探討壓力對於雌性小鼠觀察恐懼學習的影響;Investigate the effects of stress on female mice’s observational fear learning

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Title:	探討壓力對於雌性小鼠觀察恐懼學習的影響;Investigate the effects of stress on female mice’s observational fear learning
Authors:	李承豪;Lee, Cheng-Hao
Contributors:	生命科學系
Keywords:	早期壓力;不可預知壓力;恐懼社交轉移;基底外側杏仁核;腹側海馬迴;前扣帶皮層;性別差異
Date:	2024-08-20
Issue Date:	2024-10-09 15:28:40 (UTC+8)
Publisher:	國立中央大學
Abstract:	壓力為許多神經精神障礙的風險因子。恐懼社交轉移(social transfer of fear)是一種透過觀察他人恐懼表現進而導致個體自身同樣產生恐懼的學習過程，此能力的核心為能感受及分辨他人情緒的情緒同理心。同理心不但提供個體自我保護使個體不用親自接觸就能了解觀察到的情境並迴避對生存造成威脅的潛在危險環境或因子，同時也是社交認知中重要的一環。當他人遭遇艱困情境時，個體能夠正確理解他人情緒並結合情緒與情境的關係而進一步做出利他的行為。先前的研究發現，許多神經精神障礙患者會有辨別他人情緒和痛苦的能力缺陷，然而壓力是否影響恐懼社交轉移尚不清楚，尤其鮮少有足夠清晰的報告指出雌性動物的生理行為是否更容易受到賀爾蒙週期影響。在本論文中為了探討不同生命階段遭受的各種壓力是否會影響恐懼社交轉移，我們將雌性小鼠依照經歷的壓力類別區分成幼年早期壓力(Early life stress, ELS)以及成年慢性不可預測壓力(Chronic unpredictable stress, CUS)，並分成四組: 對照組(control)、早年壓力(ELS)、慢性不可預知壓力(CUS)以及雙重壓力(Double stresses, DS)。雌性小鼠在出生後第二天開始接受為期13天的早期生活壓力，並於成年後接受了為期14天的慢性不可預知壓力。我們發現有經歷慢性不可預知壓力的雌性小鼠產生體重下降以及腎上腺重量增加的現象，顯示雌性小鼠確實受到慢性不可預知壓力而產生生理變化。在恐懼社交轉移中，我們使從未經歷過壓力(Naïve)的陌生小鼠遭受電擊，並觀察上述四組雌性小鼠在電擊當下的行為表現。結果顯示經歷過雙重壓力的雌性小鼠比其他組別表現靜止不動的時間(freezing time)更短，顯示雙重壓力小鼠無法感受並陌生小鼠表現的恐懼情緒，也無法將恐懼情緒與情境形成聯想記憶，在觀察性恐懼學習能力上有缺失的現象。由於雌性小鼠缺乏相關的研究，我們進一步比對使用雄性小鼠研究的與恐懼社交轉移相關腦區的神經元活性，在恐懼社交轉移測試結束後，我們收取大腦組織並切片，利用免疫螢光染色技術並挑選c-Fos作為神經元的活性標記，探討壓力對這些相關腦區神經細胞的活化情形是否產生影響。我們觀察到在各組別的雌性小鼠在基底外側杏仁核(basolateral Amygdala，BLA)、腹側海馬迴(Ventral hippocampus，VHP)與前扣帶皮層(Anterior cingulate cortex，ACC)的c-Fos數量上都不具有統計上的顯著差異。根據上述結果，本研究顯示在雌性小鼠中壓力所引起的恐懼社交轉移缺失可能與雄性小鼠的相關腦區迴路無關或是存在性別差異。 ;Stress is a risk factor for many neuropsychiatric disorders. Social transfer of fear is a learning process where individuals develop fear by observing others′ fearful expressions. At the core of this ability is emotional empathy, which involves feeling and distinguishing others′ emotions. Empathy not only helps individuals protect themselves by understanding and avoiding potentially dangerous situations without direct personal contact, but it also plays a crucial role in social cognition. When others encounter difficult situations, individuals can correctly understand others. Emotions and the relationship between emotions and situations to further perform altruistic behaviors. Previous research has found that many patients with neuropsychiatric disorders have deficits in the ability to discern the feelings and pain of others. However, it is still unclear whether stress affects the social transfer of fear, and in particular, there are few clear reports indicating whether the physiological behavior of female animals is more susceptible to the hormone cycle. In this paper, to explore whether various stresses experienced at different life stages affect the social transfer of fear, we divided female mice according to the categories of stress they experienced. Early life stress (ELS) in adulthood and chronic unpredictable stress (CUS) in adulthood, and are divided into four groups: control, early life stress (ELS), chronic unpredictable stress (CUS), and Double stresses (DS). Female mice were exposed to 13 days of early life stress starting on the second day of life and 14 days of chronic unpredictable stress as adults. We found that female mice experiencing chronic unpredictable stress experienced weight loss and increased adrenal gland weight, indicating that female mice are indeed subjected to physiological changes caused by chronic unpredictable stress. In fear social transfer, we subjected strange mice that had never experienced stress (Naïve) to electric shock and observed the behavior of the above four groups of female mice under the electric shock. The results showed that female mice that had experienced double stress had shorter freezing time than other groups, indicating that the double-stressed mice were unable to feel the fearful emotions expressed by unfamiliar mice, and were unable to associate fearful emotions with the situation. The formation of associative memory and the lack of observational fear learning ability. Due to the lack of relevant research on female mice, we further compared the neuronal activity in brain areas related to fear social transfer using male mice. After the fear social transfer test, we collected brain tissue and sliced it, using immunofluorescence staining and selecting c-Fos as a marker of neuron activity to explore whether stress affects the activation of nerve cells in these related brain areas. We observed the amount of c-Fos in the basolateral amygdala (BLA), ventral hippocampus (VHP), and anterior cingulate cortex (ACC) of female mice in each group. There is no statistically significant difference. Based on the above results, this study shows that the lack of stress-induced fear social transfer in female mice may have nothing to do with the relevant brain circuits in male mice or there may be sex differences.
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