Open‐field behavior in rats exposed prenatally to a low intensity‐low frequency, rotating magnetic field

Two experiments were conducted to study the behavioral effects of prenatal exposure to a low intensity, ultra‐low‐frequency magnetic field. In Experiment I, 117 albino rats that had been exposed continuously during their prenatal development to a 3 to 30 gauss, 0.5 Hz rotating magnetic field (RMF), and 83 control rats that had been exposed renatally to control conditions, were tested in an open field at 21 to 25 days of age. RMF‐exposed animals traversed significantly fewer squares than their controls in the open field (p < .001), but defecated significantly more in that situation (p < .001). RMF‐exposed males also traversed significantly fewer squares than the RMF‐exposed females (p < .05). Three RMF‐exposed litters that were nursed by control mothers did not differ significantly in open‐field activity from the pups in the 4 RMF‐exposed litters from which they were taken at birth. In Experiment 2, in which the experimenters did not know whether the subject was a RMF‐exposed rat or a control rat, 19 RMF‐exposed rats again traversed significantly fewer squares than the 20 control rats (p < .01).