de Oliveira Crisanto Karen, de Andrade Wylqui Mikael Gomes, de Azevedo Silva Kayo Diogenes, Lima Ramón Hypolito, de Oliveira Costa Miriam Stela Maris, de Souza Cavalcante Jeferson, de Lima Ruthnaldo Rodrigues Melo, do Nascimento Expedito Silva, Cavalcante Judney Cley
Department of Morphology, Laboratory of Neuroanatomy, Biosciences Center, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
Department of Physiology, Laboratory of Neurochemical Studies, Biosciences Center, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
Physiol Behav. 2015 Dec 1;152(Pt A):272-9. doi: 10.1016/j.physbeh.2015.10.013. Epub 2015 Oct 22.
Studies from the last two decades have pointed to multiple mechanisms of fear. For responding to predators, there is a group of highly interconnected hypothalamic nuclei formed by the anterior hypothalamic nucleus, the ventromedial hypothalamic nucleus and the dorsal premammillary nucleus—the predator-responsive hypothalamic circuit. This circuit expresses Fos in response to predator presence or its odor. Lesion of any component of this system blocks or reduces the expression of fear and consequently defensive behavior when faced with a predator or its cue. However, most of the knowledge about that circuit has been obtained using the rat as a model of prey and the cat as a source of predator cues. In the present study, we exposed mice to strong cat or snake odors, two known mice predators, and then we used the rat exposure test (RET) to study their behavior when confronted with the same predator's odor. Our data point to a differential response of mice exposed to these odors. When Swiss mice were exposed to the cat odor, they show defensive behavior and the predator-responsive hypothalamic circuit expressed Fos. The opposite was seen when they faced snake's odor. The acute odor exposure was not sufficient to activate the mouse predator-responsive hypothalamic circuit and the mice acted like they were not in a stressful situation, showing almost no sign of fear or defensive posture. This leads us to the conclusion that not all the predator cues are sufficient to activate the predator-responsive hypothalamic circuit of mice and that their response depends on the danger that these predators represent in the natural history of the prey.
过去二十年的研究指出了恐惧的多种机制。为了应对捕食者，存在一组高度相互连接的下丘脑核团，由下丘脑前核、腹内侧下丘脑核和背侧乳头前核组成——捕食者反应性下丘脑回路。该回路在捕食者出现或其气味存在时表达Fos。该系统任何一个组成部分的损伤都会阻断或减少面对捕食者或其线索时恐惧的表达以及相应的防御行为。然而，关于该回路的大部分知识都是以大鼠作为猎物模型、猫作为捕食者线索来源获得的。在本研究中，我们将小鼠暴露于强烈的猫或蛇的气味中，这两种都是已知的小鼠捕食者，然后我们使用大鼠暴露试验（RET）来研究它们在面对相同捕食者气味时的行为。我们的数据表明暴露于这些气味的小鼠有不同的反应。当瑞士小鼠暴露于猫的气味时，它们表现出防御行为，捕食者反应性下丘脑回路表达Fos。而当它们面对蛇的气味时则相反。急性气味暴露不足以激活小鼠的捕食者反应性下丘脑回路，小鼠的行为就好像它们没有处于应激状态，几乎没有恐惧或防御姿态的迹象。这使我们得出结论，并非所有捕食者线索都足以激活小鼠的捕食者反应性下丘脑回路，它们的反应取决于这些捕食者在猎物自然史中所代表的危险程度。
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