Effect of pulmonary lymphatic obstruction on respiratory rate and airway rapidly adapting receptor activity in rabbits.

1. The effects on respiratory rate of obstruction of pulmonary lymph flow, reduction of plasma protein concentration and a combination of the two procedures were examined in anaesthetized rabbits. The former was achieved by raising the pressure in a pouch created from the right external jugular vein and the latter by batch plasmapheresis. 2. In spontaneously breathing rabbits, neither pulmonary lymphatic obstruction (n = 6) nor plasmapheresis (n = 5) produced a significant change in respiratory rate. However, their combination (n = 8) produced a significant increase in respiratory rate (P < 0.05). 3. Cooling of the cervical vagi to 8-9 degrees C (n = 4) and vagotomy (n = 7) abolished this response. 4. There was a significant increase in the activity of the airway rapidly adapting receptors (RARs; n = 9) during pulmonary lymphatic obstruction, plasmapheresis and their combination (P < 0.05). 5. It is concluded that in the rabbit, obstruction of lymphatic drainage from the lung after plasmapheresis causes a reflex increase in respiratory rate. The afferent pathway for this reflex response lies in the vagus nerve and the RARs are likely to be the receptors involved in this response.