Seven groups of mice were examined (n=30 per group): 1.) no exposure + saline injection (control group), 2.) exposure at 0.3 mT + saline injection, 3.) exposure at 2.4 mT + saline injection, 4.) exposure at 2.4 mT + injection of 0.03 mg SCH (SCH23390 hydrochloride, a dopaminergic D1 receptor antagonist) per kg body weight, 5.) exposure at 2.4 mT + injection of 0.1 mg SCH per kg body weight, 6.) exposure at 2.4 mT + injection of 10 mg Sulp (sulpiride, a dopaminergic D2 receptor antagonist) per kg body weight and 7.) exposure at 2.4 mT + injection of 20 mg Sulp per kg body weight.
The solutions of saline, SCH and Sulp were injected 30 minutes prior to the daily exposure for 14 days. Locomotor behavior was tested directly, 1 day, 1 week, 3 month and 1 year after the exposure period (6 rats per group and point of time, resepectively). Animals were killed for immunohistochemical analyses 90 minutes after measurement of the locomotor activity.
|Exposure duration||1 h/day for 14 days|
In the exposure groups (group 2 + 3), the locomotor activity was significantly increased in a field intensity-dependent manner directly and 1 day after the exposure period (with 2.4 mT also after 1 week) in comparison to the control group, but returned near the level of the control group after 3 month. An administration of SCH (group 4 + 5), but not Sulp (group 6 + 7) reduced the locomotor activity significantly compared to the exposure group with saline injection (group 3).
In the striatum and the nucleus accumbens of all exposed mice, the Fos-related antigen immunoreactivity was significantly increased in a field intensity-dependent manner compared to the control group. The highest levels were found directly after the exposure period. They decreased continuously over the year but remained significantly higher than those of the control group. An injection of SCH, but not Sulp significantly lowered the immunoreactivity of the Fos-related antigen compared to the 2.4 mT exposure group with saline injection, however the values remained significantly higher when compared to the control group.
The results indicate that exposure to extremely low frequency magnetic fields induces Fos-related antigen immunoreactivity in the brain of mice and increases the locomotor activity via stimulation of a dopaminergic D1 receptor.