Suppression of experimental allergic encephalomyelitis is specific to the frequency and intensity of nocturnally applied, intermittent magnetic fields in rats

Female Lewis rats (n = 72) were inoculated with an emulsion of spinal cord and complete Freund's adjuvant. They were then exposed for approximately 6 min every hour between midnight and 08:00 h for 2 weeks to either 7 or 40 H z amplitude-modulated magnetic fields whose temporal pattern was designed t o simulate a (geomagnetic) storm sudden commencement. The peak strengths of the fields averaged between either 30-50 nT (low intensity) or 500 nT thig h intensity). Rats exposed to the 7 Hz, low intensity magnetic fields displ ayed significantly less severe overt signs of experimental allergic encepha lomyelitis than rats exposed to either of the two intensities of the 40 Hz fields, the high intensity 7 Hz field, or the reference (<10 nT) condition. The latter groups did not differ significantly from each other. Predicted severity based upon the numbers of foci of infiltrations of lymphocytes wit hin the brains of the rats also demonstrated the ameliorating effects of th e low intensity, 7 Hz exposures. These results suggest very specific charac teristics of complex, weak magnetic fields within the sleeping environment could affect the symptoms of autoimmunity. (C) 2000 Elsevier Science Irelan d Ltd. All rights reserved.