Ekström Andreas, Gräns Albin, Sandblom Erik
Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30, Göteborg, Sweden.
Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Göteborg, Sweden.
J Comp Physiol B. 2019 Nov 9. doi: 10.1007/s00360-019-01243-7.
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 (CT) 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 CT 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, CT 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.
冠状动脉灌注和心脏自主神经调节可能有益于硬骨鱼心脏的心肌氧输送和热性能，从而影响动物整体的耐热性。然而，尚无研究考察在体内升温过程中冠状动脉灌注如何影响心输出量。此外，虽然β-肾上腺素能刺激可保护心脏收缩力，且在极高温度下胆碱能使心率降低可能会增强心肌氧扩散，但此前在虹鳟（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在心脏性能和耐热性方面得出了相互矛盾的结果。这可能反映了种内差异，即冠状动脉灌注改变缓冲药理学阻断潜在负面影响的程度不同。在此，我们首先测试冠状动脉结扎后心脏性能和临界热最大值（CT）如何受到影响。然后，我们评估药理学胆碱能或β-肾上腺素能阻断如何影响这些性能，假设与冠状动脉完整的鳟鱼相比，药理学处理对冠状动脉结扎的鳟鱼影响更显著。冠状动脉阻断使CT降低了1.5°C，限制了不同温度下的搏出量和心输出量，导致更早出现心力衰竭，并与血液携氧能力降低有关。尽管如此，CT和出现心力衰竭的温度不受自主神经阻断的影响。总体而言，我们的数据表明冠状动脉灌注可提高鳟鱼的耐热性和心脏性能，而升温过程中心脏自主神经张力改变产生有益影响的证据仍不明确。
