ABSTRACT
Cardiac output and peripheral resistance have not been measured in conscious anuran amphibians, although some data exist for pithed and anaesthetized frogs (Shelton and Jones, 1965a,b; Shelton, 1970; Tazawa et al. 1979). The periodic lung ventilation characteristic of conscious anurans could increase cardiac output reflexively or by changes in venous return, as in mammals. Furthermore, because the undivided ventricle places the pulmonary and systemic vascular beds effectively in parallel, changes in the ratio of systemic to pulmocutaneous vascular resistance have the potential to alter the distribution of cardiac output. Therefore, the objectives of this study were to measure cardiac output and peripheral resistance in undisturbed, conscious Bufo marinus and to determine the effect of increased ventilation, stimulated by CO2, on pulmocutaneous blood flow and resistance.
