The relationship between NMDA receptors and microwave-induced learning and memory impairment: A long-term observation on Wistar rats

Abstract

Purpose: To investigate whether high power microwave could cause continuous disorders to learning and memory in Wistar rats and to explore the underlying mechanisms.

Materials and methods: Eighty Wistar rats were exposed to a 2.856 GHz pulsed microwave source at a power density of 0 mW/cm² and 50 mW/cm² microwave for 6 min. The spatial memory ability, the structure of the hippocampus, contents of amino acids neurotransmitters in hippocampus and the expression of N-methyl-D-aspartic acid receptors (NMDAR) subunit 1, 2A and 2B (NR1, NR2A and NR2B) were detected at 1, 3, 6, 9, 12 and 18 months after microwave exposure.

Results: Our results showed that the microwave-exposed rats showed consistent deficiencies in spatial learning and memory. The level of amino acid neurotransmitters also decreased after microwave radiation. The ratio of glutamate (Glu) and gammaaminobutyric acid (GABA) significantly decreased at 6 months. Besides, the hippocampus showed varying degrees of degeneration of neurons, increased postsynaptic density and blurred synaptic clefts in the exposure group. The NR1 and NR2B expression showed a significant decrease, especially the NR2B expression.

Conclusions: This study indicated that the content of amino acids neurotransmitters, the expression of NMDAR subunits and the variation of hippocampal structure might contribute to the long-term cognitive impairment after microwave exposure.

Keywords::

• Microwave
• learning and memory
• NMDAR
• hippocampus
• rats

Acknowledgements

This work was supported by grants from the National Natural Science Foundation of China (General Grant No. 81172620 and No. 61401497).The authors would like to give special thanks to the editor and referees for comments and suggestions that greatly improved the substance and presentation of the paper.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.