Table 1.

Effects of magnetic field exposure on locomotor activity

FieldDurationNumber of rats% CirclingMean circles% RearingMean rears
Experiments 1a and 2
 0 T30 min2251913.8  ± 0.5
 7 T30 min17472.4  ± 0.6*592.8  ± 0.9*
 14 T30 min17712.6  ± 0.4*00*
Experiment 1b
 14 T0 min600  ± 01004.8  ± 0.8
 14 T1 min600  ± 01001.8  ± 0.7*
 14 T5 min8505.0  ± 2.5672.3  ± 0.5*
 14 T10 min14572.9  ± 0.7432.2  ± 0.5*
 14 T20 min8632.8  ± 0.5131*
 14 T30 min17712.6  ± 0.400*
Experiment 3
 0 T Down30 min1200834.9  ± 1.1
 14 T Down30 min15736.1  ± 2.7332.0  ± 0.3*
 14 T Up30 min13778.4  ± 2.5541.6  ± 0.3*
  • Locomotor activity of rats after magnetic field exposure was scored for tight circling and rearing by a blind observer from videotape records. Rats were sham exposed (0 T) or exposed to 7 or 14 T magnetic fields for 0–30 min. Shown are the number of rats tested, the percentage of rats displaying circling or rearing, and the mean ± SEM number of circles or rears counted for those rats that showed any circling or rearing (i.e. non-zero means). In experiments 1a and 2, rats were exposed head-up to a 7 or 14 T magnetic field for 30 min; both exposures induced circling and suppressed rearing. In experiment 1b, rats were exposed head-up to 14 T for 0–30 min; significant circling was induced by ≥5 min of exposure, and rearing was significantly suppressed after ≥10 min of exposure. In experiment 3, rats were restrained in either the head-up or head-down orientation within a 14 T magnetic field for 30 min. Circling was induced and rearing was suppressed in both groups, but the direction of circling depended on the rats' orientation within the field (Fig. 1).