Respiratory neuronal activities in spinal afferents of cat.

The integrative function of the bulbar reticular formation for respiratory movements has long been established by experiments of denervation, ablation or gross stimulation. Many works are in agreement with the view of the pneumotaxic mechanism of the upper pons and the vagal lung afferents, both influencing the bulbar respiratory rhythm8,9,10,12,13). Spontaneous neuronal discharges, synchronous with respiratory movements, were first recorded by GESELL, BRICKER and MAGEE5) in the dog madulla. They described that the bulbar reticular gray matter was influenced by all the types of sensory signal, but most profoundly by those coming through the fifth, ninth, tenth, eleventh and twelfth cranial nerves and the sensory roots of the spinal cord. Using microelectrode techniques, YAMAMOTO and his coworkers14,15) could record impulse discharges occurring synchronously with respiratory movements in the dorsal funiculus and in the spinocerebellar tract of the cat. These impulse discharges are proprioceptive in nature in the sense that adaptation is very slow, and considered to originate in the chest wall. The present work was carried out to explore the spinal cord of the cat with a microelectrode for the purpose of determining the nature and distribution of respiratory afferent neurons.