Coronary perfusion and cardiac autonomic regulation may benefit myocardial oxygen delivery and thermal performance of the teleost heart, and thus influence whole animal heat tolerance. Yet, no study has examined how coronary perfusion affects cardiac output during warming in vivo. Moreover, while β-adrenergic stimulation could protect cardiac contractility, and cholinergic decrease in heart rate may enhance myocardial oxygen diffusion at critically high temperatures, previous studies in rainbow trout (Oncorhynchus mykiss) using pharmacological antagonists to block cholinergic and β-adrenergic regulation showed contradictory results with regard to cardiac performance and heat tolerance. This could reflect intra-specific differences in the extent to which altered coronary perfusion buffered potential negative effects of the pharmacological blockade. Here, we first tested how cardiac performance and the critical thermal maximum (CTmax) were affected following a coronary ligation. We then assessed how these performances were influenced by pharmacological cholinergic or β-adrenergic blockade, hypothesising that the effects of the pharmacological treatment would be more pronounced in coronary ligated trout compared to trout with intact coronaries. Coronary blockade reduced CTmax by 1.5 °C, constrained stroke volume and cardiac output across temperatures, led to earlier cardiac failure and was associated with reduced blood oxygen-carrying capacity. Nonetheless, CTmax and the temperatures for cardiac failure were not affected by autonomic blockade. Collectively, our data show that coronary perfusion improves heat tolerance and cardiac performance in trout, while evidence for beneficial effects of altered cardiac autonomic tone during warming remains inconclusive.

中文翻译：

---

热不起来？心脏控制和冠状动脉灌注对虹鳟耐热性的重要性

冠状动脉灌注和心脏自主调节可能有益于心肌氧输送和硬骨心脏的热性能，从而影响整个动物的耐热性。然而，没有研究检查冠状动脉灌注如何在体内变暖期间影响心输出量。此外，虽然 β-肾上腺素能刺激可以保护心脏收缩力，并且心率的胆碱能降低可能会在极端高温下增强心肌氧扩散，但先前在虹鳟鱼（Oncorhynchus mykiss）中使用药理学拮抗剂阻断胆碱能和 β-肾上腺素能调节的研究显示出矛盾心功能和耐热性的结果。这可能反映了冠状动脉灌注改变缓冲药物阻断的潜在负面影响程度的特异性差异。在这里，我们首先测试了冠状动脉结扎后心脏性能和临界热最大值 (CTmax) 是如何受到影响的。然后，我们评估了这些表现如何受到药理学胆碱能或 β-肾上腺素能阻断剂的影响，假设与具有完整冠状动脉的鳟鱼相比，冠状动脉结扎鳟​​鱼的药物治疗效果更显着。冠状动脉阻断使 CTmax 降低 1.5 °C，限制每搏输出量和不同温度的心输出量，导致早期心力衰竭，并与血氧携带能力降低有关。尽管如此，CTmax 和心力衰竭的温度不受自主神经阻滞的影响。总的来说，我们的数据表明冠状动脉灌注提高了鳟鱼的耐热性和心脏性能，