In humans the stress response is known to be modulated to a great extent by psychological factors, particularly by the predictability and the perceived control that the subject has of the stressor. This psychological dimension of the stress response has also been demonstrated in animals phylogenetically closer to humans (i.e. mammals). However, its occurrence in fish, which represent a divergent vertebrate evolutionary lineage from that of mammals, has not been established yet, and, if present, would indicate a deep evolutionary origin of these mechanisms across vertebrates. Moreover, the fact that psychological modulation of stress is implemented in mammals by a brain cortical top-down inhibitory control over subcortical stress-responsive structures, and the absence of a brain cortex in fish, has been used as an argument against the possibility of psychological stress in fish, with implications for the assessment of fish sentience and welfare. Here, we have investigated the occurrence of psychological stress in fish by assessing how stressor controllability modulates the stress response in European seabass (Dicentrarchus labrax). Fish were exposed to either a controllable or an uncontrollable stressor (i.e. possibility or impossibility to escape a signaled stressor). The effect of loss of control (possibility to escape followed by impossibility to escape) was also assessed. Both behavioral and circulating cortisol data indicates that the perception of control reduces the response to the stressor, when compared to the uncontrollable situation. Losing control had the most detrimental effect. The brain activity of the teleost homologues to the sensory cortex (Dld) and hippocampus (Dlv) parallels the uncontrolled and loss of control stressors, respectively, whereas the activity of the lateral septum (Vv) homologue responds in different ways depending on the gene marker of brain activity used. These results suggest the psychological modulation of the stress response to be evolutionary conserved across vertebrates, despite being implemented by different brain circuits in mammals (pre-frontal cortex) and fish (Dld-Dlv).

中文翻译：

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压力源可控性调节鱼类的压力反应

在人类中，已知压力反应在很大程度上受心理因素的调节，特别是受对象对压力源的可预测性和感知控制。这种应激反应的心理维度也已在系统发育上更接近人类的动物（即哺乳动物）中得到证实。然而，它在鱼类中的出现，代表了与哺乳动物不同的脊椎动物进化谱系，尚未确定，如果存在，将表明这些机制在脊椎动物中的深层进化起源。此外，在哺乳动物中，压力的心理调节是通过大脑皮层自上而下对皮层下压力反应结构的抑制控制来实现的，而鱼类缺乏大脑皮层，已被用作反对鱼类心理压力可能性的论据，对评估鱼类的感觉和福利有影响。在这里，我们通过评估压力源可控性如何调节欧洲海鲈（Dicentrarchus labrax）的压力反应来研究鱼类心理压力的发生。鱼暴露于可控制或不可控制的压力源（即有可能或不可能摆脱信号压力源）。还评估了失去控制的影响（可能逃跑，然后不可能逃跑）。行为和循环皮质醇数据都表明，与无法控制的情况相比，控制感降低了对压力源的反应。失去控制具有最不利的影响。硬骨鱼与感觉皮层 (Dld) 和海马 (Dlv) 同源物的大脑活动分别与不受控制和失去控制压力源平行，而侧隔 (Vv) 同源物的活动根据基因标记以不同的方式作出反应使用的大脑活动。这些结果表明，压力反应的心理调节在脊椎动物中是进化保守的，尽管哺乳动物（前额叶皮层）和鱼类（Dld-Dlv）的不同脑回路实施。