安非他命對中樞神經NMDA受體之調控機制

The allosteric interaction of amphetamine with the N-methyl-D-

蔡秀娟(Hsiu-Chuan Tsai)

指導教授 ： 葉健全

臺北醫學大學/醫學院/天然物醫學研究所/碩士(1996年)

摘要

目前對於安非他命成癮及造成急慢性神經毒性的致病機制大都著重在與 多巴胺的釋放有關，然而有愈來愈多的證據顯示，安非他命成癮或導致長 期神經毒性，可被興奮性胺基酸及麩胺酸受體拮抗劑所阻斷，顯示麩胺酸 神經傳導系統在安非他命致病過程中扮演著重要角色．因此，我們利用受 體結合的方法來測試安非他命是否對麩胺酸次受體－NMDA受體有直接調控 作用．我們以[3H]glutamate測試安非他命在NMDA受體上NMDA結合處的作 用，[3H]glycine測試安非他命在glycine結合處的作用，及以[3H]TCP測 試安非他命在NMDA離子通道的作用．結果顯示安非他命可以抑制[3H]TCP 結合，其具有二處不同作用效價：一為高效價作用，抑制約15%的TCP結合 ，IC50為14.5+7.5nM；另一為低效價作用，抑制約89%的TCP結合，其IC50 為27.5+5.6uM，並且與TCP產生競爭性的結合抑制．同時，安非他命對[3 H]glycine結合亦具有競爭性抑制作用，其IC50為1.7+0.5uM，具有21%的 抑制作用．顯示安非他命對NMDA受體具有多重的調控機制．此外我們對大 白鼠重覆投與安非他命(5mg/kg)連續十四天，並在停藥後第一天，第七天 ，第十四天及第二十八天將大白鼠犧牲．[3H]TCP結果顯示，在停藥後第 十四天紋狀體NMDA受體對[3H]TCP結合的親合力下降，而大腦皮質區NMDA 受體之最大結合密度則上升．這項研究顯示長期給與安非他命可以調控 NMDA受體之表現，而這種改變可能是安非他命戒斷後造成慢性神經毒性的 致病機制之一．

關鍵字

安非他命 ； 成癮

並列摘要

Current idea of the mechanism by which amphetamine induces addiction as well as acute and long-term neurotoxicity is mainly focusing on the effect of dopamine release. However, recent evidences indicating that both amphetamine-induced addiction and long-term neurotoxicity can be prevented by excitatory amino acid receptor antagonists,suggestting an integral role for glutamate system in these processes. Therefore, we tested whether amphetamine could directly interact with the NMDA receptor, one subtypereceptor of glutamate receptor, using ligand binding to this receptor/channel complex. NMDA-displaced [3H]glutamate was used to bind the NMDA recognition sites;[3 H]glycine was used to bind glycine binding sites;and [3H]TCp was used to bind in the NMDA channel. Our binding data indicated that amphetamine inhibits NMDA-stimulated [3H]TCP with two potencies;a high potency effect which inhibits about 15% of TCP binding, the IC50 is 14.5+7.5nM;and a low potency effect which inhibits the other 89% of TCP binding,the IC50 is 27.5+5.6uM. Amphetamine simultaneously inhibits the binding of [3H]glycine binding,the IC50 is 1.7+0.5uM, which inhibits 21%of glycine binding,but had no effect on the binding of NMDA-displaced [3 H]glutamate. This result indicates a selective allosteric interaction of amphetamine administration can alter the expression of NMDA receptor. After 14 daily injection of d- amphetamine (5.0mg/kg),rats were sacrificed on the 1st, 7th, 14th, and 28th day. In cortex, the number of [3H]TCP binding wassignificantly increased in animals sacrificed 14 day and 28 day after the last d-amphetamine treatment. In striatum,the Kd of TCP binding was significantly inceased in animal sacrificed 14 day after the last -duamphrtamine treatment. The data suggestting a delayed up-regulation of the NMDA receptor may be one molecular mechanism of long-term neurotoxicity after withdraw of amphetamine in addicting patient.

並列關鍵字

NMDA受體 ； amphetamine ； NMDA receptor ； addiction