| 摘要: | 環境豐富化是藥物成癮的重要保護因子之一。本研究之目的是檢驗不同環境豐富化對於安非他安非他命誘導之行為敏感化及焦慮行為的影響。本研究首先確定最佳的環境豐富化條件（研究一），並透過多巴胺促進劑（即apomorphine）及拮抗劑（即haloperidol）檢驗最佳型態環境豐富化，對於安非他命誘導之行為敏感化及焦慮之減緩效果（研究二），最後驗證最佳環境豐富化型態在多巴胺投射路徑之可能（研究三）。本研究將區分四種環境豐富化（如社會環境豐富化、物理性環境豐富化、認知環境豐富化、以及標準環境豐富化），並且收集開放場域作業之行為指標，包含行為敏感化（如總距離、總速度、最大速度）與焦慮行為（如進出中心區的次數、時間、進入中心區的距離以及在中心區的速度）;同時，透過組織免疫染色方法（immunofluorescence, IHC）標定c-Fos（代表神經活性）在特定神經細胞核區——這些候選核區包括：cingulated cortex area 1 (Cg1), prelimbic cortex (PrL), infralimbic cortex (IL), basolateral amygdala (BLA), nucleus accumbens (NAc), striatum (e.g., caudate-putamen, CPu), CA1, CA3, dentate gyrus (DG)，以及ventral tegmental area (VTA)。並將透過光遺傳學，以AAV5-CaMKII-ChR2-EYFP 病毒檢驗IL投射NAc路徑，來確定參與環境豐富化緩解安非他命之行為敏感化的腦機轉。本研究發現標準環境豐富化的操弄是最佳的環境豐富化模式，可以減少安非他命誘導之行為敏感化，但安非他命在此研究中無法產生焦慮行為。此外，免疫染色的檢測結果發現，CA3, Cg1, DG, PrL, IL, BLA, NAc以及VTA核區得以產生較多的c-Fos表現量，代表這些核區參與安非他命誘導的行為敏感化。而標準環境豐富化操弄，可以使得CPu, Cg1, NAc, BLA, IL, VTA, CA3 及DG，這些核區的c-Fos表現量減少，代表標準環境豐富化操弄可以緩解安非他命誘導的行為敏感化及c-Fos表現量。另一方面，於VTA核區施打多巴胺促進劑及拮抗劑，兩者的控制組相比之下，多巴胺促進劑的施打產生更多活動量，表示多巴胺拮抗劑可能不影響動物的行為敏感化，但無論施打多巴胺促進劑或拮抗劑，標準環境豐富化仍可以減少安非他命誘導的行為敏感化。最後，光遺傳學數據表示，在環境豐富化下不論有無光線刺激，僅能降低動物行為距離，代表光刺激打在依核核區將減少行為敏感化，但是光刺激卻不影響焦慮行為。本研究結果將對於安非他命誘導的行為敏感化以及成癮，在臨床上，將帶來重要的臨床價值。;Environmental enrichment is an important protective factor for drug addiction. The purpose of this study is to examine the influence of different types of environmental enrichment on amphetamine-induced behavioral sensitization and anxiety behavior. This study first identified the optimal environmental enrichment (Study 1). Second, it investigated the effect of optimal environmental enrichment on amphetamine-induced behavioral sensitization and anxiety behavior using a dopamine agonist (apomorphine) and antagonist (haloperidol) (Study 2). Finally, the possible neural circuits involved in the environmental enrichment-mediated alleviation of amphetamine-induced behavioral sensitization were verified (Study 3). Four types of environmental enrichment (social, physical, cognitive, and standard) were examined, and open-field behavioral indices, including behavioral sensitization (total distance, total speed, and maximum speed) and anxiety behavior (the number, time, and distance of entries into the center area and the speed in the center area), were recorded. Immunofluorescence staining was used to label c-Fos (representing neural activity) in the candidate nuclei in the cingulate cortex area 1 (Cg1), prelimbic cortex (PrL), infralimbic cortex (IL), basolateral amygdala (BLA), nucleus accumbens (NAc), striatum (e.g., caudate-putamen, CPu), CA1, CA3, dentate gyrus (DG), and ventral tegmental area (VTA). In addition, optogenetics with AAV5-CaMKII-ChR2-EYFP virus was used to investigate the IL-NAc pathway to identify the brain circuits involved in the environmental enrichment-mediated alleviation of amphetamine-induced behavioral sensitization. The findings suggest that standard environmental enrichment manipulation is the optimal environmental enrichment model that reduced amphetamine-induced behavioral sensitization; however, amphetamine could not produce anxiety behavior. In addition, immunofluorescence staining revealed that CA3, Cg1, DG, PrL, IL, BLA, NAc, and VTA nuclei exhibited increased c-Fos expression, indicating that these nuclei were involved in amphetamine-induced behavioral sensitization. Standard environmental enrichment manipulation reduced c-Fos expression in the CPu, Cg1, NAc, BLA, IL, VTA, CA3, and DG nuclei, indicating that standard environmental enrichment can alleviate amphetamine-induced behavioral sensitization and c-Fos expression. A dopamine agonist and antagonist were injected into the VTA nucleus. Compared with the control group, the dopamine agonist increased activity, suggesting that the dopamine agonist may not affect the animals′ behavioral sensitization; however, standard environmental enrichment was still able to reduce amphetamine-induced behavioral sensitization regardless of the presence of a dopamine agonist or antagonist. Finally, the optogenetic data revealed that only the distance travelled was reduced under environmental enrichment, regardless of whether light stimulation was present or not, indicating that light stimulation on the IL nucleus can reduce behavioral sensitization but has no effect on anxiety behavior. The results of this study provide important clinical value to the knowledge of behavioral sensitization and addiction induced by amphetamine. |
