三甲基甘胺酸和二甲基甘胺酸改善甲基安非他命所導致神經行為毒性

Abstract

甲基安非他命是一種被廣泛濫用的非法神經興奮劑，而且使用之後常伴隨著精神疾病的發生，動物研究也顯示，施打甲基安非他命所引起的神經毒性不僅會造成多巴胺神經元及血清素神經元的損傷，也引起認知功能和社交行為的缺失，同時對於產生迷幻作用的5-HT2A受體作用劑的行為反應增強。N,N,N-trimethylglycine (TMG)和N,N-dimethylglycine (DMG)是甘胺酸的甲基化衍生物，由於這兩種藥物具有治療神經系統疾病的潛力，因此本研究的目的為評估TMG及DMG是否可以預防或改善小鼠在甲基安非他命的暴露下所導致的行為缺失包括新位置辨識測試，新物體辨識測試，社交行為互動測試以及使用5-HT2A受體作用劑DOI 誘導小鼠頭部抽搐(head twitch )的行為。實驗方式為腹腔注射給予雄性ICR小鼠甲基安非他命，一天注射四劑（4 × 5mg/kg），每劑間隔兩小時。實驗一，小鼠在暴露甲基安非他命，先確認行為改變後，給予腹腔注射TMG及DMG (10或30 mg/kg)連續七天，評估TMG及DMG的治療效果。實驗二在施打每劑甲基安非他命30分鐘前給予TMG及DMG (100 mg/kg)，七天後進行行為評估，實驗三，評估TMG及DMG個別及混合劑量的治療效果，小鼠給予甲基安非他命之後，先確認行為改變，再給予腹腔注射TMG及DMG (20、5+5或是10+10 mg/kg) 連續七天，七天後進行行為測試。實驗四，檢測TMG及DMG的治療效果是否藉由活化NMDA受體glycine binding site，小鼠給予甲基安非他命七天之後，腹腔注射TMG及DMG (20 mg/kg)並在給予TMG及DMG前30分鐘給予glycine binding site 拮抗劑7-chlorokynurenic acid (7-CK) (1 mg/kg)，連續給藥七天，七天後進行行為評估。實驗結果發現連續給予七天TMG及DMG在個別劑量及混合劑量中都能夠恢復甲基安非他命所造成的認知功能缺損，社交退縮和降低由DOI 誘導小鼠頭部抽搐行為表現，以及在紋狀體中酪氨酸羥化酶的蛋白質表達減少情況。而前給予7-CK則阻斷TMG及DMG對甲基安非他命所造成的認知功能缺損，社交退縮的改善作用，但是對TMG及DMG對DOI 誘導小鼠頭部抽搐的行為的改善作用影響較小，顯示TMG及DMG可能都是經由活化NMDA 受體的glycine binding site改善甲基安非他命所造成的認知功能缺損，社交退縮，這些發現表示，TMG及DMG具有治療甲基安非他命成癮者所造成的精神分裂等異常症狀的潛力。

Methamphetamine (METH) is a widely abused illicit psychostimulant. METH use is commonly associated with psychosis. A neurotoxic regimen of METH, which damages the dopaminergic and serotonergic neurons, causes cognitive dysfunction, social interaction deficits, and supersensitivity to hallucinogen in mice. N,N,N-trimethylglycine (TMG) and N,N-dimethylglycine (DMG) are methyl derivatives of amino acid glycine and naturally occur as intermediate metabolites in choline-to-glycine metabolism. Growing evidence shows that both compounds have potential to treat some neurological disorders. The aim of this study was to examine the protective and therapeutic effects of TMG and DMG on METH-induced behavioral aberrations. The novel location recognition test (NLRT), the novel objective recognition test (NORT), the social interaction and the hallucinogenic 2, 5-dimethoxy-4-iodoamphetamine (DOI)-induced head twitch response were evaluated. Male ICR mice received one day drug treatment with four injections of METH (4 × 5 mg/kg, i.p.) or saline at 2h interval. First, TMG or DMG (10 or 30 mg/kg, i.p.) were separately administered once daily for seven consecutive days after the behavioral impairment was confirmed in METH-treated mice. Seven days after final injection of TMG and DMG, the behavioral tests were monitored. Secondly, the preveting effects of TMG and DMG were examined by TMG and DMG (100 mg/kg, i.p.) pretreatment, 30 min prior to each dose of METH. Third, the lower dose (20 mg/kg) and combined effects of TMG and DMG (5+5 or 10+10 mg/kg i.p.) were evaluated. Fourth, in order to determine if the improving effects of TMG and DMG are mediated by NMDA receptor glycine binding site, the glycine binding site antagonist 7-CK (1 mg/kg, i.p.) was administered 30 min prior to each dose of TMG and DMG (20 mg/kg, i.p.), TMG and DMG dose-dependently improved, but not prevented the METH-induced cognition deficits, social withdrawal and hypersensitivity to hallucinogen with additional effect. Pretreatment of 7-CK, reversed the improving effects of TMG and DMG on behavioral deficits after METH exposure, yet had minor effect on hypersensitivity to hallucinogen. These results demonstrate that TMG and DMG might activate the glycine binding site of NMDA receptor to improve METH-induced cognition deficits and social withdrawal. TMG and DMG may be the novel therapeutic agents for psychiatric disorders related to METH abuse.