Abstract
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.