| Abstract: | 成鼠(或成人)腦中的神經新生到底有什麼功能? 大多數人的直覺認為神經新生是 有好處的，但就非常有限的科學研究顯示，無法對神經新生的功能下一結論。最近大 家開始嘗試思考將內生性神經新生應用於臨床治療，所以了解神經新生的功能是非常 重要的。在本研究中，主要要探討成鼠神經新生在恢復受損海馬迴功能中所扮演的角 色。 海馬迴是腦中負責學習與記憶的重要部位，也是許多神經疾病的發病點，像是阿茲 海莫症，失憶症，中風，癲癇，長期壓力等等。如果能找到方法來修復腦部的病變， 將可造福很多人。在成人或成鼠的大腦裡有兩個地方可以持續的進行神經細胞新生， 海馬迴的粒細胞是其中一個。之前我發展出一套雞尾酒治療方式(包含神經滋養分子， 神經生長分子， 以及豐富有刺激的環境)來促進神經細胞新生及生存，並恢復海馬迴 功能(Lai et. al., 2011a, submitted)。本計畫主要要利用這個我先前建立的系統來 了解神經新生功能。這個系統主要包括下列四部份: (1)一個可以引起漸進特定細胞死 亡的方式，(2)這些細胞的死亡造成某種行為能力喪失(3)可以次刺激神經細胞新生及 維持新細胞存活的物質(4)測試是否治療後腦部受損功能之恢復是由於腦中新細胞產 生。移除腎上腺可以很專一的造成海馬迴粒細胞死亡而不影響腦部任何其他區域，我 將以此作為研究系統配合上我先前研發的雞尾酒配方及行為操弄來進一步了解神經細 胞新生是否有助於恢復腦部功能及其可能的機制。 針對了解雞尾酒治療所引發的神經新生在受損腦恢復功能中所扮演的角色，本研究 計劃提出四個實驗方向: (1) 對雞尾酒治療所引發的神經新生作定性及定量分析，利 用螢光免疫染色及體視學螢光顯微鏡觀察新生神經細胞形態及數量， (2) 利用染料追 蹤方式來判斷新生神經細胞連結狀況，以及利用突觸標記染色來了解新生神經細胞是 否形成突觸， (3) 在動物進行學習記憶後利用BrdU(染新生細胞)及神經細胞抗體來標 定新生神經細胞，並觀察這些新生神經細胞是否表現神經細胞活動相關之immediate early gene，藉此了解是否新生神經細胞參與學習及記憶的過程， (4) 在雞尾酒治療 的同時抑制神經新生看是否雞尾酒治療仍然能恢復受損海馬迴功能，若功能無法恢 復，表示”神經新生”在雞尾酒治療後之海馬迴功能恢復扮演必要的角色。
Most people intuitively assume that adult born new neurons in the brain are beneficial and might provide a ways to actively improve brain function and cognition. The available experimental evidence is still too limited. To prove function of adult neurogenesis will be crucial to demonstrate the clinical importance of adult neurogenesis. But so far, very little has been achieved in this regard. This proposal aims to provide evidences for the roles of adult born neurons in functional recovery of damaged brain circuitry. The hippocampus is a brain region central to learning and memory and is a key target of many neurological diseases that have dramatic cognitive consequences, including Alzheimer’s and other forms of dementia, stroke, epilepsy, and chronic stress. Discovering methods that reverse damage would dramatically improve health for many people. Hippocampal granule cells are one of the two cell populations that produce new neurons continuously in adult mammalian brains. Previously, I established a simple mammalian model system for ablation and regeneration of specific neurons (granule cells) for studying the ability of regenerated neuron to restore cognitive and physiological functions of the hippocampus (Lai et. al. 2011a, b. submitted). There are four steps in the system: 1. A model where gradual hippocampal neuron death can be induced; 2. A method for characterizing the behavioral deficit associated with granule cell death; 3. Selection of substances and/or environmental stimulation that promotes generation of new neurons; 4. Assays for determining if the new neurons are responsible for restoring the function of lost neurons. By adrenalectomy (ADX) surgery, removal of adrenal glands, granule cells in the hippocampus were specifically eliminated. Because of corticosterone, an adrenal stress hormone, is essential for the survival of granule cells. After the degeneration of granule cells, a cocktail treatment will be applied to the animals to promote the regeneration of granule cells and restoration of functional brain circuitry (Lai et. al., 2011a submitted). Using this neuron degeneration-regeneration system in conjunction with behavior tests, one can try to determine if adult neurogenesis is critical for the repair of brain function. To understand the role of adult neurogenesis in the functional recovery of a damaged brain circuitry using the model I mentioned above, four steps are proposed to address this question. (1) Characterization of proliferation and morphology of neural progenitor cells and neurogenesis in the hippocampus after a cocktail treatment (2) Characterize the new circuitry and synapse formation after new granule cell integration in the hippocampus (3) Using neuron activity dependent immediate early gene expression as a marker for neuron activity. After the learning and memory test, in conjunction with BrdU(label new cells) and neuronal marker, one can determine if adult born neurons involved in the learning and memory process by checking if neuron activity dependent immediate early gene expressed in new neurons. (4) By blocking adult neurogenesis, provide evidences that the restoration of the hippocampal function depend upon new granule cells |
