Responses of abdominal vascular capacitance to stimulation of splachnic nerves

In chloralose-anesthetized dogs the abdominal circulation was vascularly isolated without opening the abdominal cavity. The region was perfused at constant flow through the aorta and drained at constant pressure from the inferior vena cava. Changes in resistance were calculated from changes in perfusion pressure and changes in capacitance were calculated by integrating changes in venous outflow. Stimulation of both splanchnic nerves at 20 Hz increased resistance by 135% and reduced capacitance by 7.20 ml kg-1. The capacitance responses at 1 and 2 Hz (3.42 and 5.43 ml kg-1) were 48 and 67% of the responses at 20 Hz, However, the resistance responses at 1 and 2 Hz (14 and 31% increase) were only 12 and 26% of the responses at 20 Hz. After occlusion of the splenic pedicle, capacitance responses were reduced by about 40%. Although changes in inferior vena caval pressure changed the volume of blood in the abdomen by 0.92 ml kg-1 cmH2O-1, the responses to stimulation were relatively constant in any one animal at constant venous pressures between 5 and 15 cmH2O.