SENSORY RECEPTORS IN THE PULMONARY VASCULAR BED

Abstract

Methods are described for perfusing (in the dog):— (1) A head‐thorax‐preparation in which the systemic and pulmonary circulations are supplied by separate pumps, the systemic blood being oxygenated by isolated perfused lungs from another animal; (2) the entire animal by two separate pumps, the outlet connexions of which are tied into the pulmonary artery and ascending aorta; (3) the entire animal, less the lower limbs, by two separate pumps the outlet of one of which is tied into the abdominal aorta and the outlet of the other inserted into the right ventricle. In all three preparations an increase of pulmonary blood flow gives rise to a slight but definite fall in systemic arterial pressure and a rise or fall in heart rate. These effects do not appear after section of both cervical vagosympathetic nerves. An increase of pulmonary flow causes an acceleration of respiration in some preparations. Obstruction to the outflow of blood from the left auricle is more effective than a rise in pulmonary arterial pressure in producing cardiosystemic reflexes. The possible significance of these results in relation to the evocation of reflexes in consequence of left heart failure and of pulmonary embolism is discussed. The pulmonary arterial pressure may exhibit periodic variations unaccompanied by similar changes in the systemic arterial pressure. We wish to express our thanks to Dr. J. L. Berry and Miss Barbara Petrovskaia for help with some of the experiments, and to the Government Grants Committee of the Royal Society for defraying the expenses of the investigation by a grant to one of us (I. de B. D.).