Suppression of experimental allergic encephalomyelitis in rats by 50-nT, 7-Hz amplitude-modulated nocturnal magnetic fields depends on when after inoculation the fields are applied.

Abstract

Female Lewis rats (n = 88) were inoculated with an emulsion of spinal cord and complete Freund's adjuvant. They were then exposed in 11 separate blocks of experiments over a year period for approximately 6 min every hour between midnight and 08:00 h during post-inoculation nights 1-7, 8-16, 1-16, or 9 and 10 to 50-nT, 7-Hz, amplitude-modulated magnetic fields or to sham field (control) conditions. Compared to the control rats those exposed to the magnetic fields for nights 1-7 and nights 9-10 displayed more severe clinical symptoms while those exposed for nights 1-16 or 8-16 showed less severe symptoms. There was a strong correlation between the severity of the clinical symptoms in the control groups and the global geomagnetic activity 9 and 10 days after inoculation. These results suggest that the immunosuppressive effects of weak nocturnal magnetic fields may depend upon when they are applied during various stages in the development of a disease.