【目的】パルス磁界は神経再生に有効な影響を与えることが知られている。しかし、パルス磁界下での末梢神経再生における神経伝導特性はほとんど研究されていないので、本研究でその特性を調べる。【方法】ラットの損傷した座骨神経にパルス磁界ばく露を実施し、その後神経を取り出してサッカロースギャップ記録法を用いて伝導特性を検査した。【結果】損傷後の末梢神経は反復的な刺激に対する感受性が非常に高まっていた。刺激周波数を上昇させると複合活動電位（CAP）の減少は大きくなったが、その減少は損傷後38日群に比べ損傷後15日群の方が大きかった。損傷後38日間のパルス磁界ばく露群はCAPの伝導において有意な差異を生じた。その上、パルス磁界処置により、神経の異常な電気生理学的活動（活動電位後過分極、脱分極の遅れ）は改善された（4アミノピリジンを用いて測定した）。【結論】パルス磁界下で修復された神経におけるインパルス伝導を調べた結果、神経損傷後に観察された信号伝達やイオンチャネル機能の異常はパルス磁界処置によって回復された可能性が示された。
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To study the conduction characteristics of regenerating peripheral nerves under pulsed magnetic fields.
The sciatic nerve of rats was crushed with a surgical forceps. After the wound was closed, the animals were allowed to recover for 15-38 days (and exposed). After nerve crush injury and damage to the myelin sheath 4-aminopyridine sensitive potassium ion channels are reorganized (following injury the incomplete regeneration of the myelin sheath causes an increase in potassium currents through these ion channels).
The sciatic nerves were resected, placed in a sucrose gap apparatus and stimulated with short (0.05 ms) depolarizing pulses. The nerves were stimulated with a single stimulus every minute for 30 min at the lowest stimulation rate. To examine the stimulation frequency, three consecutive frequencies (10, 40, and 100 Hz) were used.
The following groups were investigated: two sham crush surgery (same surgical conditions, but no crush) groups (each n=6; sham exposed for 15 or 38 days) and four crush injury groups (each n=8; two exposure groups (exposed for 15 or 38 days) and two sham exposure groups (sham exposed for 15 or 38 days). Additionally, there were two groups of intact (unoperated) rats (each n=14; sham exposed for 15 or 38 days) and two groups of intact rats (each n=8, exposed for 15 or 38 days). Furthermore, two crush groups (no exposure) were investigated after 15 or 38 days and used as controls (each n=8).
for further information on the setup see also: Mert T, Gunay I, Gocmen C, Kaya M, Polat S. 2006. Regenerative effects of pulsed magnetic field on injured peripheral nerves. Altern Ther Health Med 12(5):42-49.
| Modulation type | pulsed |
|---|---|
| Rise time | 0.5 ms |
| Fall time | 9.5 ms |
| Additional information |
triangular waveform |
| ばく露の発生源／構造 | |
|---|---|
| ばく露装置の詳細 | pair of Helmholtz coils with a diameter of 60 cm, placed 30 cm apart in a Faraday cage; rats placed in a 30 cm x 20 cm x 15 cm all-plastic restrainer in the center of the coil system; field homogeneous within 5 % |
| Sham exposure | A sham exposure was conducted. |
| Additional information | for pulse trains of (1 Hz, 10 Hz, 40 Hz, 100 Hz) with an interval of 1 min between them; each pulse train lasted 4 min |
The data showed that pulsed magnetic field application for 15 or 38 days to injured animals did not cause any significant changes in the electrophysiological properties of the nerves. However, in the presence of 4-aminopyridine, significant electrophysiological differences were noted in the pulsed magnetic field-treated 38 days post-crush group (e.g. increase of compound action potential amplitude and decrease of amplitude and prolonged duration of delayed depolarisation).
At the stimulation frequency of 100 Hz, the pulsed magnetic field reduced the influence of 4-aminopyridine on the compound action potential amplitude (but only the highest stimulation frequency of 100 Hz, not at 40 or 10 Hz).
Taken together, these data suggest that application of pulsed magnetic field for 38 days may provoke the process of myelin compaction, or may decrease the breaks in the myelin sheath and prevent the appearance of abnormal impulse patterns.
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