Abstract
1.Effects of stimulation of the central cut end of the phrenic nerve on the movements of the stomach and small intestine were investigated in dogs anesthetized with pentobarbital sodium and in the decerebrated or spinal dogs. The movements of the stomach and small intestine were recorded by means of the balloon method. The right phrenic nerve was electrically stimulated at the neck or just above the diaphragm under artificial respiration.
2. The stimulation of the phrenic nerve produced an augmentation of the gastrointestinal movements. The excitatory effects still persisted even after severing the bilateral vagus nerves, and after the severance of the bilateral thoracic splanchnic nerves, the excitatory effects were completely abolished. In one case, the severance of the bilateral thoracic splanchnic nerves did not much change the excitatory effect, but on cutting the bilateral cervical vagus nerves they were completely abolished.
3. In dogs decerebrated at the level of the midcolliculus, the excitatory effects similar to those observed in (2) were also obtained. These effects were abolished when the spinal cord was transected at the level of C3 following the severance of bilateral cervical vagi.
4. It may be concluded that the excitation of the gastrointestinal movements produced by stimulation of the phrenic nerve is elicited via the vagus as well as the thoracic spalanchnic nerves, and that one of the reflex centers is the vagus nuclei in the medulla oblongata and another is an unknown excitatory center located between the inferior colliculus and medulla oblongata.
