Transmission electron microscopy results indicated that synapses and mitochondria were partially damaged in the low-dose group, while other structures were in acceptable condition; in the high-dose group, synaptic structures, neurotransmitter vesicles, mitochondria, etc., were damaged to varying degrees. Neurotransmitter detection showed that compared with the blank control group, the contents of γ-GABA, Gln, Pro, cystathionine, and L-carnosine in the hippocampal tissue of mice in the high-dose irradiation group were significantly reduced (P<0.05), while the contents of Glu and Orn were significantly increased (P<0.05). In the low-dose irradiation group, the content of cystathionine was significantly lower than that of the control group (P<0.01), while the contents of γ -GABA, L-AA, Abu, Hyl, and Aib were significantly higher (P<0.05). WB results demonstrated that the expression levels of PSD95 and BDNF in hippocampal tissue were significantly decreased (P<0.01). Conclusion X-Band HPM can induce anxiety, depression, and cognitive dysfunction in mice, and the mechanism may be related to impaired hippocampal synaptic structural integrity, decreased plasticity, and dysregulation of related neurotransmitter secretion.