Supraspinal and spinal control mechanisms in respiration.

In anaesthetized, paralyzed, ventilated and vagotomized cats, stimulation of somatic afferent nerves at fixed times in the respiratory cycle could delay or advance the onset of the next respiratory phase. Repetitive stimulation produced sustained increases in respiratory frequency, entrainment of the frequency of the respiratory oscillator to that of stimulation occurring in half of the cats. These observations demonstrate the existence of a reflex pathway which may account for the locking of respiratory frequency to the period of rhythmic muscular activity. In anaesthetized, non-vasotomized spontaneously breathing T1 spinal cats, the mouth pressure at which phrenic motoneurones were recruited was measured during airway occlusion. The threshold pressure of recruitment of a motoneurone was constant at a given end tidal CO2. No unit was recruited at a pressure greater than 70% of maximum. [...]Chez le chat anesthésié, vagotomisé, curarisé et ventilé par respirateur, la stimulation de nerfs somatiques afferents peut retarder ou avancer le debut de la prochaine phase respiratoire. Un stimulus répétitif augmente la fréquence respiratoire; chez la moitié des chats étudiés, il y'eut synchronisation entre la fréquence respiratoire et celle du stimulus. Ces observations démontrent l'existence d'une voie réflexe responsable de la synchronisation entre la fréquence respiratoire et celle de l'activité motrice. [...