60 Hz Magnetic fields and Central Cholinergic Activity: Effects of Exposure Intensity and Duration.

Lai H, Carino MA

Bioelectromagnetics (In press) 1998

In previous research, we have found that acute exposure to a 60 Hz magnetic field caused a decrease in cholinergic activity in the frontal cortex and hippocampus of the rat. In the present study, the effects of exposure to different intensities of the magnetic field and durations of exposure were investigated.

In an experiment, rats were exposed to a 60 Hz magnetic field for 60 min at a flux density of either 0.5, 1.0, 1.5, or 2.0 mT.

A significant decrease in cholinergic activity was observed in the frontal cortex and hippocampus immediately after exposure to the 2.0 mT field. No significant effect was observed at lower intensities. In another experiment, effect of exposure to a 1.0 mT magnetic field for 30, 45, 60, and 90 min was investigated. A decrease in cholinergic activity was found in both brain areas after 90 min of exposure.

No significant effect was observed after shorter durations of exposure. In a further experiment, the exposure duration was extended to 3 hrs at flux densities of 0.5, 0.1, and 0.05 mT. A significant decrease in cholinergic activity was observed in the frontal cortex and hippocampus of the rat immediately after exposure to all the intensities. It is concluded that the intensity and duration of exposure interact. By increasing the duration of exposure, effects can be observed at lower intensities.