[Respiratory regulations of pulmonary vagal nerves under hypercapnic conditions; effects of J-receptor].

We studied ventilatory responses under hypercapnic condition in 9 lightly anesthetized dogs, using a vagal nerve cooling technique. One side of the cervical vagosympathetic trunks of dogs were previously severed, and a copper cooler was attached to the other side. When the cervical nerve was cooled below 7 degrees C, the Hering-Breuer inflation reflex ceased. We found that when the vagal nerve was not cooled or cooled to 7 degrees C, the respiratory frequency increased significantly in relation to hypercapnic gas inhalation. However, the increment of respiratory frequency was reduced by bilateral cervical vagotomy. We concluded that the J-receptor is responsible for the increase in respiratory frequency under hypercapnic gas inhalation.