Possible effects of radiofrequency electromagnetic radiation on contextual fear conditioning, hippocampal perivascular space, apoptosis and adrenal gland microarchitecture in rats.

Numerous studies have indicated the potential for non-thermal biological effects of mobile telecommunications technology, especially on the central nervous system. The hippocampus, located in the temporal lobe, is of particular interest because it is integral to episodic memory formation and behavioral inhibition. This publication characterizes the impact of 900 MHz mobile phone radiation on behavioral responses, the hypothalamic–pituitary–adrenal (HPA) axis, and structural changes in the hippocampus and adrenal cortex of rats.

Thirty-six young male Wistar rats were equally divided into three groups: unexposed control, sham-exposed control, and RF-exposed (n = 12). A commercial GSM mobile phone was placed centrally within each cage, silenced, and auto-dialed 50 times per hour for one hour daily over four consecutive weeks. The radiation parameters were a frequency of 900 MHz, a manufacturer-reported specific absorption rate (SAR) of 1.15 W/kg, and a measured maximum power density of 1.466 W/m². Behavioral assessments employed a passive-avoidance paradigm to evaluate contextual fear conditioning and memory consolidation. Histological evaluations included the quantification of hippocampal perivascular spaces and apoptotic cell counts (n = 3) in the CA3 region, as well as the qualitative histopathology of the adrenal cortex.

RF-exposed rats exhibited pronounced hyperactivity and anxiety-like behaviors compared to both control groups. This was accompanied by significantly impaired memory performance. Enlargement of hippocampal perivascular spaces was statistically significant only versus the unexposed control group. Apoptotic cell counts in the CA3 region showed an upward trend, though they did not reach statistical significance. Qualitative observations in the adrenal zona fasciculata revealed apoptotic alterations, lymphocytic infiltrates, and sinusoidal congestion. Other cortical regions and the medulla remained histologically unaltered.

Chronic, non-thermal exposure to 900 MHz mobile phone radiation induced significant alterations in anxiety-related memory and structural remodeling of the hippocampus and adrenal cortex. The authors propose that HPA-axis dysregulation is an underlying mechanism. However, this hypothesis requires further substantiation through the measurement of stress hormones (e.g. corticosterone). Further investigations are warranted to delineate the molecular pathways involved and to quantify endocrine parameters.

Editor's note:

The study’s strengths lie in its use of a real-world RF source, conservative exposure duration, inclusion of sham and unexposed controls, and a multidisciplinary approach integrating behavior and histology. However, the small sample size for apoptotic analysis (n = 3) was not clearly communicated and may obscure statistically significant effects. Overall, the findings corroborate earlier reports of hippocampal damage under non-thermal RF exposure (Zheng et al., 2023; Karimi et al., 2018; Tan et al., 2022). These reports document HPA axis dysregulation, anxiety disorders, impairments of synaptic plasticity or memory, and changes in molecular signaling pathways in mammals. (RH)

Karimi N, Bayat M, Haghani M, Saadi HF, Ghazipour GR. (2018). 2.45 GHz microwave radiation impairs learning, memory, and hippocampal synaptic plasticity in the rat. Toxicology and Industrial Health, 34(12), 873–883. https://doi.org/10.1177/0748233718798976

Tan B, Canturk Tan F, Yalcin B, Dasdag S, Yegin K, Yay AH. (2022). Changes in the histopathology and in the proteins related to the MAPK pathway in the brains of rats exposed to pre and postnatal radiofrequency radiation over four generations. Journal of Chemical Neuroanatomy, 126, 102187. https://doi.org/https://doi.org/10.1016/j.jchemneu.2022.102187

Zheng R, Zhang X, Gao Y, Gao D, Gong W, Zhang C, Dong G, Li Z. (2023). Biological effects of exposure to 2650 MHz electromagnetic radiation on the behavior, learning, and memory of mice. Brain and Behavior, 13(6), 1–13. https://doi.org/10.1002/brb3.3004

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