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Neurosci Lett. 1994 Jan 17;166(1):59-62.

Circularly polarized 50-Hz magnetic field exposure reduces pineal gland and blood melatonin concentrations of Long-Evans rats.

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  • 1Department of Physiology, Hokkaido University School of Medicine, Sapporo, Japan.


In order to determine if pigmented rats also exhibit melatonin suppression like that described for albino rats exposed to circularly polarized, 50-Hz, 1-muT magnetic fields for 6 weeks, two experiments were conducted with Long-Evans rats. The field-exposed experimental group received circularly polarized, 50-Hz, 1-muT magnetic fields for 6 weeks, the concurrent sham-exposed control group was exposed to the stray field of 0.02 muT. In addition, prior to the exposure experiment, two cage-control groups were placed in the facility for 6 weeks without activation of the 50-Hz magnetic field generation apparatus. Rats were sacrificed at 12.00 and at 24.00 h for collection of plasma and pineal gland: melatonin was determined by radioimmunoassay. Significant reductions of plasma and pineal gland melatonin contents were observed at 0.02 muT as compared to the control values, and a further reduction was observed at 1 muT. As do albino rats, pigmented rats rats also exhibit melatonin suppression when exposed to time-varying magnetic fields.

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