この研究は、ラットの内側嗅内皮質（MEC）表層での樹状突起棘の密度および形態に対する50Hz磁界ばく露（0.5 mT）の影響を調べた。ばく露は、毎日4時間（午後2－6時）、14日間または28日間連続した。20匹のSD雄ラットを5匹ずつの4群に分けた：14日間ばく露群、28日ばく露群、およびそれぞれの無ばく露対照群である。その結果、14および28日ばく露群のどちらでも、錐体ニューロンの基底樹状突起および星状ニューロンの樹状突起における棘の密度減少が見られた；ばく露後に密度の変化が見られた棘の形状（キノコ型または隆起型）は細胞タイプに特異的であった（星状ニューロンの樹状突起では隆起型の若干の増加、錐体ニューロンの基底樹状突起ではキノコ型の有意な減少など）､などを報告している。
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To examine the effects of exposure to extremely low frequency magnetic fields on the morphology in dendritic spines of dendrites in the brain of rats.
The structure and density of dendritic spines is a crucial determinant of neuronal input-output transformation. Several types of dendritic spines exist which are named in accordance to their morphology (thin, mushroom, stubby, branched).The gain, loss, and morphological remodeling of dendritic spines is associated with learning and memory abilities and could therefore explain impairments in cognitive functions through magnetic fields as partially found in previous studies (e. g. Sienkiewicz et al., Cui et al.).
Rats were divided into four groups (n=5 per group): 1.) exposure for 14 days, 2.) sham exposure for 14 days, 3.) exposure for 28 days and 4.) sham exposure for 28 days. Afterwards, the rats were killed and the brain was removed.
| 周波数 | 50 Hz |
|---|---|
| タイプ |
|
| 波形 |
|
| ばく露時間 | 4 h/day for 14 or 28 days |
| ばく露の発生源／構造 | |
|---|---|
| チャンバの詳細 | the 4 groups of rats were simultaneously exposed in their usual plastic cages |
| ばく露装置の詳細 | round coil electromagnet with a 1000 turned copper wire |
| Sham exposure | A sham exposure was conducted. |
| 測定量 | 値 | 種別 | Method | Mass | 備考 |
|---|---|---|---|---|---|
| 磁束密度 | 0.5 mT | mean | - | - | in the center of the coils |
In the dendrites of stellate neurons and the basal dendrites of exposed rats (14 and 28 days), a significantly reduced dendritic spine density was found in comparison to the control group. These alterations were due to the loss of the thin and branched dendritic spines. For the stellate neurons, the exposure led to a slight but significant increase in the density of stubby dendritic spines after 28 days, while it did not affect the density of mushroom dendritic spines at the same time. In the basal dendrites of pyramidal cells from exposed rats, a significant decrease in the mushroom spine density was observed after 28 days compared to control group, while the stubby spine density was significantly reduced after 14 days, but partially restored after 28 days. In the apical dendrites of pyramidal cells, the exposure induced a significant reduction in the spine density after 28 days compared to the control group.
The authors conclude that the exposure to extremely low frequency magnetic fields changed the density and morphology of dendritic spines of dendrites in the brain of rats and that these alterations could lead to an impairment in cognitive functions.
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