中腦至皮質及邊緣系統的多巴胺被認為是主導個體對酬賞的主觀感受(包括自然界的酬賞物質及上癮的藥物)，它並且支配與酬賞有關的行為學習增強歷程。唯這個多巴胺系統是如何主導上述行為功能仍有疑慮且值得再行探究，既使已有很多証據顯示拮抗或破壞多巴胺會導致行為表現受損，但進一步去確認這個腦與行為關係的議題是極重要的研究工作。本研究建置跑爬跑行為作業去探討之，它是一種新的且敏感的行為測試工具。紋狀體、依核、內側前額葉皮質是這個系統軸突終端聯會區，它們應對這種可操作不同作業要求的行為工具有不相等的機制參與其中。因之，本研究的目的即在於驗証這個多巴胺系統影響或參與跑爬跑行為的神經行為機制。這行為工具被設計成探討不同的行為內涵，包括利用不等的爬繩長度反映行為成本，利用不等質量的酬賞物反映增強誘因的利益，及成本與利益兩因子的交互作用。另外，這行為工具亦可進行制約增強的實驗步驟；更特別的是其可以反映一種經由成本利益分析的行為反應分配或選擇的內涵，即對以高成本行為反應得到高利益酬賞之選項有反應的偏好傾向。這些是不同行為內涵的跑爬跑作業被有效的建置後，本計畫利用神經毒物破壞前述多巴胺軸突終端區，以驗証這些區域的參與機制為何。實驗結果發現依核（而非背側紋狀體）參與成本利益分析的跑爬跑選擇行為，另外相似的結果也發現在背側前額葉皮質（而不是腹側前額葉皮質）。另外，本研究進一步建立一種風險選擇行為，以進一步佐證多巴胺與成本利益分析的關係。本研究亦藉由Fos 蛋白質免疫分析法，檢驗不同行為作業內涵對大腦神經細胞的活性之影響，結果發現在多巴胺系統的相關部位確實有相對應的反應。 The mesocorticolimbic dopamine (DA) system is known as the best candidate for the common neural substrate for mediating the subjective rewarding action of natural rewards and drug of abuse, and also for playing a critical role in the maintenance of reinforcement process. However, how exactly the DA exerts its functions in this brain system for reward-motivated behavior remains uncertain and in debate. Despite considerable evidence showing behavioral impairment under DA antagonism or lesion, it is important to be more precise on parsing the relationship between behavior and brain on this issue. This project set up a sensitive and newly developed measure so-called run-climb-run (RCR) behavioral task to encounter this challenge. It was reasonably presumed that different terminal areas of this DA system are differentially are involved in distinct requirements on RCR behavioral task. As focusing on such a theme, this project aims to investigate the neurobehavioral mechanisms of mesocorticolimbic DA system by the use of RCR behavioral task. This 3-year project was designed to reveal the effects of DA antagonism on several different behavioral components of the RCR task. The behavioral components were measured by manipulating 1) solely on the rope length to determine the response cost required for completing behavior, 2) solely on the reward value of reinforcer to judge the earned benefit, and 3) the interaction between cost and benefit by holding one factor in consistent and varying the other. Another behavioral manipulation was focused on establishing the concurrent choice paradigms based on selecting either high/cost to get high/benefit or low/cost to get low/benefit. Following the establishment of these different tasks on RCR behavior, neurotoxic lesions made in the striatum, the nucleus accumbens (NAC), and medial prefrontal cortex (mPFC) were conducted to determine the role of DA terminal areas involved. The results show the NAC (but not the dorsal striatun) was involved in the present task, such role was also confirmed to dorsal mPFC (but not ventral mPFC). Moreover, the present work further set up a risky choice behavior to determine the core component of cost/benefit analysis in choice. By the use of Fos-like assay, the immunoreactivity tested from several regions within the mesocorticolimbic DA system were correlated with the different requirements on RCR behavior.