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. 2011 Sep;20(3):130-6.
doi: 10.5607/en.2011.20.3.130. Epub 2011 Sep 20.

Exposure to extremely low frequency magnetic fields induces fos-related antigen-immunoreactivity via activation of dopaminergic d1 receptor

Eun-Joo Shin  1 , Xuan-Khanh Thi Nguyen, Thuy-Ty Lan Nguyen, Diem-Thu Pham, Hyoung-Chun Kim
Affiliations

Exposure to extremely low frequency magnetic fields induces fos-related antigen-immunoreactivity via activation of dopaminergic d1 receptor

Eun-Joo Shin et al. Exp Neurobiol. 2011 Sep.

Abstract

We previously demonstrated that repeated exposure to extremely low frequency magnetic fields (ELF-MF) increases locomotor activity via stimulation of dopaminergic D1 receptor (J. Pharmacol. Sci., 2007;105:367-371). Since it has been demonstrated that activator protein-1 (AP-1) transcription factors, especially 35-kDa fos-related antigen (FRA), play a key role in the neuronal and behavioral adaptation in response to various stimuli, we examined whether repeated ELF-MF exposure induces FRA-immunoreactivity (FRA-IR) in the striatum and nucleus accumbens (striatal complex) of the mice. Repeated exposure to ELF-MF (0.3 or 2.4 mT, 1 h/day, for consecutive fourteen days) significantly induced hyperlocomotor activity and FRA-IR in the striatal complex in a field intensity-dependent manner. ELF-MF-induced FRA-IR lasted for at least 1 year, while locomotor activity returned near control level 3 months after the final exposure to ELF-MF. Pretreatment with SCH23390, a dopaminergic D1 receptor antagonist, but not with sulpiride, a dopaminergic D2 receptor antagonist, significantly attenuated hyperlocomotor activity and FRA-IR induced by ELF-MF. Our results suggest that repeated exposure to ELF-MF leads to prolonged locomotor stimulation and long-term expression of FRA in the striatal complex of the mice via stimulation of dopaminergic D1 receptor.

Keywords: Fos-related antigen; dopaminergic D1 receptor; extremely low frequency magnetic fields; locomotor activity; striatal complex.

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Figures

Fig. 1
Fig. 1
Experimental schedule for evaluating effects of repeated exposure to extremely low frequency magnetic fields (ELF-MF) on the locomotor activity and fos-related antigen-immunoreactivity (FRA-IR) in the striatum and nucleus accumbens (striatal complex) of the mice. Animals were exposed to ELF-MF (0.3 or 2.4 mT, 1 hour/day) for consecutive 14 days. Thirty minutes before each exposure to ELF-MF, mice were treated with SCH23390 hydrochloride (a dopaminergic D1 antagonist; 0.03 or 0.1 mg/kg, i.p.) or sulpiride (a dopaminergic D2 antagonist; 10 or 20 mg/kg, i.p.). Locomotor activity was measured 0 hour, 1 day, 1 week, 3 months and 1 year after the final ELF-MF exposure using an automated video-tracking system. Mice were sacrificed for immunocytochemical evaluation 90 min after the measurement of locomotor activity. *SCH23390 (a dopaminergic D1 antagonist; 0.03 or 0.1 mg/kg, i.p.) or Sulpiride (a dopaminergic D2 antagonist; 10 or 20 mg/kg, i.p.) was injected 30 min prior to ELF-MF exposure. §Behavioral evaluation followed by immunocytochemical study.
Fig. 2
Fig. 2
Changes in locomotor activity after repeated exposure to extremely low frequency magnetic fields (ELF-MF) in the mice. Locomotor activity was measured 0 hour, 1 day, 1 week, 3 months and 1 year after the final ELF-MF exposure. SCH 0.03 or 0.1=SCH 23390 at 0.03 or 0.1 mg/kg, i.p. Sulp 10 or 20=sulpiride at 10 or 20 mg/kg, i.p. Each value is the mean±S.E.M. of 6 mice. *p<0.05, **p<0.01 vs. Saline+Control, &p<0.05 vs. Saline+0.3 mT ELF-MF, #p<0.05, ##p<0.01 vs. Saline+2.4 mT ELF-MF (One-way ANOVA followed by Fischer's PLSD test).
Fig. 3
Fig. 3
Changes in fos-related antigen-immunoreactivity (FRA-IR) after repeated exposure to extremely low frequency magnetic fields (ELF-MF) in the striatum of the mice. SCH 0.1=SCH 23390 at 0.1 mg/kg, i.p. Sulp 20=sulpiride at 20 mg/kg, i.p. Each value is the mean±S.E.M. of 6 mice. *p<0.01 vs. Saline+Control, &p<0.05, &&p<0.01 vs. Saline+0.3 mT ELF-MF, #p<0.05, ##p<0.01 vs. Saline+2.4 mT ELF-MF (One-way ANOVA followed by Fischer's PLSD test).
Fig. 4
Fig. 4
Changes in fos-related antigen-immunoreactivity (FRA-IR) after repeated exposure to extremely low frequency magnetic fields (ELF-MF) in the nucleus accumbens of the mice. SCH 0.1=SCH 23390 at 0.1 mg/kg, i.p. Sulp 20=sulpiride at 20 mg/kg, i.p. Each value is the mean±S.E.M. of 6 mice. *p<0.01 vs. Saline+Control, &p<0.05, &&p<0.01 vs. Saline+0.3 mT ELF-MF, #p<0.01 vs. Saline+2.4 mT ELF-MF (One-way ANOVA followed by Fischer's PLSD test).
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