Hemodynamic significance of the carotid rete during changes in arterial blood pressure.

We attempted to characterize in the goat the hemodynamic response of the carotid rete during large, passive changes in blood pressure in the afferent limb of the rete produced by mechanical constriction of the thoracic aorta or the inferior vena cava. Experiments in 12 anesthetized goats demonstrated that calculated resistance through the rete decreases in hypertension and increases in hypotension, whereas changes in resistance through brain vessels follow opposite directions. The consequence of this is that the carotid rete, by passively decreasing its resistance to blood flow in hypertension, acts as a flow-facilitating system in a situation in which smooth muscle of brain vessels contracts in response to stretch. Contrariwise, by increasing its resistance to blood flow during systemic hypotension, the carotid rete "limits" the passage of blood when active relaxation of brain vessels takes place.