Impairment of long-term potentiation induction is essential for the disruption of spatial memory after microwave exposure

Abstract

Purpose: To assess the impact of microwave exposure on learning and memory and to explore the underlying mechanisms.

Materials and methods: 100 Wistar rats were exposed to a 2.856 GHz pulsed microwave field at average power densities of 0 mW/cm², 5 mW/cm², 10 mW/cm² and 50 mW/cm² for 6 min. The spatial memory was assessed by the Morris Water Maze (MWM) task. An in vivo study was conducted soon after microwave exposure to evaluate the changes of population spike (PS) amplitudes of long-term potentiation (LTP) in the medial perforant path (MPP)-dentate gyrus (DG) pathway. The structure of the hippocampus was observed by the light microscopy and the transmission electron microscopy (TEM) at 7 d after microwave exposure.

Results: Our results showed that the rats exposed in 10 mW/cm² and 50 mW/cm² microwave displayed significant deficits in spatial learning and memory at 6 h, 1 d and 3 d after exposure. Decreased PS amplitudes were also found after 10 mW/cm² and 50 mW/cm² microwave exposure. In addition, varying degrees of degeneration of hippocampal neurons, decreased synaptic vesicles and blurred synaptic clefts were observed in the rats exposed in 10 mW/cm² and 50 mW/cm² microwave. Compared with the sham group, the rats exposed in 5 mW/cm² microwave showed no difference in the above experiments.

Conclusions: This study suggested that impairment of LTP induction and the damages of hippocampal structure, especially changes of synapses, might contribute to cognitive impairment after microwave exposure.