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Journal of Experimental Biology 57,789-803 (1972)
Published by Company of Biologists 1972

Factors Affecting Diastolic Blood Pressures in the Systemic and Pulmocutaneous Arches of Anuran Amphibia

DAVID R. JONES ¹ and GRAHAM SHELTON ²

¹ Department of Zoology, University of British Columbia Vancouver 8, B.C.
² School of Biological Sciences, University of East Anglia Norwich, NOR 88C, U.K.

1. During rhythmic lung ventilation systolic blood pressures in the pulmocutaneous and systemic arches were more or less the same although diastolic pressures in the former were some 3-4 cm H₂O lower than in the latter. During prolonged apnoea (20-35 min) the pulse pressures became identical. Venous pressures in both lung and body circuits were little affected by these procedures.

2. Raising or reducing systolic pressure by application of drugs to the exposed ventricle caused no change in the relationships of the pressure pulses in the systemic and pulmocutaneous arches.

3. Removal of the conus arteriosus and spiral valve caused a significant reduction in diastolic pressure in the systemic but not in the pulmocutaneous arch.

4. After conus removal differences in diastolic pressures in the systemic and pulmocutaneous arches were only recorded when valves at the apex of the conus were functional.

5. Bilateral occlusion of both systemic arches produced a greater increase in systolic blood pressure in the systemic and pulmocutaneous arches than bilateral occlusion of the pulmocutaneous arches, although pressure changes following the latter were more variable.

6. Blood flow in the pulmocutaneous arch was extremely variable, lowest stroke flows being recorded when the pressure pulses in the systemic and pulmocutaneous arches were identical.

7. The role of the conus arteriosus, spiral valve, arterial compliance and peripheral resistance in maintenance of diastolic pressures in the systemic and pulmocutaneous arches is discussed.