New View on the Impact of the Low-Frequency Electromagnetic Field (50 Hz) on Stress Responses: Hormesis Effect

Abstract

Introduction: Low-frequency electromagnetic field (50 Hz) (EMF) can modify crucial neuronal processes. Existing data indicate that exposure to EMF may represent a mild stressor and contribute to disturbances of hypothalamic-pituitary-adrenal (HPA) axis. The important regulatory pathways controlling HPA axis activity include two types of corticosteroid receptors: mineralocorticoid (MR) and glucocorticoid (GR) receptors. There are particularly abundant in the hippocampus, a key locus of HPA axis feedback control. The research aimed at determining whether 1) EMF exhibits hormesis, it means bidirectional action depending on EMF intensity (1 or 7 mT), and 2) repeated EMF exposure changes stress response to subsequent stress factors. Methods: The exposure (7-day, 1h/day) of adult rats to EMF (1 mT and 7 mT) was repeated 3 times. HPA axis hormones and their receptors were analysed after each following exposure. Moreover, the impact of EMF exposure on hormonal and behavioural responses to subsequent stress factor - open-field test was evaluated. Results/Discussion: Our data suggest that exposure to EMF can establish a new “set-point” for HPA axis activity. The direction and dynamics of this process depend on the intensity of EMF and the number of exposures. EMF of 1 mT induced an adaptive stress response, but 7 mT EMF caused sensitization. Consequently, EMF changed the vulnerability of the organism to a subsequent stress factor. We have also shown the increase of MR mRNA abundance in hippocampus of 1 mT EMF exposed rats, which can represent the possible neuroprotective response and suggest therapeutic properties of electromagnetic fields.

Transcriptomic Analysis of Gene Expression and Effect of Electromagnetic Field in Brain Tissue after Traumatic Brain Injury

“…A later onset of electrical stimulation is associated with better clinical outcomes. However, electrical stimulation for 7 days after 7 weeks of TBI was found to have no persistent effect [ 46 ]. Thus, it is important to investigate the time, frequency, and doses of EMF application for a favorable outcome.…”