Brain structure alterations following neonatal exposure to low-frequency electromagnetic fields: A histological analysis

Abstract

Nitric oxide (NO) and electromagnetic fields (EMF) have been extensively studied for their roles in neurobiology, particularly in regulating cerebral functions and synaptic plasticity. This study investigates the impact of EMFs on NO modulation and its subsequent effects on neurodevelopment, building upon prior research examining EMF exposure's consequences on Wistar albino rats. Rats were exposed perinatally to either tap water, 1 g/L of L-arginine (LA) or 0.5 g/L of N-methylarginine (NMA). Half of the rats in each group were also exposed to a 7-Hz square-wave EMF at three separate intensities (5, 50 and 500 nT) for 2–14 days following birth. Animals were allowed to develop, and their brains were harvested later in adulthood (mean age = 568.17 days, SD = 162.73). Histological analyses were used to elucidate structural changes in key brain regions. All brains were stained with Toluidine Blue O (TBO), enabling the visualization of neurons. Neuronal counts were then conducted in specific regions of interest (e.g. hippocampus, cortices, amygdala and hypothalamus). Histological analyses revealed significant alterations in neuronal density in specific brain regions, particularly in response to EMF exposure and pharmacological interventions. Notable findings include a main EMF exposure effect where increased neuronal counts were observed in the secondary somatosensory cortex under low EMF intensities (p < 0.001) and sex-specific responses in the hippocampus, where a significant increase in neuronal counts was observed in the left CA3 region in female rats exposed to EMF compared to unexposed females (t(18) = 2.371, p = 0.029). Additionally, a significant increase in neuronal counts in the right entorhinal cortex was seen in male rats exposed to EMF compared to unexposed males (t(18) = 2.216, p = 0.040). These findings emphasize the complex interaction among sex, EMF exposure and pharmacological agents on neuronal dynamics across brain regions, highlighting the need for further research to identify underlying mechanisms and potential implications for cognitive function and neurological health in clinical and environmental contexts.