Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
Laboratory of Herpetology, Butantan Institute, São Paulo, SP, Brazil.
Eur J Neurosci. 2022 Sep;56(6):4788-4802. doi: 10.1111/ejn.15794. Epub 2022 Aug 24.
We examined the behavioural responses and Fos expression pattern of rats that were exposed to snake threats from shed snakeskin and a live snake. We differentiated the behavioural responses and the pattern of Fos expression in response to the odour cues and mild threat from a live snake. Animals exposed to the snake odour alone or to the confined snake showed a great deal of risk assessment. Conversely, the intensification of odour during exposure to the live snake decreased the threat ambiguity, and the animals froze for a significantly longer period. Our Fos analysis showed that a pathway formed by the posteroventral part of the medial amygdalar nucleus to the central part of the ventromedial hypothalamic nucleus appeared to be solely responsive to odour cues. In addition, we showed increased Fos expression in a parallel circuit comprising the lateral amygdalar nucleus, ventral subiculum, lateral septum, and juxtadorsomedial region of the lateral hypothalamic area that is responsive to both the odour and mild threat from a live snake. This path is likely to process the environmental boundaries of the threat to be avoided. Both paths merge into the dorsal premammillary nucleus and periaqueductal grey sites, which all increase Fos expression in response to the snake threats and are likely to organize the defensive responses. Moreover, we found that the snake threat mobilized the Edinger-Westphal and supraoculomotor nuclei, which are involved in stress adaptation and attentional mechanisms.
我们研究了暴露于蛇蜕和活蛇的蛇威胁下的大鼠的行为反应和 Fos 表达模式。我们区分了对活蛇的气味线索和轻度威胁的行为反应和 Fos 表达模式。单独暴露于蛇气味或处于封闭蛇环境中的动物表现出大量的风险评估。相反，在暴露于活蛇时，气味的加剧降低了威胁的模糊性，动物会冻结更长时间。我们的 Fos 分析表明，由内侧杏仁核的后腹部分至腹内侧下丘脑核中央部分形成的途径似乎仅对气味线索有反应。此外，我们显示出在一个平行的电路中 Fos 表达增加，该电路包括外侧杏仁核、腹侧海马下脚、外侧隔核和外侧下丘脑的近腹侧区域，该电路对活蛇的气味和轻度威胁都有反应。这条路径可能处理需要避免的威胁的环境边界。这两个路径合并到背侧前乳头核和导水管周围灰质部位，这些部位都对蛇的威胁增加 Fos 表达，并可能组织防御反应。此外，我们发现蛇的威胁调动了参与应激适应和注意力机制的 Edinger-Westphal 和上丘核。
