[Effect of spinal cord section on extravagal diaphragmatic reflexes].

In anesthetized vagotomized cats breathing under resting conditions, responses of the phrenic motoneurons to tracheal occlusion, and to changes of the lung and chest volumes were studied before and after cordotomy between C6 and T1. The cordotomy did not change the breathing rate whereas the inspiratory period shortened and expiratory one became longer. The cordotomy eliminated the slight shortening of inspiration in response to tracheal occlusion. The slight decrease of inspiratory excitation of phrenic motoneurons and prolongation of the expiration in response to tracheal occlusion remained. After the cordotomy the increase and decrease of chest volumes were not accompanied by any consistent changes in activity of the phrenic motoneurons.