Université de Rennes 1, UMR CNRS 6552 Ethologie Animale et Humaine, Rennes, France.
PLoS One. 2012;7(6):e39280. doi: 10.1371/journal.pone.0039280. Epub 2012 Jun 28.
Recent reviews question current animal models of depression and emphasise the need for ethological models of mood disorders based on animals living under natural conditions. Domestic horses encounter chronic stress, including potential stress at work, which can induce behavioural disorders (e.g. "apathy"). Our pioneering study evaluated the potential of domestic horses in their usual environment to become an ethological model of depression by testing this models' face validity (i.e. behavioural similarity with descriptions of human depressive states).
METHODOLOGY/PRINCIPAL FINDINGS: We observed the spontaneous behaviour of 59 working horses in their home environment, focusing on immobility bouts of apparent unresponsiveness when horses displayed an atypical posture (termed withdrawn hereafter), evaluated their responsiveness to their environment and their anxiety levels, and analysed cortisol levels. Twenty-four percent of the horses presented the withdrawn posture, also characterized by gaze, head and ears fixity, a profile that suggests a spontaneous expression of "behavioural despair". When compared with control "non-withdrawn" horses from the same stable, withdrawn horses appeared more indifferent to environmental stimuli in their home environment but reacted more emotionally in more challenging situations. They exhibited lower plasma cortisol levels. Withdrawn horses all belonged to the same breed and females were over-represented.
CONCLUSIONS/SIGNIFICANCE: Horse might be a useful potential candidate for an animal model of depression. Face validity of this model appeared good, and potential genetic input and high prevalence of these disorders in females add to the convergence. At a time when current animal models of depression are questioned and the need for novel models is expressed, this study suggests that novel models and biomarkers could emerge from ethological approaches in home environments.
最近的综述对当前的抑郁症动物模型提出了质疑，并强调需要基于生活在自然环境中的动物来建立情绪障碍的行为模型。家养马会遭遇慢性压力，包括工作中的潜在压力，这可能会导致行为障碍（例如“冷漠”）。我们的开创性研究通过测试该模型的表面有效性（即与人类抑郁状态描述的行为相似性），评估了家养马在其通常环境中成为抑郁症行为模型的潜力。
方法/主要发现：我们观察了 59 匹工作马在其家庭环境中的自发行为，重点关注当马表现出异常姿势（此后称为“退缩”）时的静止不动期，评估了它们对环境的反应能力和焦虑水平，并分析了皮质醇水平。24%的马表现出退缩姿势，还表现出目光、头部和耳朵固定，这表明是一种自发的“行为绝望”表达。与来自同一马厩的对照“非退缩”马相比，退缩马在其家庭环境中对环境刺激表现出更为漠不关心，但在更具挑战性的情况下表现出更多的情绪化反应。它们的血浆皮质醇水平较低。所有退缩马都属于同一品种，且雌性马数量过多。
结论/意义：马可能是抑郁症动物模型的一个有用的潜在候选者。该模型的表面有效性似乎很好，而且这种障碍的潜在遗传因素和雌性的高患病率增加了其一致性。在当前的抑郁症动物模型受到质疑和需要新型模型的情况下，这项研究表明，新型模型和生物标志物可能会从家庭环境中的行为方法中出现。
