この研究は、ウィスター雌ラットに60Hz電磁界（EMF）ばく露を9日間または30日間、反復的に与え（ばく露パラメータは抄録には不記載）、ばく露終了後に社会認知行動テストを実施し、その後、嗅球でのエストロゲン受容体（α-およびβ- ER）発現を免疫組織化学的測定した。実験には、無傷、卵巣切除（OVX）、卵巣切除+エストラジオール補充（OVX+E2）の3条件のラットを用いた。その結果、OVX群では、9日間のEMFばく露後に社会認知行動異常が見られたが、OVX+E2群では異常は見られず、30日ばく露でも同様であった；9日間のEMFばく露では、無傷ラット群でβ-ER発現が増加したが、他の群では増加が見られなかった；30日ばく露では、無傷ラット群でβ-ER発現が低下したが、他の群では増加した、と報告している。
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The effects of exposure of rats to a 60 Hz magnetic field on the social recognition behavior and expression of estrogen receptors in the olfactory bulb should be investigated.
The olfactory bulb plays a fundamental role in rat social recognition, e.g., of family members, and it is suggested that estrogen plays also an important role in social behavior. Studies demonstrated that mice lacking estrogen receptors showed modified social behavior. In a previous study (Reyes-Guerrero et al. 2006), the authors demonstrated that social recognition in ovariectomized rats was improved by estrogen supplement and exposure to an extremely low frequency magnetic field.
Female virgin rats were divided into the following groups (n=20 each): 1) exposure of intact rats to the magnetic field, 2) exposure of ovariectomized rats to the magnetic field, 3) exposure of ovariectomized rats supplemented with 17 β-estradiol (25 µg/kg daily, subcutaneous) to the magnetic field, 4) sham exposure of ovariectomized rats supplemented with estradiol, 5) sham exposure of ovariectomized rats, 6) sham exposure of intact rats. Each group was divided into 2 subgroups (n=10 each); one subgroup was exposed for 9 days, the other one for 30 days.
| 周波数 | 60 Hz |
|---|---|
| タイプ |
|
| ばく露時間 | for 2 hours/day for 9 days |
| ばく露の発生源／構造 | |
|---|---|
| ばく露装置の詳細 | exposure system consisted of a chamber with a pair of circular double-wrapped Helmholtz coils, each made of 180 turns of 18-gage copper wire and with an internal diameter of 36 cm; coils were placed symmetrically one on each side of the experimental area (50 x 50 x 18 cm3) along the axis, separated by a distance equal to the radius of the coil and connected in parallel; field was uniform; experiments were performed at 22-23°C room temperature |
| Sham exposure | A sham exposure was conducted. |
| Additional information | sham-exposure followed the same protocol, but with the coils turned off |
| 測定量 | 値 | 種別 | Method | Mass | 備考 |
|---|---|---|---|---|---|
| 磁束密度 | 1 mT | - | 測定値 | - | - |
| 周波数 | 60 Hz |
|---|---|
| タイプ |
|
| ばく露時間 | for 2 hours/day for 30 days |
| ばく露の発生源／構造 |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| 測定量 | 値 | 種別 | Method | Mass | 備考 |
|---|---|---|---|---|---|
| 磁束密度 | 1 mT | - | 測定値 | - | - |
Social recognition was significantly impaired in ovariectomized rats exposed to the magnetic field (group 2) compared to intact sham exposed rats (group 6) after 9 and 30 days of exposure. This effect could be negated by supplement of 17 β-estradiol (group 3). After 30 days of exposure, also intact rats exposed to the magnetic field (group 1) showed significantly impaired social recognition compared to all groups without magnetic field exposure.
The authors state, that the protein expression data indicate that the amount of α- and β-estradiol receptors may be modified by exposure to the magnetic field and that this modification in the receptors correlates with changes in the olfactory behavior. However, no significant effect of the magnetic field alone on the protein expression of estrogen receptors can be seen. (remark EMF-Portal: results and conclusions are not consistent and not comprehensive with respect to the figures.)
The authors conclude that exposure of rats to a 60 Hz magnetic field might alter social recognition behavior. Supplement of estrogens might protect from this effect and could increase the expression of estrogen receptors in the olfactory bulb, which might play a role in olfactory memory.
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