Threatened animals respond with appropriate defensive behaviors to survive. It has been accepted that midbrain periaqueductal gray (PAG) plays an essential role in the circuitry system and organizes defensive behavioral responses. However, the role and correlation of different PAG subregions in the expression of different defensive behaviors remain largely unexplored. Here, we designed and manufactured a microelectrode array (MEA) to simultaneously detect the activities of dPAG and vPAG neurons in freely behaving rats. To improve the detection performance of the MEAs, PtNP/PEDOT:PSS nanocomposites were modified onto the MEAs. Subsequently, the predator odor was used to induce the rat’s innate fear, and the changes and information transmission in neuronal activities were detected in the dPAG and vPAG. Our results showed that the dPAG and vPAG participated in innate fear, but the activation degree was distinct in different defense behaviors. During flight, neuronal responses were stronger and earlier in the dPAG than the vPAG, while vPAG neurons responded more strongly during freezing. By applying high-performance MEA, it was revealed that neural information spread from the activated dPAG to the weakly activated vPAG. Our research also revealed that dPAG and vPAG neurons exhibited different defensive discharge characteristics, and dPAG neurons participated in the regulation of defense responses with burst-firing patterns. The slow activation and continuous firing of vPAG neurons cooresponded with the regulation of long-term freezing responses. The results demonstrated the important role of PAG neuronal activities in controlling different aspects of defensive behaviors and provided novel insights for investigating defense from the electrophysiological perspective.

受到威胁的动物会做出适当的防御行为以求生存。人们普遍认为，中脑导水管周围灰质（PAG）在电路系统和组织防御行为反应中发挥着重要作用。然而，不同 PAG 亚区在不同防御行为表达中的作用和相关性在很大程度上仍未得到探索。在这里，我们设计并制造了微电极阵列（MEA）来同时检测自由行为大鼠中 dPAG 和 vPAG 神经元的活动。为了提高 MEA 的检测性能，将 PtNP/PEDOT:PSS 纳米复合材料修饰到 MEA 上。随后，利用捕食者气味诱导大鼠先天恐惧，检测dPAG和vPAG中神经元活动的变化和信息传递。我们的结果表明，dPAG 和 vPAG 参与先天恐惧，但在不同的防御行为中激活程度不同。在飞行过程中，dPAG 中的神经元反应比 vPAG 中的神经元反应更强、更早，而 vPAG 神经元在冻结过程中反应更强烈。通过应用高性能 MEA，揭示了神经信息从激活的 dPAG 传播到弱激活的 vPAG。我们的研究还表明，dPAG 和 vPAG 神经元表现出不同的防御放电特征，并且 dPAG 神经元以爆发放电模式参与防御反应的调节。vPAG 神经元的缓慢激活和持续放电与长期冻结反应的调节相一致。结果证明了 PAG 神经元活动在控制防御行为不同方面的重要作用，并为从电生理学角度研究防御提供了新的见解。