この研究は、脊髄損傷（SCI）による持続性疼痛と脳内神経伝達物質濃度に対する超低周波磁界ばく露（MF;17.96 μT, 50 Hz）の影響を調べた。成獣雄Wisterラットの擬似ばく露群（8匹：擬似的外科手術、損傷なし）、SCI群（6匹：外科手術により脊髄損傷）、SCI＋MF群（6匹：MFばく露はSCI手術後から、2時間／日、7日／週、8週間）を用いた。8週間にわたって、週1回の行動テスト（BBBスコア）、第8週の最後に発痛物質フォルマリンの後肢注入による痛み試験（痛み行動を4段階評価：T0～T3）を実施した後、脳組織標本検査を実施した。その結果、フォルマリン痛み試験において、擬似ばく露群に比べSCI群では、フォルマリン注入後60分間の痛みスコア平均値、5分ブロックごとの痛みスコア平均値、すくみ行動の回数は有意に低く、痛みスコアの低いカテゴリー（T0、T1）にいる時間は多かった；このような痛み試験の結果は、SCI群とSCI+MF群では同等であった；SCI群では、大脳皮質、前脳、脳幹の5-HTが低く、脳幹のGABAとNEは高かったが、擬似ばく露群とSCI＋MF群では同等であった；DA、グルタミン酸、グリシンの濃度は各群同じであった、と報告している。
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To examine the effect of magnetic field exposure on the tonic pain behavior and related neurotransmitters in the brain of rats with spinal cord injury.
Rats were divided into three groups for behavioral and neurochemical experiments: 1.) sham operated group (n=8), 2.) spinal cord injury group (n=6) and 3.) spinal cord injury + magnetic field exposure group (n=6). The same number and groups of rats were used for the histological experiment.
After the spinal cord injury, rats were exposed or kept without exposure for 8 weeks. Locomotor activity was assessed weekly while nociception was only recorded at the end of the 8 weeks before rats were sacrified wfor histological and neurotransmitter concentration examination.
ばく露時間: 2 h/day for 7 days/week for 8 weeks
|ばく露時間||2 h/day for 7 days/week for 8 weeks|
|チャンバの詳細||rats were exposed in a non-metal box|
|ばく露装置の詳細||box was placed at the center of four coils connected in series to 50 Hz power supply; coils were wound on circular formers at a diameter of 1000 mm; two outer coils were wound with 18 turns each and two inner coils were wound with 8 turns, respectively; coils produced a uniform magnetic field|
|磁束密度||17.96 µT||effective value||測定値||-||-|
Rats with spinal cord injury showed a significantly reduced locomotor activity compared to the sham group. However, locomotor activity was significantly higher in the "spinal cord injury with magnetic field exposure group" than in the group with spinal cord injury alone.
Pain after formalin injection was significantly decreased in rats with spinal cord injury compared to the sham group, while magnetic field exposure in spinal cord injured rats significantly increased the level of pain compared to rats with spinal cord injury alone.
In spinal cord injured rats, the concentration of serotonin was significantly lower in the cortex and in the rest of the brain in comparison to the sham group, while the concentrations of gamma aminobutyric acid and norepinephrine in the brain stem were significantly increased. A magnetic field exposure diminished these effetcs.
Morphological analysis revealed clear lesions in the spinal cord of spinal cord injured rats with and without magnetic field exposure. However, lesion volume was significantly less in the spinal cord injury group with magnetic field exposure.
The authors conclude that the neurotransmitter changes contribute toward the decreased pain in spinal cord injured rats which is restored by long-term exposure to extremely low frequency magnetic fields.