Zoology Department, University of British Columbia, Vancouver, British Columbia, Canada.
Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada.
J Fish Biol. 2019 Nov;95(5):1265-1274. doi: 10.1111/jfb.14126. Epub 2019 Oct 21.
Here, we show that heart rate in zebrafish Danio rerio is dependent upon two pacemaking mechanisms and it possesses a limited ability to reset the cardiac pacemaker with temperature acclimation. Electrocardiogram recordings, taken from individual, anaesthetised zebrafish that had been acclimated to 18, 23 or 28°C were used to follow the response of maximum heart rate (f ) to acute warming from 18°C until signs of cardiac failure appeared (up to c. 40°C). Because f was similar across the acclimation groups at almost all equivalent test temperatures, warm acclimation was limited to one significant effect, the 23°C acclimated zebrafish had a significantly higher (21%) peak f and reached a higher (3°C) test temperature than the 18°C acclimated zebrafish. Using zatebradine to block the membrane hyperpolarisation-activated cyclic nucleotide-gated channels (HCN) and examine the contribution of the membrane clock mechanisms to cardiac pacemaking, f was significantly reduced (by at least 40%) at all acute test temperatures and significantly more so at most test temperatures for zebrafish acclimated to 28°C vs. 23°C. Thus, HCN channels and the membrane clock were not only important, but could be modified by thermal acclimation. Using a combination of ryanodine (to block sarcoplasmic calcium release) and thapsigargin (to block sarcoplasmic calcium reuptake) to examine the contribution of sarcoplasmic reticular handling of calcium and the calcium clock, f was again consistently reduced independent of the test temperature and acclimation temperature, but to a significantly lesser degree than zatebradine for zebrafish acclimated to both 28 and 18°C. Thus, the calcium clock mechanism plays an additional role in setting pacemaker activity that was independent of temperature. In conclusion, the zebrafish cardiac pacemaker has a limited temperature acclimation ability compared with known effects for other fishes and involves two pacemaking mechanisms, one of which was independent of temperature.
在这里，我们表明斑马鱼的心率取决于两种起搏机制，并且它具有通过温度适应重置心脏起搏器的有限能力。从已经适应 18°C、23°C 或 28°C 的个体麻醉斑马鱼中记录心电图，以跟踪最大心率 (f) 对从 18°C 急性升温的反应，直到出现心力衰竭迹象（高达约 40°C）。由于在几乎所有等效测试温度下，f 在适应组之间相似，因此温暖适应仅限于一个显著的效果，23°C 适应的斑马鱼具有显著更高的（21%）峰值 f，并且达到更高的（3°C）测试温度比 18°C 适应的斑马鱼。使用扎特布雷丁阻断膜超极化激活环核苷酸门控通道 (HCN) 并检查膜时钟机制对心脏起搏的贡献，在所有急性测试温度下，f 都显著降低（至少降低 40%），对于适应 28°C 的斑马鱼，在大多数测试温度下，f 降低更为显著，而对于适应 23°C 的斑马鱼。因此，HCN 通道和膜时钟不仅重要，而且可以通过热适应进行修饰。使用组合的ryanodine（阻断肌浆网钙释放）和 thapsigargin（阻断肌浆网钙摄取）检查肌浆网处理钙和钙时钟的贡献，f 再次独立于测试温度和适应温度而一致降低，但对于适应 28 和 18°C 的斑马鱼，其降低程度明显低于扎特布雷丁。因此，钙时钟机制在设定起搏活动方面具有额外的作用，而与温度无关。总之，与其他鱼类的已知作用相比，斑马鱼心脏起搏器的温度适应能力有限，涉及两种起搏机制，其中一种与温度无关。
