The effect of carotid sinus pressure changes on mean circulatory filling pressure in the anaesthetized rabbit

The effect on mean circulatory filling pressure (MCFP) of changes in pressure within the vascularly isolated carotid sinus has been studied in anaesthetized rabbits. With the sinus exposed to arterial pressure (102 +/- 6 mm Hg; mean +/- SEM) MCFP was 6.18 +/- 0.40 mm Hg. At sinus pressures of 160 and 40 mm Hg, MCFP was 5.71 +/- 0.39 and 6.43 +/- 0.33 mm Hg respectively. The mean difference of 0.72 +/- 0.06 mm Hg between MCFP at these two sinus pressures was significant (P < 0.001). MCFP varied with blood volume when this was increased or reduced by 8%, but at each blood volume level the difference between MCFP at high and low sinus pressure remained significant (P < 0.01). The gradient for venous return, MCFP minus right atrial pressure, was altered by changes in carotid sinus pressure, being 0.60 +/- 0.12 mm Hg less at a sinus pressure of 160 mm Hg than at a sinus pressure of 40 mm Hg. This difference was significant (P < 0.01).