Medical/biological Study (experimental study)

Stress-related endocrinological and psychopathological effects of short- and long-term 50Hz electromagnetic field exposure in rats. med./biol.

PubMed Entry

Journal web site

Aim of study (according to author)
To study the short-term and long-term effects of 50 Hz electromagnetic field exposure on anxiety- and depression-related behavior of rats in connection with the development of chronic stress state.
Background/further details:
Adult male rats (n=32, 8 rats/group (two exposure groups, two sham exposure groups)) were exposed to extremely low frequency electromagnetic fields (50 Hz, 0.5 mT) for 5 days, 8 h daily (short-term exposure) or for 4-6 weeks, 24 h daily (long-term exposure).
The authors hypothesized that long-term extremely low frequency electromagnetic field exposure would result in a chronic stress state accompanied by the permanent activation of hypothalamic-pituitary-adrenal (HPA) axis with consequent anxious and depressive-like behavior (activation of the HPA axis leads to an enhanced secretion of CRF from the hypothalamus provoking the splicing of adrenocorticotropic hormone (ACTH) from proopiomelanocortin (POMC) precursor in the anterior lobe of the pituitary gland. ACTH triggers the secretion of glucocorticoids from the adrenal cortex).
The forced swim test is an animal model often used in the study of depression. It is a 2-day helplessness procedure in which rats swim under conditions in which escape is not possible.

Endpoint

• cognitive/behavioral endpoints: anxiety- and depression-related behaviour, chronic stress

Exposure
General category: electric field, magnetic field, low frequency field, 50/60 Hz (AC)

Field characteristics	Parameters
field 1: 50 Hz exposure duration: continuous for 8 hr/day on 5 days	electric field strength: 525 V/m min value electric field strength: 575 V/m max value magnetic flux density: 0.5 mT (+/- 0.025 mT)
field 2: 50 Hz exposure duration: continuous for 24 hr/day during 6 weeks	electric field strength: 525 V/m min value electric field strength: 575 V/m max value magnetic flux density: 0.5 mT (+/- 0.025 mT)

Exposed system:
animal (species/strain): rat/Sprague-Dawley
whole body exposure

Methods
Endpoint/Measurement parameters/Methodology

• molecular biosynthesis: proopiomelanocortin (POMC) mRNA expression in the pituitary gland (in situ hybridization)
• endocrine changes: chronic stress-related endocrine changes (adrenal gland and thymus weight; blood hormone levels of ACTH and corticosterone (radioimmunoassay); hematocrit level; blood glucose level)
• cognitive/behavioral endpoints: anxiety-related behaviour (elevated plus maze test; e.g. time/number of entries in the open/closed arm, time spent in the central part, number of rearings) and depression-related behaviour (forced swim test; long-term exposure group only; duration of floating, swimming and struggling)
• others: body weight

Main outcome of study (according to author)
Both exposure conditions were ineffective on somatic parameters, i.e. none of the changes characteristic to chronic stress (body weight reduction, thymus involution and adrenal gland hypertrophy) were present.
The data showed that the SHORT-TERM, repeated extremely low frequency electromagnetic field did not induce any sign of chronic stress or any symptom of anxiety-like behavior with the examined parameters in rats.
After continuous LONG-TERM exposure, elevated blood glucose levels, elevated POMC mRNA level in the anterior lobe of the pituitary gland, and enhanced susceptibility for depression-like behavior were detected.
In conclusion, long and continuous exposure to relatively high intensity electromagnetic field (the average intensity of the human exposure is normally much smaller than in the present experiment) may count as a mild stress situation and could be a factor in the development of depressive state or metabolic disturbances.

(Study character: medical/biological study, experimental study, full/main study)

Study funded by

• Hungarian Scientific Research Fund (OTKA), Hungary

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