Carnevali Luca, Montano Nicola, Statello Rosario, Coudé Gino, Vacondio Federica, Rivara Silvia, Ferrari Pier Francesco, Sgoifo Andrea
Department of Chemistry, Life Sciences and Environmental Sustainability, Stress Physiology Lab, University of Parma, Italy.
Department of Internal Medicine, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, University of Milan, Italy.
Psychoneuroendocrinology. 2017 Aug;82:155-163. doi: 10.1016/j.psyneuen.2017.05.017. Epub 2017 May 20.
The negative emotional consequences associated with life stress exposure in an individual can affect the emotional state of social partners. In this study, we describe an experimental rat model of social stress contagion and its effects on social behaviour and cardiac autonomic and neuroendocrine functions. Adult male Wistar rats were pair-housed and one animal (designated as "demonstrator" (DEM)) was submitted to either social defeat stress (STR) by an aggressive male Wild-type rat in a separate room or just exposed to an unfamiliar empty cage (control condition, CTR), once a day for 4 consecutive days. We evaluated the influence of cohabitation with a STR DEM on behavioural, cardiac autonomic and neuroendocrine outcomes in the cagemate (defined "observer" (OBS)). After repeated social stress, STR DEM rats showed clear signs of social avoidance when tested in a new social context compared to CTR DEM rats. Interestingly, also their cagemate STR OBSs showed higher levels of social avoidance compared to CTR OBSs. Moreover, STR OBS rats exhibited a higher heart rate and a larger shift of cardiac autonomic balance toward sympathetic prevalence (as indexed by heart rate variability analysis) immediately after the first reunification with their STR DEMs, compared to the control condition. This heightened cardiac autonomic responsiveness habituated over time. Finally, STR OBSs showed elevated plasma corticosterone levels at the end of the experimental protocol compared to CTR OBSs. These findings demonstrate that cohabitation with a DEM rat, which has experienced repeated social defeat stress, substantially disrupts social behaviour and induces short-lasting cardiac autonomic activation and hypothalamic-pituitary-adrenal axis hyperactivity in the OBS rat, thus suggesting emotional state-matching between the OBS and the DEM rats. We conclude that this rodent model may be further exploited for investigating the neurobiological bases of negative affective sharing between social partners under chronic social stress conditions.
个体生活压力暴露所带来的负面情绪后果会影响社会伙伴的情绪状态。在本研究中，我们描述了一种社会应激传染的实验大鼠模型及其对社会行为、心脏自主神经和神经内分泌功能的影响。成年雄性Wistar大鼠成对饲养，其中一只动物（指定为“示范者”（DEM））在单独的房间里每天接受一次攻击性雄性野生型大鼠施加的社会挫败应激（STR），持续4天，或者仅暴露于一个陌生的空笼子中（对照条件，CTR）。我们评估了与经历STR的DEM大鼠同居对同笼伙伴（定义为“观察者”（OBS））的行为、心脏自主神经和神经内分泌结果的影响。在重复社会应激后，与CTR DEM大鼠相比，STR DEM大鼠在新的社会环境中测试时表现出明显的社会回避迹象。有趣的是，与CTR OBS相比，它们的同笼伙伴STR OBS也表现出更高水平的社会回避。此外，与对照条件相比，STR OBS大鼠在首次与STR DEM团聚后立即表现出更高的心率，并且心脏自主神经平衡向交感神经优势的转变更大（通过心率变异性分析来衡量）。这种增强的心脏自主神经反应性会随着时间而习惯化。最后，与CTR OBS相比，STR OBS在实验方案结束时血浆皮质酮水平升高。这些发现表明，与经历重复社会挫败应激的DEM大鼠同居会显著扰乱社会行为，并在OBS大鼠中诱导短暂的心脏自主神经激活和下丘脑 - 垂体 - 肾上腺轴亢进，从而表明OBS和DEM大鼠之间存在情绪状态匹配。我们得出结论，这种啮齿动物模型可进一步用于研究慢性社会应激条件下社会伙伴之间负面情感共享的神经生物学基础。
