Peripheral vascular responses during stimulation of the low pressure receptors in man.

Several studies have been devoted to the cardiovascular responses to stimulation of low pressure receptors in animals. Yet, in man, the vascular participation in this reflex response is not fully documented. In the present work, the response of forearm and finger blood vessels was studied in a group of healthy subjects during stimulation of the low pressure receptors, using lower body negative pressure (LBNP) at -10, -20 and -40 mmHg. Blood flow was measured simultaneously at the forearm and the finger with an electrocardiogram (ECG)-triggered venous occlusion plethysmograph. Blood pressure remained unchanged at LBNP -10 and -20 mmHg, while there was a significant decrease of systolic and mean arterial blood pressure at LBNP -40 mmHg. Heart rate significantly increased at LBNP -20 and -40 mmHg, while no change in heart rate was seen at LBNP -10 mmHg. There was a significant decrease of blood flow at the forearm and a significant increase of the vascular resistance at LBNP -10, -20 and -40 mmHg. There were no changes in finger circulation. Thus, peripheral circulation is only partially involved in the cardiovascular response to stimulation of the low pressure receptors in men. There is a significant vasoconstriction of forearm blood vessels, occurring before any change in blood pressure and heart rate, while finger blood vessels do not participate in this reflex.