研究のタイプ: 医学/生物学の研究 (experimental study)

[妊娠の全期間を通して弱強度の複合磁界ばく露を受けたラットにおける海馬の神経発達異常] med./bio.

Neurodevelopmental anomalies of the hippocampus in rats exposed to weak intensity complex magnetic fields throughout gestation.

掲載誌: Int J Dev Neurosci 2012; 30 (6): 427-433

この研究は、ラットを用いた実験で、出生前の低レベル磁界ばく露による出生後のラットの脳の発達への影響を調べた。妊娠中のWistarラットに、妊娠期間中(21日間)、24時間連続で磁界ばく露を与えた。ばく露レベルは、4レベルのうちのいずれか一つのレベル(参照:5 - 20 nT、低:30 - 50 nT、中:90 - 580 nT、高:590 - 1200 nT )とし、磁界は様々なシーケンスの4つのパターン(複合パターン、LTPパターン、パルス化50 Hzパターンなど)を用いた。すべてのパターンは10秒間繰り返され、その後40秒間は磁界なしの構成で反復された。一つのパターンで24時間ばく露を行い、4日間で4つのパターンが繰り返された。その結果、低ばく露群から出生した仔ラットは、文脈的恐怖学習の障害を示した;また、海馬細胞学的および形態学的発達の異常として、特に、海馬全体のサイズ縮小、CA1およびCA3領域の微かな発育不全が見られた;対照的に、これより弱いまたはより強いばく露レベルでは、海馬の発達または恐怖行動への影響は見られなかった;著者は、これらの知見は磁界レベルの狭い窓効果の可能性を示唆する、と報告している。

The detailed summary of this article is not available in your language or incomplete. Would you like to see a complete translation of the summary? Then please contact us →

研究目的(著者による)

To investigate the effect of weak intensity magnetic fields on the prenatal brain development.

詳細情報

Pregnant rats were continuously exposed to one of four intensities during the pregnancy: 1.) 5-20 nT, 2.) 30-50 nT, 3.) 90-580 nT und 4.) 90-1200 nT (n=2 per group). After one year, the male offspring (n=6-7 per group) were used in the open field test and the contextual fear conditioning was examined. Additionally, the number and the structure of hippocampal neurons were analyzed (n=4 per group).
Previous studies showed that there were no differences between rats exposed to a weak magnetic field of 5-20 nT and a control group without any magnetic field. Therefore, in this study, the reference group (5-20 nT) was used as a control.
The experiment was performed twice.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 50 Hz
Modulation type: pulsed
ばく露時間: continuous to different field patterns for 24 h/day during gestation (21 days)
  • 磁束密度: 20 nT maximum (B = 5 - 20 nT reference group)
  • 磁束密度: 50 nT maximum (B = 30 - 50 nT low-intensity group)
  • 磁束密度: 580 nT maximum (B = 90 - 580 nT medium-intensity group)
  • 磁束密度: 1,200 nT maximum (B = 590 - 1200 nT high-intensity group)

ばく露1

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
ばく露時間 continuous to different field patterns for 24 h/day during gestation (21 days)
Additional information temporal structures of a complex magnetic field (composite, LTP-like, and non-sinusoidal 50 Hz field)
Modulation
Modulation type pulsed
Additional information

composite pattern: composed of 40 sequential 250 ms signatures of specific frequency-modulated patterns as well as of those derived from mathematical relationships; LTP-pattern: repeated sequences of a primer pulse followed 170 ms later by four working pulses; 50 Hz pattern: rise time and fall time of 1 ms and a plateau and trough of 20 ms; all patterns were presented in a repeating cycle for 10 s, followed by 40 s of no field for 24 h before the next pattern was initiated; each pattern repeated every fourth day throughout gestation

ばく露装置
ばく露の発生源/構造
ばく露装置の詳細 rats kept in one of four identical compartments of a 140 cm x 33 cm x 33 cm plastic cage; identical Herlmholtz coils positioned at each end of the cage; coils created by wrapping 38 cm x 33 cm x 27 cm cartons with 305 m of 30 AWG wire
パラメータ
測定量 種別 Method Mass 備考
磁束密度 20 nT maximum 測定値 - B = 5 - 20 nT reference group
磁束密度 50 nT maximum 測定値 - B = 30 - 50 nT low-intensity group
磁束密度 580 nT maximum 測定値 - B = 90 - 580 nT medium-intensity group
磁束密度 1,200 nT maximum 測定値 - B = 590 - 1200 nT high-intensity group

Reference articles

  • Whissell PD et al. (2009): [LTPパターン化磁界への出生前ばく露:特異辺縁構造に与える定量的作用と背景的に条件付けられる懸念]
  • St-Pierre LS et al. (2008): [弱い磁界(50-500nT)に出生前にばく露された成獣ラットにおける血液化学と海馬の組織形態学変化]
  • St-Pierre LS et al. (2003): [ナノテスラ範囲内の複雑なシーケンスの磁界に出生前ばく露されたラットの海馬形成における顕著な組織形態異常]

ばく露を受けた生物:

方法 影響評価項目/測定パラメータ/方法

研究対象とした生物試料:
研究対象とした臓器系:
調査の時期:
  • ばく露後

研究の主なアウトカム(著者による)

Individual analyses of open field related behaviors revealed no significant differences between any of the exposure conditions. In the fear conditioning, it was found that exposure to the low-intensity (30-50 nT) complex magnetic field during prenatal development resulted in a significant reduction of freezing time compared to the reference group (5-20 nT). Additionally, rats exposed to the low-intensity (30-50 nT) complex magnetic field showed anomalies in the cytological and morphological development of the hippocampus (reduction in overall hippocampal size and promoted subtle malformation of some regions) as compared to the reference group (5-20 nT). In contrast, exposure to weaker or stronger intensities of the same complex magnetic field did not interfere with hippocampal development or anxiety behavior.
These findings suggest that prenatal exposure to complex magnetic fields of a narrow intensity window during development could result in subtle but permanent alterations in hippocampal structure and function.

研究の種別:

研究助成

関連論文