臺灣博碩士論文加值系統

靜磁場是否會對神經細胞的運作造成影響﹖這是我們要探討的問題。以螯蝦逃跑迴路中的神經細胞作為研究的對象，結果發現靜磁場會強化神經細胞用來接收與傳遞訊息的類比電子信號 : excitatory postsynaptic potentials (EPSPs)以及action potentials (APs)。靜磁場對於兩者的影響很相似，需要累積一定的暴露時間，增強的效果才會顯現出來。神經細胞暴露於磁場的時間愈久EPSPs以及APs增強的幅度愈大。
造成EPSPs以及APs強度增加的原因，可能是因為磁場造成神經細胞內鈣離子濃度增加所致，鈣離子的來源並非是來自於細胞外部而是由細胞內部儲存鈣離子的胞器釋出。細胞內部鈣離子濃度的增加會活化protein kinase A (PKA)及protein kinase C (PKC)等酵素，這些酵素進一步活化其下游的酵素，最後改變神經細胞的活性導致EPSPs以及APs強度增加。
磁場造成EPSPs與APs高度增加可能是透過增大離子的流量或是加大細胞膜的電阻值。量測lateral giant (LG)神經細胞在照射磁場期間其電流與電阻的變化情形，結果發現磁場並不影響電流大小但卻會造成細胞膜上的電阻值增大。
磁場造成EPSPs以及APs強度增加是在沒有頭胸部存在下產生的。在讓頭胸部存在之下，磁場所造成的EPSPs與APs增強的幅度減小了，而在沒有頭胸部存在的情況之下加入GABA(一種抑制性神經傳導物質)則可抑制磁場所造成的EPSPs增強。這似乎意味著磁場雖然會造成螯蝦逃跑神經的興奮，但在有頭胸部的存在下磁場亦會造成頭部神經興奮分泌更多的抑制性神經傳導物質，進而將尾部神經的興奮給抑制住了。
由於TEA可抑制細胞膜上的鉀離子通道，會造成全體細胞興奮性增強，將TEA加入螯蝦生理食鹽溶液中會發現LG的EPSP逐漸地變大，這種現象與靜磁場所引起的EPSP高度增加的情形極為類似, 而且在TEA存在下磁場無法讓EPSP更加增強, 所以磁場可能透過與TEA相同的作用途徑造成全體細胞興奮性增強。又因為我們在逃跑迴路中所測量的神經細胞都會對於靜磁場作出反應所以我們推測能感受到靜磁場的神經細胞是很多種類的並非只限定於特定的神經細胞。

The effects of static magnetic field on the crayfish escape circuit were studied. The static magnetic field was found to increase the amplitude of excitatory postsynaptic potentials (EPSPs) and action potentials (APs). The effect of static magnetic field on EPSPs was similar with APs. The increasing effects will be present until the exposure time of static magnetic field was enough.
The reasons for the enhancement of EPSPs and APs may be that the concentration of Ca2+ in the nerve cell was modulated by the presence of static magnetic fields. The Ca2+ might be released from the intracellular Ca2+ stores (mitochondria or ER). The increasing concentration of Ca2+ could activate the protein kinase A and protein kinase C. These enzymes could activate another enzyme and finally change the activity of nerve cell to cause the enhancement of APs and EPSPs.
The input resistance and current were measured when the static magnetic fields was present. We found that the static magnetic field could increase the input resistance but not the current.
When the K+ channel blocker (TEA) occurred in crayfish buffer, the induction of potentiation was not occurred. So the static magnetic field may influence the nerve cells through the route like the TEA to influence the K+ channel on the cell membrane.
Because the above experiments were done in the isolated abdomens preparation, the inhibition descending from more rostral ganglia of the crayfish CNS to the abdomen didn’t occur in this kind of preparation. In the semi-intact preparations, the inhibition descending from more rostral ganglia of the crayfish CNS to the abdomen occurred, and the potentiation of EPSPs was inhibited. These results imply that static magnetic fields could not only induce the potentiation of EPSPs in the abdomen nerve cells but also activate the nerve cells in the CNS of crayfish.

Abstract……………………………………………………………………………… 1
摘要………………………………………………………………………………… 2
前言………………………………………………………………………………… 3
材料與方法………………………………………………………………………… 5
結果………………………………………………………………………………… 15
一、 交流電磁場與直流電磁場可以使EPSP高度增加……………………… 15
二、 天然磁鐵所產生的靜磁場(SMF)也可以使EPSP高度增加……………… 18
三、 SMF在XYZ三個方向的分量磁場對於EPSP的增強都有貢獻………… 21
四、 靜磁場所導致的EPSP增強與磁場的方向性的關係……………………… 22
五、 靜磁場所導致的EPSP增強並非是由於GABA所誘發的抑制力量
減弱所致，可能與全體神經興奮性增加關 …………………………… 23
六、 只有electrical synapse 存在下靜磁場依然會造成EPSP的增強…………26
七、 靜磁場會影響突觸前神經細胞 ……………………………………………27
八、 靜磁場會影響突觸後神經細胞…………………………………………… 28
九、 靜磁場會使突觸後神經細胞膜電阻值變大但不會影響產生 action potential 電流的大小…………………………………………………29
十、 靜磁場與突觸後神經細胞內鈣離子的關係……………………………… 30
十一、 靜磁場也會影響其他的神經細胞 (MG) ,而且其影響的方式
與LG 相同…………………………………………………………………34
討論…………………………………………………………………………………36
參考資料……………………………………………………………………………38
致謝…………………………………………………………………………………40

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