Abstract
摘要:精神分裂症(schizophrenia)的盛行率在全世界人口中約為1%,是一種造成家庭與社會沉重負擔的重大精神疾患,但是目前對於精神分裂症之致病機轉及可能成因仍然不清楚。從人類遺傳學及神經科學的研究中發現精神分裂症很可能是多基因遺傳的疾病,並發現NRG1等基因是可能致病的遺傳因子之一,非常值得深入研究。然而從同卵雙生子的研究中也發現雙生子的精神分裂症共病率從未超過百分之五十,顯示後天環境因子對於精神分裂症可能扮演一定的調控角色。同時從公共衛生與臨床的研究中發現精神分裂症通常好發於青春期,也發現女性患者的發病時間通常較男性患者晚,從這些臨床觀察資料以及研究發現中可以推測雌性激素對於精神分裂症罹病可能扮演某種保護的角色,同時青春期階段的心理與社會壓力很可能進一步促成精神分裂症之症狀的出現與惡化,特別是在帶有基因缺損的群體或是個人之中。為了進一步驗證後生論的這個假說,在這個子計畫中特別針對精神分裂症的候選基因NRG1並以NRG1基因缺損小鼠為模式,去探討壓力與性激素對於小鼠在與精神分裂症症狀相關之行為測驗以及神經活動的表現,這些作業包括了前脈衝抑制、痕跡恐懼制約與社會記憶等作業,藉以當作評估精神分裂症三個重要症狀(即注意力、認知能力以及社交能力缺損)的動物模式。在這個計畫中,壓力的操弄採用了心理壓力與社交壓力這兩個兼具生態校度與病原校度的壓力源,在心理壓力的部分將給予電擊與中性聲音或環境連結的制約學習後並用該中性刺激的重複呈現作為心理壓力源;在社交壓力的部分會將受試小鼠與具攻擊性的優勢鼠配對飼養於同一籠內十天以期產生有效地社交壓力,在我們目前初步的實驗中已經發現NRG1小鼠的社會再認能力有缺損的現象。在性激素調控的部分,將利用手術閹割/卵巢切除及睪固酮/雌性激素的注射來分別調控雄性與雌性小鼠青春期發展階段體內雄/雌性激素含量,同時將進一步結合這些壓力與性激素的操弄去研究是否會在NRG1基因缺損的小鼠中有促發或舒緩精神分裂症相關症狀的效果。在這個子計畫中將利用NRG1基因缺損小鼠為模式去探討以下八個主要目標:(1)評量心理/社交壓力對於精神分裂症致病性及行為的影響;(2)利用神經毀除法研究壓力所引發之情緒改變的行為以及神經機制(3)評估發展過程中性激素對於精神分裂症的促發所扮演的調控角色;(4)研究壓力及性激素兩種因素對於大腦神經電生理活動的影響;(5)用離體電生理的方法去研究壓力及性激素對於神經突觸活動的影響;(6)透過與GFPm品系小鼠交配以及神經染色方法檢驗小鼠大腦神經形態與結構改變;(7)利用動物正子斷層掃瞄儀與動物核磁斷層掃瞄儀去檢驗壓力及性激素對於特定腦區結構與大腦神經活動之影響;(8)利用藥物之專屬性研究藥物對於RNG1小鼠之行為與神經機制的改變。
Abstract: Schizophrenia is a devastating psychiatric disorder and affects approximately 1 percent of the worldwide population during their lifetime. Schizophrenia is found all over the world, however, the etiology of schizophrenia is still unknown. Accumulating evidence from human genetics and neuroscience studies has started to merge and suggest several positional candidate loci and functional candidate genes, including neuregulin 1 (NRG1). While evidence indicates a genetic basis for schizophrenia, the concordance rate in homozygotic twins inflicting schizophrenia never reaches 50%, suggesting epigenetic involvement in this disease. In view of appearance of major schizophrenic symptoms after the juvenile stage, it is conjectured that psychological or social stress encountered at the puberty may be a factor of precipitating the symptoms in a genetic prone population. To test the hypothesis of epigenesis of schizophrenia, construction of mice with targeted mutations in NRG1 is a preferable model to identify functional significance of the NRG1 with etiology validity and it can be further subjected to environmental insults (i.e. stress or reproductive hormonal manipulations) to elucidate the potential interactions between gene and stress/hormone especially during developmental process. A new line of heterozygous NRG1 knockout mice and their wild-type littermate controls will be subjected to stress or hormonal manipulations and then tested on pre-pulse inhibition, trace fear conditioning and social memory tests, which are used to model the attention, cognitive and social or emotional impairments in schizophrenic patients. Considering ecological and etiological validities, psychological and social stress will be applied in our experiments. Psychological stress will be induced by pairing an otherwise neutral stimulus with a foot shock, while social stress will be induced by group housing of each subject with an aggressive resident mouse for 10 days. Our preliminary data suggest that the NRG1 mutants have normal sociability but somehow impair in their ability of social recognition. It is expected that psychological or social stress will either precipitate or aggravate behavioral deficits in the mutant mice which are sexually matured. Further, reproductive hormones may play an enabling role in these deficits, thus gonadectomy before stress should be able to attenuate the effects of stress on the various behavioral indices. Findings from this project should contribute to our understanding of how external factors in the environment or internal milieu in the body interact with genetic endowment to induce symptoms of schizophrenia. This project is expected to achieve eight specific aims: (1) To assess the effects of psychological or social stress on the behavioral tasks of schizophrenia-like phenotypes (i.e. pre-pulse inhibition, trace fear conditioning and social memory) in NRG1 mutant mice. (2) Using lesion techniques to reveal the anatomical and neural mechanisms underlying stress-induced behavioral changes, especially the sensory-motor function. (3) To evaluate the effects of gonad hormone depletion and supplement on behavioral and cognitive functions in the mice with/without stress. (4) To study the neurophysiological correlates of the stress or hormonal effects on the tasks of schizophrenia-like phenotypes in behaving mice. (5) To study the synaptic mechanisms underlying neurophysiological correlates of the stress and hormonal effects in brain slices or reduced preparation of NRG1 mutant mice. (6) To investigate neural morphology in the brains of mutant mice using the GFP-m mouse line and staining methods. (7) To visualize brain activity in vivo using micro-PET and animal MRI. (8) To study the regulatory effects of drugs on behavioral and neurobiological changes in mutant mice.
Keyword(s)
精神分裂症
NRG1 小鼠
認知功能
神經形態學
內生表現型
生殖賀爾蒙
壓力
schizophrenia
NRG1 mice
cognitive function
neural morphology
endophenotypes
behavioral phenotyping
gonad hormone
stress