臺灣博碩士論文加值系統

中文摘要 GABA(γ-氨基丁酸)為中樞神經系統主要的抑制性神經傳遞物質。GABAA受體由五個亞型單位組成，每一個亞型單位又呈現基因多型性(α1-6，β1-3，γ1-3，δ1，?1-3，ε1)，因此GABAA受體有很多的同源異構亞型體。由於GABAA受體的組成，大部份均含有β亞型單位，尤其是β2亞型單位，因此本實驗利用腦室內注射反意寡去氧核甘酸(antisense oligodeoxynucleotide , ASO)，選擇性的阻斷β2亞型單位的功能表達，企圖了解該受體結構和功能間的關係。大白鼠經腦室給予β2-ASO之後，在致痙攣劑引發痙攣的閾值方面， picrotoxin (氯離子通道阻斷劑) 引發的痙攣閾值相較於控制組，明顯降低了24 %。而bicuculline (GABAA受體拮抗劑)或β-CCM(methyl β-carboline-3-carboxylate，benzodiazepine之逆向致效劑) 引發的痙攣閾值則沒有改變。Strychnine(glycine受體拮抗劑) 引發的痙攣閾值，未受到β2- ASO的影響，在ASO及SO組均明顯上升，推論這可能是經腦室給予β2- ASO之後引發的非專一性的毒性反應。而picrotoxin引發痙攣閾值降低，bicuculline或β-CCM痙攣閾值卻未改變，顯示β2-ASO可能促使與picrotoxin有高度親合力的β3亞型單位大量取代，使得picrotoxin的致痙攣作用增強，痙攣閾值降低。另外，α1亞型單位蛋白質被影響的情形，在海馬迴區發現ASO及SO組α1蛋白質的量同時減少;下丘腦、紋狀體及大腦皮質則未有明顯變化，在海馬迴的作用可能也是β2-ASO造成的毒性反應。γ3 亞型單位蛋白質的量在下丘腦發現比控制組減少70 %，說明?2亞型單位功能不全，可能會使得γ3亞型單位結構發生改變。而β亞型單位在下丘腦的蛋白質量發現也減少60 %，我們則認為與?亞型單位基因相近的?3亞型單位，在β2-ASO之後也會發生變化。

英文摘要 GABA (γ-aminobutyric acid) is the major inhibitory transmitter in the CNS. GABAA receptor is a ligand-gated Cl- ion channel consisting of 5 homologus subunits derived from 5 separate gene families with multiple variants (α1-6, β1-3, γ1-3, δ1, ?1-3,ε1). Since most of the subtypes of GABAA receptor consists of β subunit, in particular β2 subunit, we have examined the effect of i.c.v. administration in rats of antisense oligodeoxynucleotide (ASO) to β2 subunit on receptor function. No behavioral effects were observed following β2 ASO treatment. The same treatment caused a significant 24% decrease in threshold dose for the convulsant effects of picrotoxin (a Cl- channel blocker). No change in sensitivity to the convulsant effect of bicuculline (a GABAA receptor antagonist) or β-CCM (methyl β-carboline-3-carboxylate, an inverse agonist) was found. However, an unexpected increase in seizure threshold for strychnine (a glycine receptor antagonist) induced tonus was found for rats treated with either sense or antisense oligodeoxynucleotide. This may be a nonspecific toxic response of i.c.v. oligodeoxynucleotide treatment. The selective alteration of convulsant threshold to picrotoxin but not bicuculline or β-CCM suggested that treatment with β2 ASO caused a specific change in the structure of GABAA receptors, resulting in the possible substation of β2 subunit with β3 with high affinity for picrotoxin. The expression of α1 in hippocampus was depressed in both ASO and SO treated animals, but was not altered in hypothalamus, striatum and cortex, suggesting a non-specific of oligodeoxynucleotide treatment. The protein levels of γ3 and β subunits were significantly decreased in hypothalamus, indicating β2 ASO treatment can alter the expression of other subunit in certain brain regions.

目 錄 目 錄 1 壹. 緒論 2 一. GABA的合成及代謝 2 二. GABA受體及其分類 4 三. GABAA受體的藥物結合位點 11 四. GABAA受體亞型單位的藥理作用 15 貳.研究目的 19 叁.實驗材料與方法 20 肆.結果 26 伍.討論 51 陸.附錄 58 柒.參考文獻 60

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