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Ventilatory responses of the clown knifefish, Chitala ornata, to arterial hypercapnia remain after gill denervation
Journal of Comparative Physiology B ( IF 1.7 ) Pub Date : 2019-09-24 , DOI: 10.1007/s00360-019-01236-6
Dang Diem Tuong 1 , Do Thi Thanh Huong 1 , Nguyen Thanh Phuong 2 , Mark Bayley 3 , William K Milsom 4
Affiliation  

The aim of this study was to corroborate the presence of CO2/H+-sensitive arterial chemoreceptors involved in producing air-breathing responses to aquatic hypercarbia in the facultative air-breathing clown knifefish (Chitala ornata) and to explore their possible location. Progressively increasing levels of CO2 mixed with air were injected into the air-breathing organ (ABO) of one group of intact fish to elevate internal PCO2 and decrease blood pH. Another group of fish in which the gills were totally denervated was exposed to aquatic hypercarbia (pH ~ 6) or arterial hypercapnia in aquatic normocarbia (by injection of acetazolamide to increase arterial PCO2 and decrease blood pH). Air-breathing frequency, gill ventilation frequency, heart rate and arterial PCO2 and pH were recorded during all treatments. The CO2 injections into the ABO induced progressive increases in air-breathing frequency, but did not alter gill ventilation or heart rate. Exposure to both hypercarbia and acetazolamide post-denervation of the gills also produced significant air-breathing responses, but no changes in gill ventilation. While all treatments produced increases in arterial PCO2 and decreases in blood pH, the modest changes in arterial PCO2/pH in the acetazolamide treatment produced the greatest increases in air-breathing frequency. These results strengthen the evidence that internal CO2/H+ sensing is involved in the stimulation of air breathing in clown knifefish and suggest that it involves extra-branchial chemoreceptors possibly situated either centrally or in the air-breathing organ.

中文翻译:

小丑刀鱼 Chitala ornata 对动脉高碳酸血症的通气反应在去鳃后仍然存在

本研究的目的是证实 CO2/H+ 敏感动脉化学感受器的存在,这些化学感受器参与对兼性呼吸空气的小丑刀鱼 (Chitala ornata) 的水生高碳酸血症产生呼吸空气反应,并探索它们的可能位置。逐渐增加水平的二氧化碳与空气混合被注入一组完整鱼的呼吸器官(ABO),以提高内部 PCO2 并降低血液 pH 值。另一组鳃完全去神经支配的鱼暴露于水生高碳酸血症(pH ~ 6)或水生正常碳酸血症中的动脉高碳酸血症(通过注射乙酰唑胺增加动脉 PCO2 并降低血液 pH 值)。在所有处理过程中记录空气呼吸频率、鳃通气频率、心率和动脉 PCO2 和 pH 值。注入 ABO 的 CO2 导致呼吸频率逐渐增加,但不会改变鳃通气或心率。鳃去神经后暴露于高碳酸血症和乙酰唑胺也产生显着的空气呼吸反应,但鳃通气没有变化。虽然所有治疗都会导致动脉 PCO2 增加和血液 pH 值降低,但乙酰唑胺治疗中动脉 PCO2/pH 的适度变化导致呼吸频率的最大增加。这些结果加强了内部 CO2/H+ 感应参与刺激小丑刀鱼呼吸空气的证据,并表明它涉及可能位于中央或呼吸空气器官中的分支外化学感受器。但没有改变鳃通气或心率。鳃去神经后暴露于高碳酸血症和乙酰唑胺也产生显着的空气呼吸反应,但鳃通气没有变化。虽然所有治疗都会导致动脉 PCO2 增加和血液 pH 值降低,但乙酰唑胺治疗中动脉 PCO2/pH 的适度变化导致呼吸频率的最大增加。这些结果加强了内部 CO2/H+ 感应参与刺激小丑刀鱼呼吸空气的证据,并表明它涉及可能位于中央或呼吸空气器官中的分支外化学感受器。但没有改变鳃通气或心率。鳃去神经后暴露于高碳酸血症和乙酰唑胺也产生显着的空气呼吸反应,但鳃通气没有变化。虽然所有治疗都会导致动脉 PCO2 增加和血液 pH 值降低,但乙酰唑胺治疗中动脉 PCO2/pH 的适度变化导致呼吸频率的最大增加。这些结果加强了内部 CO2/H+ 感应参与刺激小丑刀鱼呼吸空气的证据,并表明它涉及可能位于中央或呼吸空气器官中的分支外化学感受器。但鳃通气没有变化。虽然所有治疗都会导致动脉 PCO2 增加和血液 pH 值降低,但乙酰唑胺治疗中动脉 PCO2/pH 的适度变化导致呼吸频率的最大增加。这些结果加强了内部 CO2/H+ 感应参与刺激小丑刀鱼呼吸空气的证据,并表明它涉及可能位于中央或呼吸空气器官中的分支外化学感受器。但鳃通气没有变化。虽然所有治疗都会增加动脉 PCO2 并降低血液 pH 值,但乙酰唑胺治疗中动脉 PCO2/pH 值的适度变化导致呼吸频率的最大增加。这些结果加强了内部 CO2/H+ 感应参与刺激小丑刀鱼呼吸空气的证据,并表明它涉及可能位于中央或呼吸空气器官中的分支外化学感受器。
更新日期:2019-09-24
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