長期給予母鼠嗎啡對其所生幼鼠腦中NMDA 受體亞型1A與2A的影響

Effect of chronic treatment ofmorphine on expression ofNMDA receptor in the developing rat

賴明成(Lai-ming-cherng)

指導教授 ： 葉健全

臺北醫學大學/醫學院/醫學科學研究所/碩士(2001年)

摘要

嗎啡在在臨床上是被用來作為止痛劑。但它的臨床作用經常被侷限於它易於產生藥物的依賴性及耐受性，一旦嗎啡被停用後即會產生令人難受的戒斷現象。嗎啡與它的衍生物如海洛因，常因受到濫用而造成成嚴重的社會問題。在如今婦女吸毒的比例也有增加的趨勢。若婦女在懷孕期間，依舊吸食嗎啡常會使其所生的下一代有不良的影響，在短期的症狀而言，有新生時的嗎啡脫癮症狀的產生與高死亡率。而長期而言，在出生後幾年其行為與學習常比正常的小孩來的遲緩，顯示了嗎啡對於腦部發育有一定程度的影響。因此對於預防新生兒嗎啡脫癮症狀以及瞭解嗎啡對於發育中的腦部所造成的毒性作用是非常重要的一個工作。過去本實驗室曾經發現嗎啡組的初生幼鼠在出生後第14天腦中大腦皮質以及海馬迴之N-methyl-D-aspartate receptor（NMDA receptor, 是一種興奮性氨基酸接受體之一）的密度與控制組相比在出生後第14天時有較低的情形，但此一情形到30天時則又回復正常。更進一步的利用西方墨點法則發現了嗎啡組在幼鼠出生後第7天及第14天其腦部各腦區的NMDA受體各個亞型皆有減量調控的情形但在第30天及60天時則沒有發生。為此我們推論長期給予母鼠嗎啡確實會導致其所生幼鼠腦中的NMDA受體亞型發生減量調控，然此一減量調控是因為含有NMDA受體的神經細胞數目的減少，還是只是因神經細胞上的NMDA受體亞型的表現量減少？因此本研究在相同的動物模式下，利用免疫組織染色法來計算這些幼鼠腦部在cortex、hippocampus CA1、hippocampus CA3、dentate gyrus、thalmus、mid brain、caudate putamen、global pallidus及accumbens nucleus各腦區含有NMDA受體亞型1A、2A的神經細胞數目並半定量其密度。結果我們發現在第7、14、30天的幼鼠在cortex、hippocampus CA1、hippocampus CA3、dentate gyrus、thalmus、mid brain、caudate putamen、global pallidus及accumbens nucleus 各腦區含有NMDA受體亞型1A與2A的神經細胞數目與正常幼鼠相較並沒有減少。但是卻可發現在PND7時嗎啡組的密度在cortex分別下降了69.7±11.3%及64.6±12.2%、而hippocampus CA1分別下降了74.7±10.1%、及65.6±11.3%，在hippocampus CA3與dentate gyrus的NR1A與NR2A則分別下降了72.6 ±13.1%與65.7±15.23%、caudate putamen分別下降34.6±11.1%、54.6±11.5% 而在accumbens nucleus則沒有差異而在PND14時嗎啡組在cortex分別下降了64.4±12.4%及54.3±10.1%、而hippocampus CA1分別下降了78.6±11.5%及77.6±21.4%，在hippocampus CA3與dentate gyrus的NR1A與NR2A則分別下降了62.3 ±14.8%與72.4±11.4%、caudate putamen分別下降32.6±14.2%、42.6±13.1% 。此結果與過去本實驗利用西方墨點法與受體結合實驗的結果相符合。由此可知長期暴露在嗎啡底下的幼鼠確實會造成其腦部cortex、hippocampus CA1、hippocampus CA3、dentate gyrus與caudate putamen等各區神經細胞上NR1A與NR2A的減量調控但此一減量調控並不會造成神經細胞的數目上的減少。

關鍵字

對位甲基左旋天門冬酸受體 ； 嗎啡 ； 新生幼鼠

並列摘要

Long-term neuropsychological abnormality has been documented in child born to morphine addicted mothers, but the mechanism of this phenomenon until now is not clear. Our previous studies found that ontogenic expression of the NMDA receptor in this rats is different to that of control rat by lacking an overshooting of NMDA receptor density on PND14.We also found that the expression of NMDA receptor subunit, namely, ( NR1A , NR2A , NR2B , NR2C ) proteins , in the cortex, hippocampus and striatum of morphine group rats is significantly less than at PND7 and PND14 as compare to that of control group. To further explore what kinds of NMDA receptor subunits are changed，our previous study had used western blotting to examine the expression of the NMDA receptor subunits . However we have known what kinds kinds of NMDA receptor subunits are changed but we still don’t know wheather the decrease of the NMDA subtypes’ expression on morphine group rats compared with normal group rats on PND7 and PND14 is from the decrease of the cell number of neuron having NMDA receptor or the expression of NMDA subuit in each neuron is decreased. To address this tissue we used immunohistochemistry to examine the immunoreactivity of NR1A、NR2A in the brain of rats born to morphine-treated dam rats. We found that the number of cell containing NR1A and NR2A in the region of cortex、hippocampus CA1、hippocampus CA3、dentate gyrus、thalmus、mid brain、caudate putamen、global pallidus and accumbens nucleus of morphine rats were not different to that of control rat. On the contrast , in the cortex、hippocampus CA1、hippocampus CA3、dentate gyrus、caudate putamen the density of NR1A and NR2A of morphine rats was dramatically decreased on PND7 and PND14 as compare to that of control group. These results demonstrated that that rats born to chronic morphine addicted dam rats induce downregulation of NMDA receptor subunits and does not cause the decrease of the cell number of neuron having NMDA receptor.

並列關鍵字

NMDA receptor ； morphine ； neonatal

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