Arterial pressure changes by drugs injected into isolated pulmonary circulation in dogs

Abstract

In open-chested, anesthetized dogs the pulmonary venous outflow of the left lung was diverted into an external bypass so that the flow rate could be measured and blood prevented from returning immediately to the general circulation. Pulmonary arterial pressure was recorded in the left pulmonary artery; systemic arterial pressure and heart rate were also recorded. Injection of nicotine, veratrine, or Veriloid into this limited lung circulation produced a systemic depressor response and bradycardia. Both effects were abolished by vagotomy. It is concluded that these systemic cardiovascular effects are mediated through vagal chemoreceptors. There is no reason to implicate a mechanical pulmonary depressor reflex since these drugs produce no change in the pulmonary arterial pressure.