Hepatic vein, hepatic parenchymal, and inferior vena caval mechanoreceptors with phrenic afferents.

Dogs were anesthetized with pentobarbital sodium and placed on positive-pressure ventilation. The right phrenic nerve and/or its C5 branch were prepared for afferent recording. The hepatic veins, hepatic parenchyma, diaphragm, and inferior vena cava were studied for mechanoreceptors using light pressure and stroking as the stimuli. Mechanosensitive areas were found in the hepatic veins, hepatic parenchyma of the right medial lobe, and inferior vena cava. The hepatic vein and inferior vena caval receptors are located in the same 1- to 2-cm region as the sphincters that are found in these vessels. This study presents the first experimental evidence for the existence of hepatic vein receptors, hepatic parenchymal receptors, and inferior vena caval mechanoreceptors with phrenic afferents in the dog. These sensory areas of the circulation may be involved in the neural control of venous return as well as mediating changes in intrahepatic and portal venous blood pressure during normal respiration.