Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo-SP, Brazil.
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo-SP, Brazil.
Proc Biol Sci. 2022 Jun 8;289(1976):20220799. doi: 10.1098/rspb.2022.0799. Epub 2022 Jun 15.
In nature, confrontations between conspecifics are recurrent and related, in general, due to the lack of resources such as food and territory. Adequate defence against a conspecific aggressor is essential for the individual's survival and the group integrity. However, repeated social defeat is a significant stressor promoting several behavioural changes, including social defence . What would be the neural basis of these behavioural changes? To build new hypotheses about this, we here investigate the effects of repeated social stress on the neural circuitry underlying motivated social defence behaviour in male mice. We observed that animals re-exposed to the aggressor three times spent more time in passive defence during the last exposure than in the first one. These animals also show less activation of the amygdalar and hypothalamic nuclei related to the processing of conspecific cues. In turn, we found no changes in the activation of the hypothalamic dorsal pre-mammillary nucleus (PMD) that is essential for passive defence. Therefore, our data suggest that the balance between the activity of circuits related to conspecific processing and the PMD determines the pattern of social defence behaviour. Changes in this balance may be the basis of the adaptations in social defence after repeated social defeat.
在自然界中，同种个体之间的对抗是经常发生的，通常是由于缺乏食物和领土等资源。个体的生存和群体的完整性需要有足够的防御能力来对抗同种的攻击者。然而，反复的社交挫败是一个重要的应激源，会促进多种行为变化，包括社交防御。这些行为变化的神经基础是什么？为了对此提出新的假设，我们在这里研究了重复的社交压力对雄性小鼠中与动机性社交防御行为相关的神经回路的影响。我们观察到，动物在第三次暴露于攻击者时，在最后一次暴露中比第一次暴露时花更多的时间处于被动防御状态。这些动物还显示出与同种线索处理相关的杏仁核和下丘脑核的激活减少。反过来，我们发现下丘脑背侧前乳突核（PMD）的激活没有变化，PMD 对于被动防御是必不可少的。因此，我们的数据表明，与同种处理相关的回路的活动和 PMD 之间的平衡决定了社交防御行为的模式。这种平衡的变化可能是重复社交挫败后社交防御适应性的基础。
