Changes in Peripheral Blood Flow Distribution in Healthy Dogs

Abstract

The instantaneous velocity and the integrated flow through a splanchnic artery (superior mesenteric or hepatogastric), the renal artery, and the terminal abdominal aorta were recorded continuously and simultaneously, as were the mean aortic pressure and heart rate, during a wide variety of spontaneous cardiovascular adjustments of healthy active dogs. These responses were compared with the effects of infusing vasoactive substances, such as isoproterenol, l-epinephrine, norepinephrine, acetyichol lie, and Pitressiii, and with P to stimulation of selected sites in the base of the brain. During sponta neous activity, the flow through the splanch nic and renal arteries usually varied in a direction opposite to that of changes in flow to the hindciuarters. The changes in mesen teric or renal flow were relatively slight, even during strenuous exercise that produced a substantial increase in flow to the hindciuar ters. Vasoactive substances tended to produce changes in the same direction in all three beds. Changes in flow distribution and in wave forms of the instantaneous flow patterns produced by vasoactive substances did not resemble those produced by spontaneous ad justment. 1-lowever, stimulation of selected diencephalic sites (e.g., 112 fields of Forel) produced changes in both flow distribution and flow velocity patteras that closely simu lated those observed during exercise in the same animals. Stimulation in the same re gions was previously reported to produce changes in left ventricular performance also closely resembling those noted during tread mill exercise.