In congestive heart failure (CHF), while resting parasympathetic activity becomes reduced, parasympathetically-mediated responses to stressors have not been described. This study aimed to (1) elucidate the effect of CHF on fear bradycardia, a parasympathetically-mediated response, and (2) examine if brain oxidative stress of CHF mediates fear bradycardia. White noise sound (WNS) exposure to conscious rats induced freezing behavior and elicited bradycardia. WNS exposure-elicited bradycardia was greater in rats with CHF than in controls. Superoxide dismutase mimetics administered in the lateral/ventrolateral midbrain periaqueductal gray (l/vlPAG), a region that contributes to the generation of fear bradycardia, had no effect on the bradycardia response in control and CHF rats. Dihydroethidium staining in situ showed that superoxide generation in the l/vlPAG of CHF rats was increased as compared to controls. These results demonstrate that CHF leads to the augmentation of fear bradycardia. Moreover, oxidative stress in the l/vlPAG of CHF unlikely mediates the augmented fear bradycardia.

中文翻译：

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心力衰竭大鼠的恐惧感增强，心动过缓。


在充血性心力衰竭（CHF）中，虽然静息时副交感神经活动减少，但副交感神经介导的对应激源的反应尚未被描述。本研究旨在 (1) 阐明 CHF 对恐惧心动过缓（一种副交感神经介导的反应）的影响，以及 (2) 检查 CHF 的脑氧化应激是否介导恐惧心动过缓。白噪声（WNS）暴露于清醒的大鼠中会诱发僵直行为并引起心动过缓。患有 CHF 的大鼠中 WNS 暴露引起的心动过缓比对照组更严重。在外侧/腹外侧中脑导水管周围灰质（l/vlPAG）（一个有助于产生恐惧性心动过缓的区域）施用超氧化物歧化酶模拟物，对对照和 CHF 大鼠的心动过缓反应没有影响。原位二氢乙锭染色显示，与对照组相比，CHF 大鼠的 l/vlPAG 中的超氧化物生成增加。这些结果表明，CHF 会导致恐惧性心动过缓的加剧。此外，CHF 的 l/vlPAG 中的氧化应激不太可能介导增强的恐惧性心动过缓。