Effects of long-term microwave irradiation on NMDAR, BDNF and related molecular expression in their signal pathways in rat hippocampus

Objective: To evaluate the effect of long-term microwave radiation on the expression of N-methyl-D-aspartate receptor (NMDAR), brain derived neurotrophic factor (BDNF) and related molecules in signal pathways in the hippocampus of rats. Methods: Fifty male Wistar rats were exposed to microwave radiation at an average power density of 0, 5, 10, 20 and 30 mW/cm² for 6 min/ time, 3 times/week, and for 6 weeks, which were sacrificed and the hippocampus was quickly removed at 14 d and 28 d after exposure. The changes in NMDAR (NR1, NR2A, NR2B), postsynaptic density protein (PSD)-95, cortactin, BDNF and tyrosine kinase receptor B (TrkB) in hippocampal neurons of each group were detected by Western blotting and image analysis techniques. Results: Compared with the control group, the expressions of related proteins did not change significantly after microwave irradiation of 5 mW/cm² at each time point. After 20 mW/cm² microwave radiation, the expression of NRI was increased at 14 and 28 d (P < 0.05), the expression of NR2A was increased at 28 d (P < 0.05), but the expression of NR2B was decreased at 14 and 28 d (P < 0.05). At a average power density of 30 mW/cm², the expressions of NR1, NR2A and PSD-95 and the expression of NR2B were decreased at 14 and 28 d (P < 0.05), and cortactin, BDNF and TrkB were increased at 14 d after irradiation (P < 0.05). Conclusion: The effect of different dosages of long-term microwave radiation on the proteins of NMDAR and its signal pathway related molecules is different. Microwave radiation may affect the NMDAR of postsynaptic information transmission through the BDNF-TrkB signaling pathways, which might play an important role in the impediment of learning and memory function caused by microwave radiation. (authors)