The Frequency-Dependent Nature of Blood Pressure Regulation by the Carotid Sinus Studied with an Electric Analog

Amplification of carotid sinus activity of a dog is brought about through the use of an elec-tric analog of the carotid sinus applied in parallel with this element of the dog's own pres-sure regulating system. Sinusoidal excursions in arterial pressure in response to corresponding variations, between fixed limits, in rate of stimulus of one vagus nerve were larger with carotid sinus amplification than without it. Evidence presented supports the concept that because of the delay in the response of arteriolar smooth muscle, effective buffering of sudden varia-tions in arterial pressure cannot be accomplished by variations in resistance, but can be through variations in flow. THE carotid sinus constitutes but one partof a clog's blood pressure control system. To date, studies which have aimed at defining the role played by the carotid sinus as an in-tegral part of this regulating system have been limited to observations on the effects of removal of one or both carotid sinuses or the effects of surgical or phannacologic interrup-tion of nervous pathways in other parts of the blood pressure regulating system. As yet data regarding the effect on the integrated regulation of arterial pressure of varying quantitatively the characteristics of the ca-rotid sinus function are not available. In the present study an electric analog of the carotid sinus, whose parameters could be readily va-ried, has been employed in an attempt to ob-tain such data. The use of this device has made possible amplification of the effects of carotid sinus activity, thus emphasizing both the advantages and the limitations of this or-gan as an element of the blood-pressvire regu-lating system. Dlfftr tntiato