Table 1.

Effects of magnetic field exposure on locomotor activity

Field	Duration	Number of rats	% Circling	Mean circles	% Rearing	Mean rears
Experiments 1a and 2
0 T	30 min	22	5	1	91	3.8 ± 0.5
7 T	30 min	17	47	2.4 ± 0.6^*	59	2.8 ± 0.9^*
14 T	30 min	17	71	2.6 ± 0.4^*	0	0^*^†
Experiment 1b
14 T	0 min	6	0	0 ± 0	100	4.8 ± 0.8
14 T	1 min	6	0	0 ± 0	100	1.8 ± 0.7^*
14 T	5 min	8	50	5.0 ± 2.5	67	2.3 ± 0.5^*
14 T	10 min	14	57	2.9 ± 0.7	43	2.2 ± 0.5^*
14 T	20 min	8	63	2.8 ± 0.5	13	1^*
14 T	30 min	17	71	2.6 ± 0.4	0	0^*
Experiment 3
0 T Down	30 min	12	0	0	83	4.9 ± 1.1
14 T Down	30 min	15	73	6.1 ± 2.7	33	2.0 ± 0.3^*
14 T Up	30 min	13	77	8.4 ± 2.5	54	1.6 ± 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).