Cardiorespiratory adjustments that occur after feeding are essential to supply the demands of digestion in vertebrates. The well-documented postprandial tachycardia is triggered by an increase in adrenergic activity and by non-adrenergic non-cholinergic (NANC) factors in mammals and crocodilians, while it is linked to a withdrawal of vagal drive and NANC factors in non-crocodilian ectotherms—except for fish, in which the sole investigation available indicated no participation of NANC factors. On the other hand, postprandial ventilatory adjustments vary widely among air-breathing vertebrates, with different species exhibiting hyperventilation, hypoventilation, or even no changes at all. Regarding fish, which live in an environment with low oxygen capacitance that requires great ventilatory effort for oxygen uptake, data on the ventilatory consequences of feeding are also scarce. Thus, the present study sought to investigate the postprandial cardiorespiratory adjustments and the mediation of digestion-associated tachycardia in the unimodal water-breathing teleost Oreochromis niloticus . Heart rate ( f H ), cardiac autonomic tones, ventilation rate ( f V ), ventilation amplitude, total ventilation and f H / f V variability were assessed both in fasting and digesting animals under untreated condition, as well as after muscarinic cholinergic blockade with atropine and double autonomic blockade with atropine and propranolol. The results revealed that digestion was associated with marked tachycardia in O. niloticus , determined by a reduction in cardiac parasympathetic activity and by circulating NANC factors—the first time such positive chronotropes were detected in digesting fish. Unexpectedly, postprandial ventilatory alterations were not observed, although digestion triggered mechanisms that were presumed to increase oxygen uptake, such as cardiorespiratory synchrony.

中文翻译：

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尼罗罗非鱼（Oreochromis niloticus）餐后心肺反应和消化相关性心动过速的调节

进食后发生的心肺调节对于满足脊椎动物的消化需求至关重要。有据可查的餐后心动过速是由哺乳动物和鳄鱼的肾上腺素能活性和非肾上腺素非胆碱能 (NANC) 因子的增加引发的，而它与非鳄鱼变温动物的迷走神经驱动和 NANC 因子的退出有关——除了鱼类，其中唯一可用的调查表明没有 NANC 因素的参与。另一方面，呼吸空气脊椎动物的餐后通气调整差异很大，不同物种表现出过度换气、换气不足，甚至根本没有变化。对于生活在氧容量低的环境中的鱼，需要很大的通风才能吸收氧气，关于喂养对通气影响的数据也很少。因此，本研究试图调查单峰吸水硬骨鱼 Oreochromis niloticus 的餐后心肺调节和消化相关心动过速的调节。在未经治疗的情况下，以及在毒蕈碱胆碱能阻滞后，在禁食和消化动物中评估心率 ( f H )、心脏自主神经张力、通气率 ( f V )、通气幅度、总通气量和 f H / f V 变异性阿托品和阿托品和普萘洛尔双重自主神经阻滞。结果表明，消化与尼罗罗非鱼明显的心动过速有关，由心脏副交感神经活动的减少和循环的 NANC 因子决定——这是第一次在消化鱼中检测到这种阳性变时性物质。出乎意料的是，没有观察到餐后通气改变，尽管消化触发了被认为会增加摄氧量的机制，例如心肺同步。