The role of alpha and beta adrenergic receptors in constriction and dilation of the systemic capacitance vessels: A study with measurements of the mean circulatory pressure in dogs

The response of the mean circulatory pressure (MCP), an index of the tone of the systemic capacitance vessels, to the infusion of an alpha-adrenergic receptor stimulant (phenylephrine) and a beta-adrenergic receptor stimulant (isoproterenol) was studied in anesthetized, open-chest dogs. Provided that the blood volume (particularly, extra volume) remains constant, an increase in the MCP indicates an increase in the tone of the capacitance vessels (“venoconstriction”) and a decrease in the MCP indicates a decrease in the tone of the capacitance vessels (“venodilation”). It was almost definitely concluded that the stimulation of the alpha-adrenergic receptor led to the increased tone of the systemic capacitance vessels and the stimulation of the beta-adrenergic receptor did not decrease the tone of the systemic capacitance vessels in anesthetized, open-chest dogs, but the stimulation of the beta-adrenergic receptor decreased the tone of the systemic capacitance vessels, when the tone had been previously elevated by angiotensin-II.