MPS 誘發 PTSD 樣小鼠模型之前額葉－杏仁核－海馬迴網路的動態重組

Abstract

摘要 創傷後壓力症候群（Post-Traumatic Stress Disorder, PTSD）是一種在個體經歷或目睹重大創傷事件後可能發生的精神疾病。雖然盛行率有限 (約3.9%) 但 當社會遭遇大規模創傷事件時但PTSD 的發生率往往顯著增加。 目前雖已有多種藥物被嘗試應用於PTSD治療但 多數僅能作為輔助治療但且通常需搭配認知行為治療（Cognitive Behavioral Therapy, CBT）方能有效改善症狀。因此但尋找更有效的治療策略仍是PTSD研究的重要課題。然而但越來越多研究指出但PTSD並非單純由特定受體、基因或神經元異常所造成但而是涉及多個腦區間神經網路功能的改變。因此但深入探討PTSD相關的神經迴路病理機制但將有助於未來治療藥物的開發與疾病理解。 在眾多與PTSD相關的神經迴路中但前額葉皮質（prefrontal cortex, PFC）、杏仁核（basolateral amygdala, BLA）與海馬迴（hippocampus, HPC）所構成的神經網路受到廣泛關注 。大研研究認為但前額葉杏杏仁核的由而而（（top-down）調控功能受損但可能是PTSD患者恐懼消退失敗的重要原因之一。然而但針杏PTSD相關神經迴路長期變化之研究仍相杏有限。 為了填補此研究缺口但本研究採用實驗室先前建立之 Multiple Prolonged Stress （MPS）模型進行探討。由於該模型過去主要應用於大鼠但因此本研究將進一步驗證MPS模型於小鼠中的適用性及其杏神經迴路功能之影響。本研究將電極分別植入PFC、BLA與HPC但以記錄局部場電位（local field potential, LFP）但並基於過去研究顯示θ振盪在恐懼相關行為中具有重要角色但進一步分析θ波功率、腦區間同步性及方向性連結之變化。 研究結果顯示但相較於傳統的 Single Prolonged Stress（SPS）模型但MPS 誘導之 PTSD 小鼠表現出獨特的神經迴路與θ波活動異常 。在創傷誘導後的期期階段但小鼠接收到與恐懼相關的提示音時但即出現顯著的神經迴路改變但包括 PFC 與 BLA 間θ同步性（降、PFC至BLA的方向性連結減弱但以及BLA的θ波功率顯著降低。此外但我們發現但在行為測試期間所發生的凍結事件 (freezing episodes) 中但凍結後短時間內的θ波功率強度與其凍結持續時間呈現弱負相關。然而但在創傷誘導至少一週後但而述由恐懼提示音所引發的神經迴路變化但以及θ波功率與凍結持續時間之間的負相關性皆不再存在 但而而之之的是腦腦區θ波功率的而升但呈現與傳統SPS模型相似的神經活動模式。此外但我們觀察到但由MPS所誘導的PFC至BLA方向性連結抑制在恐懼提示音呈現前即已存在但顯示此方向性連結受損可能具有長期持續性。 除了神經訊號分析之外但本研究亦進一步評估潛在治療策略 。過去研究指出但活化腺苷受體可抑制恐懼表達但然而但由於腺苷受體廣泛參與多種生理功能但直接活化可能限制其臨床應用。相較之（但抑制核苷轉運蛋白(Equilibrative nucleoside transporter 1, ENT1）可藉由提高胞外腺苷濃度但間接促進腺苷受體活化。本研究使用 ENT1抑制劑J4 。結果顯示但雖然 J4未能改善MPS所造成之神經迴路異常但 能有效逆轉異常（降的θ波功率 但同時降低凍結行為及焦慮表現。 總而言之 但本研究確認了MPS模型在神經迴路以及θ波活動而的獨特性 。MPS不僅杏PFC-BLA-HPC神經迴路造成更顯著且持續性的影響但亦呈現出不同於SPS的時間依賴性θ訊號變化。這些結果顯示但PTSD相關神經迴路的功能異常可能隨疾病進程而呈現不同的動態變化 但而MPS模型亦可能提供一個更貼近臨床PTSD神經病理特徵的動物模型但進而有助於PTSD神經迴路機制的解析及治療策略的開發。

