THE INFLUENCE OF LEFT VENTRICULAR PRESSURE ON THE VASCULAR RESPONSES TO CHANGES IN CAROTID SINUS PRESSURE IN ANAESTHETIZED DOGS

¹ Department of Cardiovascular Studies, University of Leeds, Leeds LS2 9JT

The aim of this study was to determine whether the degree of stimulation of left ventricular receptors influenced the sensitivity of the carotid sinus baroreceptor reflex. In anaesthetized dogs, the stimulus to left ventricular receptors was changed by changing aortic root and hence ventricular systolic pressure, using a preparation in which the applied pressure did not distend the aortic arch and in which left atrial pressure was controlled. A large step increase in either carotid or left ventricular pressure resulted in vasodilatation both in a perfused hindlimb and in the remainder of the systemic circulation and resulted in a reduction in the response to a change in pressure in the other area. The stimulus-response curves, relating limb and systemic perfusion pressures to small step changes in carotid sinus pressure, were displaced downwards at high left ventricular pressures. However, the curves remained parallel indicating the absence of an interactive effect. These results indicate that the vascular responses to changes in carotid and ventricular pressures show simple additive summation.