Participation of the cardiopulmonary baroreceptors in the buffering of fast changes in the arterial pressure.

Acute experiments on cats are carried out to study the effect on the value of the pressor and depressor responses of the systemic arterial pressure (SAP) of the rise in the central venous pressure (CVP), occurring upon the administration of some hyper- and hypotensive agents. The responses of SAP to intravenous injection of different doses of noradrenaline and acetylcholine are determined at rest, after vagotomy, during intravenous infusion of dextrane solution and after vagotomy during infusion. It is shown that when the hypertensive agent causes a rise in CVP in addition to its pressor effect, the pressor response is subjected both to carotid and to aortic buffering as a result of the increased SAP, as well as to cardiopulmonary buffering due to the rise in CVP. In the case of the hypotensive agent the rise in CVP does not influence the value of the depressor SAP response, since the changes in the activation of the cardiopulmonary and arterial baroreceptors are in different directions. Evidence is presented in support of the assumption that the cardiopulmonary inhibition is transmitted along extravagal afferent ways in addition to being transmitted along the vagal nerves.