Time course of compensatory mechanisms after GSM-modulated 900 MHz radiation on cerebral activity using a picrotoxin-model in rats

This study investigated the effects of mobile-phone-type radiation on the cerebral activity of seizure-prone animals. The experimental set-up used in this research for exposure of small animals to radiofrequency standing waves allows direct measurement of the power absorbed by the animal. Essentially, the setup consists of a metallic box containing an antenna and experimental animal immobilized in a methacrylate holder; a signal generator feeding the antenna; and a power meter. In addition, the box can also contain a video camera to record the animal´s behavior, and a receiving antenna (connected externally to a power meter and a spectrum analyser) to detect undesired (external) radiation and possible harmonics of the radiating system. The absorbed power measurement trivially allows calculation of whole-body mean SAR from the animal´s weight; an assuming local SARs to be proportional to whole-body mean SAR, the latter can be used to adjust organ-specific SAR predictions obtained by simulation using a commercial FDTD program with a numerical phantom. In an experiment the rats were transformed into an experimental model of seizure-proneness by acute subconvulsive doses of picrotoxin were exposed to 2 hours GSM-modulated 900MHz radiation at intensity similar to that emitted by mobile phones. In this study we analyzed -by means of immunochemical testing of relevant anatomical areas- the relationship between the induction of c-fos (neuronal marker) and GFAP (glia marker) in acute experimentally models to establish the effects on the CNS (Central Nervous System) of 72 adult male Sprague-Dawley rats after 60 minutes, 24 hours and 3 days of exposure to EMF radiation. The parameters of radiation absorbed power, incident power, for the calculus of average SAR_exp, Peak SAR values calculated for picrotoxin-treated and untreated irradiated rats showed non thermal values. The significance of between-group differences in c-fos positive cell counts was assessed by ANOV- - A: a) considering all brain regions together, with factors Treatment (picrotoxin, or no picrotoxin) and Radiation (no radiation, modulated radiation) and Time (90 min, 1 day, 3 days); b) considering each brain region separately, with factors Treatment, Radiation, Area and Time (i.e. areas within that region); and c) considering each brain area separately, with factors Treatment and Radiation and Time. Similar studies were carried out for GFAP positive cells but only at time =3 days. Natural logarithm transformations were applied to data to obtain normality and homoscedasticity. Differences between regions and areas were considered significant at P<;0.05. Tukey HSD test was used in a posteriori comparisons. The results of counting c-fos nucleus showed that the interaction time x radiation was significant, globally, in all regions, and in seven anatomical areas studied (p<;0.001 in all cases). The interaction treatment x time was significant (p<;0.001) except in Entorhinal area (p= 0.053). However, the interaction radiation x treatment was significant (p<;0.02), except in parietal area (p=0.164), in Dentate Gyrus (p=0.753), and in CAj (p=0.091). In the analyses of the GFAP, treatment showed an important effect globally, and also in the seven anatomical areas considered (p<; 0.001). The radiation effect was significant in frontal or CA₃ areas (p<; 0.001, p= 0.016), but not in remaining areas. The treatment-by-radiation interaction was significant globally and in the entorhinal area (p<;=0.001). These results showed that the compensatory mechanism of radiation in brain tissues depends on the time in every neuronal expression of c-fos. But the glia population had a limited response in several areas or regions for same level of radiation.