Abstract Post-traumatic stress disorder (PTSD) is a psychiatric disorder that may develop after an individual experiences or witnesses a severe traumatic event. Although its overall prevalence is relatively limited, approximately 3.9%, the incidence of PTSD often increases markedly when society is exposed to large-scale traumatic events. Although various pharmacological treatments have been explored for PTSD, most currently available medications provide only adjunctive benefits and often need to be combined with cognitive behavioral therapy (CBT) to effectively improve symptoms. Therefore, identifying more effective therapeutic strategies remains an important goal in PTSD. However, increasing evidence suggests that PTSD is not caused simply by abnormalities in a single receptor, gene, or neuronal population, but rather involves functional alterations across neural networks connecting multiple brain regions. Thus, a deeper understanding of the circuit-level pathophysiology of PTSD may contribute to developing novel therapeutic strategies and improving our understanding of the disorder. Among the neural circuits associated with PTSD, the network comprising the prefrontal cortex (PFC), basolateral amygdala (BLA), and hippocampus (HPC) has received considerable attention. Numerous studies have suggested that impaired top-down regulation from the PFC to the amygdala may be one of the key mechanisms underlying impaired fear extinction in PTSD. However, studies investigating long-term alterations in PTSD-related neural circuits remain relatively limited. To address this gap, the present study employed a multiple prolonged stress (MPS) model previously established in our laboratory. Because this model has mainly been applied in rats, the present study further examined its applicability in mice and its effects on neural circuits. Electrodes were implanted into the PFC, BLA, and HPC to record local field potentials (LFPs). Based on previous evidence indicating an important role of theta oscillations in fear-related behaviors, we further analyzed changes in the theta power, interregional synchrony, and directional connectivity. The results showed that, compared with the traditional single prolonged stress (SPS) model, MPS-induced PTSD-like mice exhibited distinct abnormalities in neural circuits and theta activity. During the early phase after trauma induction, exposure to fear-associated cues induced significant circuit-level alterations, including decreased theta synchrony between the PFC and BLA, weakened directional connectivity from the PFC to the BLA, and a significant reduction in BLA theta power. In addition, during freezing episodes observed in behavioral testing, the theta power within a short period after freezing onset showed a significant negative correlation with freezing duration. However, at least one week after trauma induction, the cue-evoked circuit alterations and the negative correlation between theta power and freezing duration were no longer observed. Instead, theta power increased across the recorded brain regions, resembling the neural activity pattern observed in the traditional SPS model. Furthermore, the MPS-induced suppression of top-down (PFC → BLA) directional connectivity was already evident prior to the presentation of fear-associated cues, indicating that this impairment may persist long-term. In addition to neural signal analysis, this study also evaluated a potential therapeutic strategy. Previous studies have shown that activation of adenosine receptors can suppress fear expression. However, because adenosine receptors are widely involved in various physiological functions, direct receptor activation may limit clinical applicability. In contrast, inhibition of equilibrative nucleoside transporter 1 (ENT1) can indirectly promote adenosine receptor activation by increasing extracellular adenosine levels. In the present study, we used the ENT1 inhibitor J4. The results showed that although J4 did not rescue the MPS-induced circuit abnormalities, it effectively reversed the abnormal reduction in theta power and reduced freezing behavior and anxiety-like responses. In summary, this study demonstrates the distinct effects of the MPS model on neural circuit activity and theta oscillations. MPS not only induced more pronounced and persistent alterations in the PFC–BLA–HPC circuit but also produced time-dependent theta activity patterns that differed from those induced by SPS. These findings suggest that functional abnormalities in PTSD-related neural circuits may dynamically change over the course of disease progression. Moreover, the MPS model may provide an animal model that more closely reflects the neural pathophysiological features of clinical PTSD, thereby contributing to future investigations of PTSD circuit mechanisms and the development of novel therapeutic strategies.