Alterations of cognitive function and 5-HT system in rats after long term microwave exposure

• Published in: Physiology & behavior 2015-03, Vol.140, p.236-246
• Main Authors: Li, Hai-Juan, Peng, Rui-Yun, Wang, Chang-Zhen, Qiao, Si-Mo, Yong, Zou, Gao, Ya-Bing, Xu, Xin-Ping, Wang, Shao-Xia, Dong, Ji, Zuo, Hong-Yan, Li, Zhao, Zhou, Hong-Mei, Wang, Li-Feng, Hu, Xiang-Jun
• Format: Article
• Language: English
• Subjects: 5-HT receptor; Animals; Brain - metabolism; Brain - pathology; Brain - radiation effects; Brain Waves - radiation effects; Cognition Disorders - etiology; Dose-Response Relationship, Radiation; Electroencephalography; Electromagnetic radiation; Hippocampus; Learning and memory; Male; Maze Learning - radiation effects; Microwave; Microwaves - adverse effects; Nerve Degeneration - etiology; Neurotransmitter Agents - metabolism; Neurotransmitters; Psychiatry; Rats; Rats, Wistar; Reaction Time - radiation effects; Receptors, Serotonin - genetics; Receptors, Serotonin - metabolism; Serotonin; Serotonin - metabolism; Swimming - psychology; Time; Time Factors; Tryptophan Hydroxylase - metabolism
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2014.12.039

Abstract The increased use of microwaves raises concerns about its impact on health including cognitive function in which neurotransmitter system plays an important role. In this study, we focused on the serotonin system and evaluated the long term effects of chronic microwave radiation on cognition and correlated items. Wistar rats were exposed or sham exposed to 2.856 GHz microwaves with the average power density of 5, 10, 20 or 30 mW/cm2 respectively for 6 min three times a week up to 6 weeks. At different time points after the last exposure, spatial learning and memory function, morphology structure of the hippocampus, electroencephalogram (EEG) and neurotransmitter content (amino acid and monoamine) of rats were tested. Above results raised our interest in serotonin system. Tryptophan hydroxylase 1 (TPH1) and monoamine oxidase (MAO), two important rate-limiting enzymes in serotonin synthesis and metabolic process respectively, were detected. Expressions of serotonin receptors including 5-HT1A, 2A, 2C receptors were measured. We demonstrated that chronic exposure to microwave (2.856 GHz, with the average power density of 5, 10, 20 and 30 mW/cm2 ) could induce dose-dependent deficit of spatial learning and memory in rats accompanied with inhibition of brain electrical activity, the degeneration of hippocampus neurons, and the disturbance of neurotransmitters, among which the increase of 5-HT occurred as the main long-term change that the decrease of its metabolism partly contributed to. Besides, the variations of 5-HT1A R and 5-HT2C R expressions were also indicated. The results suggested that in the long-term way, chronic microwave exposure could induce cognitive deficit and 5-HT system may be involved in it.