Effects of sinus nerve stimulation on activity of phrenic motoneurones [18]

IT is well known that stimulation of arterial pressure receptors causes a depression of respiration¹. Little is known, however, about the site of this depression, that is, whether it is effected on interneurones in the brain stem, on phrenic motoneurones, or on both. A clue to this problem was provided during an investigation of the central connexions of the carotid sinus nerve in the cat. In these experiments we have observed that a single maximal electrical stimulus to the sinus nerve can inhibit spontaneous activity in the phrenic nerve. Some of the properties of this depression of phrenic nerve activity are described here.