## 4 The Effect of RF Exposure _in Vivo_: New Insights on Biosystem Functions
### Physiopathology of the Brain
Variation of barrier permeability may occur as a consequence of pathologies or traumas, such as after stroke. However, an increase of permeability is seldom required for drug delivery and substance exchanges. BBB permeability can be transiently increased by pulsing low frequency electromagnetic field [73]. _In vivo_, GMS 900 MHz whole-body exposure of rats for 2 h per day for 7 consecutive days (SAR up to 14 mW/kg) increases BBB permeability that lasts up to 14 days after treatment. More importantly in these settings, no neuronal loss was described [74]. Although transient opening of the BBB could be exploited for therapeutic purpose, the benefit/risk balance is to be cautiously evaluated. Concern has been raised about the potential negative influence of RF on a developing brain [75]. Brain development in mammals is time and growth factor-dependent and extremely sensitive to external insult that might compromise future network functions. It has been shown that pre- and post-natal exposure of rat embryos to commercial mobile phone RF induced an increase of neurodegeneration in Purkinje cells in the cerebellum of rats assessed during adulthood [76]. Moreover, supplementation of a lycopene (natural antioxidant)-rich diet partially prevents neurodegeneration coincidental with caspase 3-dependent apoptotic cascade. Although no specific indication of the exposure time was given, other than \"pre and post natal period\", these results are quite impressive and at the same time alarming if scaled up to the human conditions. Equally noteworthy is the effect of RF 900 MHz long-term application on juvenile rats [77] that appeared to be more susceptible to oxidative stress metabolism measured in peripheral investigated tissues and blood. This effect is likely due to the altered level of blood glutathione (GTH). Similarly, _in vitro_ culture of bone marrow cells from mature rats showed that cytogenotoxic damage was more remarkable than in adults [78]. Melatonin is another important molecular player regulating brain physiology. Several groups investigated the disruptive effect of EMF on the production of the hormone melatonin by the CNS pineal gland, which controls the body's circadian rhythms [79]. Melatonin production is sensitive to light and to exposure of a different range of EMF (recently reviewed in [80]). This evidence indicated melatonin as a possible target for sleep-related disorders. However, there is a lack of solid evidence to suggest a significant impact of EMF exposure on sleep quality in animal models or in the population [81]. Melatonin suppression by EMF has been indicated as a potential risk factor for breast cancer, though no direct tumorigenic effect was observed. This hormone activates specific receptors, namely MT1 [82]. However, it also acts as a natural free radical antioxidant scavenger. This would explain its beneficial effect in reducing EMF-induced damage in breast cancer model [83] and its neuroprotective rescue after RF oxidative stress induction in neuron primary culture [84]. Interestingly, melatonin has been reported to play a relevant role in regulation of human newborn protection in enhanced environmental oxidative stress (OS) present at time of birth. Preterm babies are highly prone to OS and to the toxic effect of free radicals, as for example those involved in perinatal brain lesion, as babies' defense homeostatic neuroprotective mechanisms are not fully developed. Therefore, the impact of EMF exposure of newborn babies to EMF derived from nursing incubators cannot be overlooked [85]. A slight transitory increase in urine metabolite indicates an overproduction of melatonin in babies removed from the incubators with respect to control babies; however, the real implication of this finding is not yet fully understood.