Effects of Mobile Phone Radiation upon the Mammalian Brain

Sammanfattning: oday about half of the world's population owns the microwave producing mobile phones. The blood-brain barrier (BBB) protects the mammalian brain from potentially harmful substances circulating in the blood. The permeability of the BBB has been shown to be increased after exposure to electromagnetic fields (EMFs) of the kind emitted by mobile phones and neuronal damage has been found several weeks after the exposure. The aim of this thesis was to further investigate the effects of exposure to global system for mobile communications (GSM) radiation upon the rat brain. In Paper I, rats were exposed to GSM radiation for two hours, followed by a seven-day recovery period after which the animals were sacrificed. The GSM exposed rats had a significantly increased BBB permeability as compared to the sham exposed control rats, seen as increased amount of albumin extravasation. In Paper II, we examined the effects of long-term exposure of rats for totally 55 weeks, 2 hours weekly, to GSM radiation. After this protracted exposure, an open-field test demonstrated no behavioural changes. On the other hand, the episodic memory was impaired after GSM exposure, as demonstrated in the episodic-like memory test. In Paper III histopathological light microscopial examinations of the long-term GSM exposed animals were presented. Albumin extravasation, neuronal damage and signs of accelerated ageing were investigated. No significant difference between the GSM exposed and sham control rats was seen. In Paper IV, microarray analysis of the gene expression in cortex and hippocampus of mobile phone exposed rats was performed. 31, 099 rat genes, including splicing variants, were analyzed. At the single gene level, no statistically significant alterations could be seen. However, with Gene Ontology (GO) analysis, 25 predefined GO categories had significantly altered gene expression in cortex and 20 GO categories had significantly altered gene expression in hippocampus. Four GO categories were among the ten most significantly altered groups in both cortex and hippocampus after GSM exposure; that is, extracellular region, signal transducer activity, intrinsic to membrane and integral to membrane. Considering the vast number of mobile phone users today, the non-thermal effects of mobile phoning and the mechanisms behind them, must indeed continue to be investigated.