Reid S G, Sundin L, Kalinin A L, Rantin F T, Milsom W K
Department of Zoology, University of British Columbia, Vancouver, Canada.
Respir Physiol. 2000 Mar;120(1):47-59. doi: 10.1016/s0034-5687(99)00100-0.
To examine the distribution and physiological role of CO2/pH-sensitive chemoreceptors in the gills of the tropical fish, traira (Hoplias malabaricus), fish were exposed to acute environmental hypercarbia (1.25, 2.5 and 5.0% CO2 in air) and subjected to injections of HCl into the ventral aorta and buccal cavity. This was done before and after selective denervation of branchial branches of the IXth and Xth cranial nerves to various gills arches. Hypercarbia produced a significant decrease in heart rate, a mild hypotension as well as increases in both ventilation rate and ventilation amplitude. The data suggest that the hypercarbic bradycardia and increase in ventilation frequency arise from receptors exclusively within the gills but present on more than the first gill arch, while extra-branchial receptors may also be involved in controlling the increase in ventilation amplitude. With the exception of a decrease in heart rate in response to HCl injected into the ventral aorta, the acid injections (internal and external) did not mimic the cardiorespiratory responses observed during hypercarbia suggesting that changes in CO2 are more important than changes in pH in producing cardiorespiratory responses. Finally, the data indicate that chemoreceptors sensitive to CO2/pH and to O2 in the gills of this species involved in producing ventilatory responses are distributed in a similar fashion, but that those involved in producing the bradycardia are not.
为研究热带鱼类——巴西狼鱼（Hoplias malabaricus）鳃中二氧化碳/酸碱度敏感化学感受器的分布及生理作用，将鱼暴露于急性环境高碳酸血症（空气中二氧化碳含量为1.25%、2.5%和5.0%）中，并向腹主动脉和口腔内注射盐酸。这一操作在选择性切断第九和第十对脑神经至各鳃弓的鳃分支之前和之后进行。高碳酸血症导致心率显著下降、轻度低血压以及通气率和通气幅度增加。数据表明，高碳酸血症引起的心动过缓和通气频率增加源于鳃内的感受器，但不止存在于第一鳃弓，而鳃外感受器可能也参与控制通气幅度的增加。除了向腹主动脉注射盐酸导致心率下降外，酸注射（内部和外部）并未模拟高碳酸血症期间观察到的心肺反应，这表明在产生心肺反应方面，二氧化碳的变化比酸碱度的变化更重要。最后，数据表明，该物种鳃中对二氧化碳/酸碱度和氧气敏感、参与产生通气反应的化学感受器分布方式相似，但参与产生心动过缓的化学感受器分布方式不同。
