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

Neuroendocrinology. 2023;113(4):423-441. doi: 10.1159/000527878. Epub 2022 Nov 2.

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 the hypothalamic-pituitary-adrenal (HPA) axis. The important regulatory pathways controlling HPA axis activity include two types of corticosteroid receptors: mineralocorticoid receptors (MRs) and glucocorticoid receptors. They 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 days, 1 h/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: 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 in MR mRNA abundance in the hippocampus of 1 mT EMF-exposed rats, which can represent the possible neuroprotective response and suggest therapeutic properties of EMFs.

Keywords: Hypothalamic-pituitary-adrenal axis; Low-frequency electromagnetic field; Mineralocorticoid receptor; Open-field test; Stress response.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Electromagnetic Fields* / adverse effects
  • Hippocampus
  • Hormesis
  • Hypothalamo-Hypophyseal System* / physiology
  • Pituitary-Adrenal System
  • Rats

Grants and funding

This study was supported by National Science Centre, Poland (Grant No. 2017/25/B/NZ7/00638) and project No. POWR.03.05.00-00-Z302/17 “Universitas Copernicana Thoruniensis In Futuro,” co-financed by the European Social Fund − the Operational Programme Knowledge Education Development. Module 5. Interdisciplinary PhD School “Academia Copernicana.”