以Akt1基因剔除小鼠為模式檢驗精神分裂症相關表現型以及AKT1對於多巴胺相關行為的影響

AKTing Up in Schizophrenia: Examination of Schizophrenia-related Phenotypes and the Involvement of AKT1 in Dopamine-dependent Behaviors Using Akt1 Knockout Mice

陳怡文(Yi-Wen Chen)

指導教授 ： 賴文崧

國立臺灣大學/理學院/心理學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.03050

摘要

精神分裂症是一種多因子且嚴重之精神疾患，從人類遺傳學及動物的研究中越來越多的證據顯示Akt1基因可能參與了精神分裂症的致病歷程。相較於以人類為受試所進行的遺傳相關性研究，基因突變小鼠的模式更能直接探究Akt1基因的生物功能以及它在精神分裂症致病性上之因果關係。本論文旨在以Akt1基因剔除小鼠為模式，探討AKT1在精神分裂症相關表現型以及多巴胺相關行為中之所扮演的角色。本論文的研究包含兩部份，在第一部份的研究中，Akt1基因剔除的公鼠與母鼠在一系列的基本行為測試中大多表現出正常的行為表現，然而相對於控制組，Akt1基因剔除母鼠在尾部懸吊試驗中靜止時間顯著較多，並且有較弱的前脈衝抑制驚跳反應。進一步檢驗與前脈衝抑制驚跳反應相關之聽覺皮質區的綠色螢光標定神經細胞也發現，Akt1基因剔除母鼠的神經細胞形態相較於控制組有顯著的不同。然而藥物測試結果顯示raclopride及clozapine這兩種抗精神分裂症藥物並不能扭轉Akt1基因剔除母鼠的前脈衝抑制驚跳反應缺損，但若使用AKT1下游GSK-3的抑制劑 8-OHDPAT或SB216763，則可以使Akt1 基因剔除母鼠的行為反應恢復到與控制組相近的水準。這部份的研究結果不僅顯示了Akt1基因的缺損的確會影響小鼠在前脈衝抑制驚跳反應的行為以及相關神經細胞形態的表現，且這樣的改變有性別上的差異，此外也凸顯了Akt1基因在多巴胺相關行為中以及藥物遺傳學上對於治療藥物選擇的重要性。在第二部份的研究則利用甲基安非他命引發的行為致敏化及佐以多巴胺類藥物注射為模式，進一步探討AKT1如何調節與多巴胺相關之訊息傳遞。實驗結果顯示，相較於控制組的公鼠，Akt1基因剔除公鼠對於甲基安非他命的致敏化較不敏感，但Akt1基因剔除母鼠和控制組母鼠相比則沒有差異。這樣的性別差異更進一步顯現在同時注射甲基安非他命及多巴胺D2受體致效劑或拮抗劑的甲基安非他命致敏化公鼠的行為，以及利用小動物正子造影技術及18F-FDG量測小鼠腦內紋狀體神經細胞活動情形 上，而甲基安非他命導致之小鼠腦內紋狀體神經細胞活動改變，在注射後的60到90分鐘更加明顯。有趣的是，Akt1基因剔除公鼠在行為致敏化模式下的自主活動量缺損可經由每日注射17β-estradiol的操弄所減緩。這些結果顯示AKT1對 於甲基安非他命致敏化所引發之過度活動的性別差異調控是具有區域性、時間性以及多巴胺D2受體專一性的。綜合以上兩個研究，本論文研究結果支持AKT1參與在多巴胺系統中，並且發現AKT1對多巴胺相關行為表現的影響具有性別上的差異，且雌性激素可能參與其中。

關鍵字

Akt1基因剔除小鼠 ； 性別差異 ； 前脈衝抑制驚跳反應 ； 抗精神分裂症藥物 ； GSK-3 抑制劑 ； 神經細胞形態 ； 甲基安非他命 ； 正子造影掃描

並列摘要

Schizophrenia appears to be a multifactorial disorder and accumulating evidence from human genetic and animal studies suggests that AKT1 (protein kinase Bα) might play certain roles in the pathogenesis of this disorder. Compared with human genetic studies, a mutant mouse model is a simple and relatively straightforward approach for determining the causal relationships and biological functions of AKT1 in the pathogenesis of schizophrenia. This master’s thesis aimed to study the roles of AKT1 in schizophrenia-related phenotypes and dopamine-dependent behaviors using AKT1 mutant mice as a model. In study 1, both male and female Akt1-/- mice displayed normal behavioral profiles in a battery of behavioral tasks but female mutant mice showed sex-specific alterations in immobility in the tail suspension test and in acoustic prepulse inhibition (PPI) compared with their wild-type (WT) controls. Female Akt1-/- mice also exhibited neuromorphological abnormalities in the GFP-labeled pyramidal neurons in the auditory cortex compared with those of the controls. Neither raclopride nor clozapine (antipsychotics) alleviated such PPI deficit in Akt1-/- females but it was mitigated by 8-OH-DPAT and SB216763 (indirect/direct Glycogen synthase kinase 3 (GSK3) inhibitors). The findings in study 1 not only reveal a sex-specific PPI deficit and related neuromorphological alterations in female Akt1-/- mice but also highlight the importance of AKT1 in the dopamine-dependent response and a pharmacogenetic effect of AKT1 on treatment selection. In study 2, the roles of AKT1 in the regulation dopamine signaling are further examined through methamphetamine (Meth)-induced behavioral sensitization and dopaminergic compound challenges. Male Akt1-/- mice were evident to be less sensitive to Meth-induced behavioral sensitization than their WT controls, whereas such genotypic reduction of hyperlocomotion did not appear in females mice. Such sex difference was further observed by co-injections of Meth with dopamine D2 receptor (DRD2) agonist/antagonist (i.e., quinpirole and raclopride) in Meth-sensitized mice and by measuring Meth-induced striatal brain activity using microPET with 18F-FDG, especially 60-90 min after Meth injection. Interestingly, the reduction of Meth-induced behavioral sensitization in Male Akt1-/- mice can be rescued by daily injections of 17β-estradiol. These results suggest a region-specific, temporal-specific and DRD2-specific sex difference of AKT1 in the regulation of Meth-related hyperactivity and estrogen might play some roles in this process. Taken all together, these findings support the involvement of AKT1 in the actions of dopamine and further indicate a sexually dimorphic effect of AKT1 in the regulation of behavioral phenotypes and DA-dependent responses, which might be affected by estrogen.

並列關鍵字

Akt1 mutant mice ； sex difference ； prepulse inhibition ； antipsychotics ； GSK-3 inhibitor ； neuromorphology ； methamphetamine ； PET scan

參考文獻

Chapter 1

Abi-Dargham, A., Mawlawi, O., Lombardo, I., Gil, R., Martinez, D., Huang, Y., et al. (2002). Prefrontal dopamine D1 receptors and working memory in schizophrenia. Journal of Neuroscience, 22, 3708-3719.

Arguello, P. A., & Gogos, J. A. (2006). Modeling Madness in Mice: One Piece at a Time. Neuron, 52, 179-196.

Baumeister, A. A., & Francis, J. L. (2002). Historical development of the dopamine hypothesis of schizophrenia. Journal of the History of the Neurosciences, 11, 265-277.

Brazil, D. P., & Hemmings, B. A. (2001). Ten years of protein kinase B signalling: a hard Akt to follow. Trends in Biochemical Sciences, 26, 657-664.