Effect of stimulating right atrial receptors on renal blood flow

This investigation was undertaken to determine the effect of stretching the superior vena caval--right atrial (SVC-RA) junction and the right atrial appendage on blood flow to the kidney (RBF) and to establish whether any changes observed were influenced by the input from the baroreceptors in the carotid sinus. The experiments were performed on seven dogs, anaesthetized with alpha-chloralose. The systemic arterial (i.e., renal perfusion) pressure was held constant. At a carotid sinus pressure (CSP) of 59.0 +/- 1.2 mmHg (1 mmHg = 133.322 Pa), the RBF increased from 218 +/- 16.1 to 231.7 +/- 18.4 mL/min per 100 g renal mass (p less than 0.025). At a CSP of 88.0 +/- 3.5 mmHg, the RBF increased from 230.1 +/- 19.2 to 237.1 +/- 19.2 mL/min per 100 g renal mass (p less than 0.05). At a CSP of 137 +/- 3.7 mmHg there were no significant changes in RBF. These responses were abolished by cutting (four dogs) or cooling the vagi (one dog only). In a subsidiary investigation it was shown that stretching the SVC-RA junction activated receptors in the endocardial surface of the right atrium which discharged into myelinated fibres in the vagi, having an average conduction velocity of 8.1 m/s (range 3.8-15). It is concluded that stimulation of right atrial receptors increases the RBF and that this response is influenced by the input from the baroreceptors in the carotid sinus.