Effects of head-only exposure to 900 MHz GSM electromagnetic fields in rats : changes in neuronal activity as revealed by c-Fos imaging without concomitant cognitive impairments

Over the last decade, animal models have been used to evaluate the physiological and cognitive effects of mobile phone exposures. Here, we used a head-only exposure system in rats to determine whether exposure to 900MHz GSM electromagnetic fields (EMF) induces regional changes in neuronal activation as revealed by c-Fos imaging. In a first study, rats were exposed for 2h to brain average specific absorption rates (BASARs) ranging from 0.5 to 6W/kg. Changes in neuronal activation were found to be dose-dependent with significant increases in c-Fos expression occurring at BASAR of 1W/kg in prelimbic, infralimbic, frontal and cingulate cortices. In a second study, animals were submitted to either a spatial working memory (WM) task in a radial maze or a spatial reference memory (RM) task in an open field arena. Exposures (45min) were conducted before each training session (BASARs of 1 and 3.5W/kg). Control groups included sham-exposed and control cage animals. In both tasks, behavioral performance evolved similarly in the four groups over testing days. However, c-Fos staining was significantly reduced in cortical areas (prelimbic, infralimbic, frontal, cingulate and visual cortices) and in hippocampus of animals engaged in the WM task (BASARs of 1 and 3.5W/kg). In the RM task, EMF exposure-induced decreases were limited to temporal and visual cortices (BASAR of 1W/kg). These results demonstrate that both acute and subchronic exposures to 900MHz EMFs can produce biological effects, but these effects were not sufficient to induce detectable cognitive deficits in the tasks used here.