Cezario A F, Ribeiro-Barbosa E R, Baldo M V C, Canteras N S
Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
Eur J Neurosci. 2008 Sep;28(5):1003-15. doi: 10.1111/j.1460-9568.2008.06392.x. Epub 2008 Aug 8.
In this study we provide a comprehensive analysis of the hypothalamic activation pattern during exposure to a live predator or an environment previously associated with a predator. Our results support the view that hypothalamic processing of the actual and the contextual predatory threats share the same circuit, in which the dorsal premammillary nucleus (PMd) plays a pivotal role in amplifying this processing. To further understand the role of the PMd in the circuit organizing antipredatory defensive behaviors, we studied rats with cytotoxic PMd lesions during cat exposure and examined the pattern of behavioral responses as well as how PMd lesions affect the neuronal activation of the systems engaged in predator detection, in contextual memory formation and in defensive behavioral responses. Next, we investigated how pharmacological blockade of the PMd interferes with the conditioned behavioral responses to a context previously associated with a predator, and how this blockade affects the activation pattern of periaqueductal gray (PAG) sites likely to organize the conditioned behavioral responses to the predatory context. Behavioral observations indicate that the PMd interferes with both unconditioned and conditioned antipredatory defensive behavior. Moreover, we have shown that the PMd influences the activation of its major projecting targets, i.e. the ventral part of the anteromedial thalamic nucleus which is likely to influence mnemonic processing, and PAG sites involved in the expression of antipredatory unconditioned and conditioned behavioral responses. Of particular relevance, this work provides evidence to elucidate the basic organization of the neural circuits integrating unconditioned and contextual conditioned responses to predatory threats.
在本研究中，我们对暴露于活体捕食者或先前与捕食者相关的环境期间下丘脑的激活模式进行了全面分析。我们的结果支持这样一种观点，即下丘脑对实际捕食威胁和情境捕食威胁的处理共享同一神经回路，其中背侧乳头前核（PMd）在增强这种处理过程中起关键作用。为了进一步了解PMd在组织反捕食防御行为的神经回路中的作用，我们研究了在接触猫期间患有PMd细胞毒性损伤的大鼠，并检查了行为反应模式以及PMd损伤如何影响参与捕食者检测、情境记忆形成和防御行为反应的系统的神经元激活。接下来，我们研究了对PMd的药理学阻断如何干扰对先前与捕食者相关的情境的条件性行为反应，以及这种阻断如何影响导水管周围灰质（PAG）部位的激活模式，这些部位可能会组织对捕食情境的条件性行为反应。行为观察表明，PMd会干扰无条件和有条件的反捕食防御行为。此外，我们已经表明，PMd会影响其主要投射靶点的激活，即可能影响记忆处理的丘脑前内侧核腹侧部分，以及参与表达反捕食无条件和条件性行为反应的PAG部位。特别重要的是，这项工作为阐明整合对捕食威胁的无条件和情境性条件反应的神经回路的基本组织提供了证据。
