大白鼠重覆多次給予類鴉片物質對腦內delta類鴉片受體與興奮性胺基酸 NMDA受體表現的影響

The effect of chronic opioid treatment on the expression of delta opioid receptor and N-methyl-D-aspartate(NMDA) in rat brain

陳慧鈴(Huey-Ling Chen)

指導教授 ： 葉健全

臺北醫學大學/醫學院/細胞及分子生物研究所/碩士(1996年)

摘要

目前已知類鴉片的慢性給藥所產生的耐藥性 (tolerance) 常因此造成臨 床用藥的困擾，這些致病機轉至今仍然不清楚，有些學者認為可能與神經 細胞的類鴉片受體的數目變化有關。過去有報告指出重覆使用d類鴉片受 體的致效劑[D-Ala2, D-Leu5]enkephalin (DADLE) 會導致對此類鴉片產 生耐藥性，同時伴隨著d類鴉片受體的數目減少。而此受體數目減少的機 制，可能是此受體的轉錄作用受到抑制的結果。此外，有許多報告指出嗎 啡成癮的懷孕婦女容易產下學習或記憶方面不正常的嬰兒，而其病理機制 是否?V蚺漯滲姜g傳遞系統發生異常有關，值得進一步探討。在先前的N- methyl-D-aspartate (NMDA) 受體結合實驗中發現，長期接受嗎啡的母鼠 所生的幼鼠，其全腦區的NMDA受體數目在出生後14天與同天數的控制組比 較，顯示有30%的減少，而自體顯影分析結果以hippocampus (約47%)， amygdala (約40%)的減少最為顯著。此NMDA受體數目的減少有可能與基因 轉錄的抑制有關。綜合上述，本實驗的第一個目的在探討大白鼠重覆使用 DADLE之後，其d類鴉片受體發生的減量調控 (down-regulation) 是否起 因於d類鴉片受體mRNA的生成受到抑制所導致。實驗的第二個目的在探討 幼鼠在嗎啡長期使用下，其NMDA 興奮性胺基酸受體發生的減量調控是否 起因於NMDA受體mRNA的生成受到抑制所導致。因此我們使用原位雜交法 ( in situ hybridization ) 來定量d類鴉片受體mRNA與多種興奮性胺基酸 NMDA受體subunits mRNA在多處腦區的分佈與密度。我們的實驗結果顯示 大白鼠在DADLE慢性給藥後，d類鴉片受體mRNA的密度，只有在中腦區 midbrain於給藥三天後與控制組比較有短暫且明顯的減少，至於其他天數 與區域則沒有明顯的變化。顯示d類鴉片受體數目的減少與受體的轉錄作 用的變化無相關性。另外，在長期接受嗎啡的母鼠所生的幼鼠其各腦區 NMDAR (1A, 2A, 2B) mRNA的分佈密度，在出生後14天與控制組比較，並 沒有顯著的差異，只有在cortex和thalamus所含的NMDAR-2B mRNA與控制 組比較有明顯的減少。而在出生後30天的幼鼠其各腦區NMDA receptor (NMDAR) (1A, 2A, 2B) mRNA的分佈密度與同天數的控制組比較，均有顯 著的減少。這項結果顯示在接受嗎啡長期作用的母鼠所生的幼鼠，其腦部 NMDA受體數目的減少，並不與NMDA受體基因的轉錄變化有關。

關鍵字

耐藥性 ； 減量調控 ； 類鴉片受体 ； 興奮性胺基酸受體 ； 轉錄作用

並列摘要

Morphine tolerance is a major unsolved issue in analgesic clinics. Down-regulation of opioid receptor has been proposed as a mechanism underlying the generation of morphine tolerance. Previous report suggested that chronic treatment of [D-Ala2, D- Leu5]enkephalin (DADLE) induced a selective down-regulation of d opioid receptor (DOR) at the regions of cortex, midbrain and striatum in rat brain. This change in the d opioid receptor is paralleled with the development of tolerance to DADLE. In addition, the long-term neuropsychological sequels of children born to morphine-addicted woman has long been recognized in clinics. However, the pathological mechanism is still not comprehensive. Recent evidences indicate that the density of N- methyl-D-aspartate receptor (NMDAR) , a receptor plays an important role in developmental plasticity, in hippocampus and amygdala of rats born to morphine-treated dam rats is significant lower than the naive rats (control group) at P14 of post-natal age. To determine whether the decrease in the d opioid receptor and NMDA receptor is due to a decrease in the transcripts of gene encoding these receptors, we quantify the mRNA encoding NMDA receptors and DOR by oligonucleotides probe directed in situ hybridization. The result indicated no significant differences of DOR-1 mRNA in several brain regions between control and DADLE-treated rats except a transient decrease of DOR-1 mRNA in midbrain after 3-day treatment of DADLE. On the other hand, there was a significant decrease of NMDAR (1A, 2A, 2B) mRNA in several brain regions of rat born to morphine-treated dam rats (morphine group) at P30 of post-natal age as compared to that of control group. On the contrary, there was no significant differences of NMDAR (1A, 2A, 2B) mRNA between morphine group and control group at P14 of post-natal age except a transient decrease of NMDAR-2B mRNA at cortex and thalamus was seen in morphine group. These data indicated the decrease of DOR and NMDAR in DADLE-treated rats or rats born to morphine-treated dam rats is not due to a decrease in transcription of these receptors.

並列關鍵字

tolerance ； down-regulation ； opioid receptor ； NMDA receptor ； transcription