Previous studies showed that the dorsal premammillary nucleus of the hypothalamus (PMD) is involved in social passive defensive behaviors likely to be meditated by descending projections to the periaqueductal gray (PAG). We focused on the rostral dorsomedial PAG (rPAGdm) to reveal its putative neural mechanisms involved in mediating social defensive responses. By combining retrograde tracing and FOS expression analysis, we showed that in addition to the PMD, the rPAGdm is influenced by several brain sites active during social defeat. Next, we found that cytotoxic lesions of the rPAGdm drastically reduced passive defense and did not affect active defensive responses. We then examined the rPAGdm's projection pattern and found that the PAGdm projections are mostly restricted to midbrain sites, including the precommissural nucleus, different columns of the PAG, and the cuneiform nucleus (CUN). Also, we found decreased FOS expression in the caudal PAGdm, CUN, and PMD after the rPAGdm was lesioned. The results support that the rPAGdm mediates passive social defensive responses through ascending paths to prosencephalic circuits likely mediated by the CUN. This study provides further support for the role of the PAG in the modulation of behavioral responses by working as a unique hub for influencing prosencephalic sites during the mediation of aversive responses.

中文翻译：

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导水管周围灰质头侧背内侧柱在大鼠社交失败中的作用


先前的研究表明，下丘脑乳头背侧核（PMD）参与社会被动防御行为，可能是通过向下投射到导水管周围灰质（PAG）来冥想的。我们关注头侧背内侧 PAG (rPAGdm)，以揭示其参与调节社会防御反应的假定神经机制。通过结合逆行追踪和 FOS 表达分析，我们发现除了 PMD 之外，rPAGdm 还受到社交失败期间活跃的几个大脑部位的影响。接下来，我们发现 rPAGdm 的细胞毒性损伤大大减少了被动防御，但不影响主动防御反应。然后我们检查了 rPAGdm 的投影模式，发现 PAGdm 投影主要局限于中脑部位，包括前连合核、PAG 的不同列和楔形核 (CUN)。此外，我们发现 rPAGdm 损伤后尾部 PAGdm、CUN 和 PMD 中 FOS 表达降低。结果支持 rPAGdm 通过上行路径介导可能由 CUN 介导的前脑回路，从而介导被动的社会防御反应。这项研究通过在厌恶反应的调解过程中作为影响前脑部位的独特枢纽，为 PAG 在行为反应调节中的作用提供了进一步的支持。