Respiratory and cardiovascular responses to temperature changes in the perfused pulmonary arteries of the dog.

In chloralose-anaesthetized dogs a right heart bypass was established and the isolated main pulmonary arteries were perfused at controlled pressure and temperature. Increasing pulmonary arterial pressure by 20-60 mmHg (1 mmHg = 133.322 Pa) increased systemic vascular resistance and respiratory activity. Decreasing the temperature of the pulmonary arterial perfusate over the range 37-31 degrees C decreased systemic arterial pressure and respiratory activity. Increasing the temperature over the range 37-41 degrees C had the opposite effects. The decreases in systemic arterial pressure and respiratory activity in response to a decrease in temperature of the pulmonary arterial perfusate were present at low (20 mmHg) or high (80 mmHg) pulmonary arterial pressures. All responses to changing the pressure or temperature of the pulmonary arterial perfusate were prevented by cutting the vagosympathetic nerves in the neck. It is concluded that there are receptors, lying in or close to the pulmonary arterial walls, that in this preparation are tonically active. Their discharge is affected by changes of +/- 2 degrees in pulmonary arterial temperature.