Phasic activity in the airways smooth muscle.
In anesthetized cats and rats additional observations were made on the oscillations that are usually seen in breathing pressure or flow records. It was confirmed that these oscillations have the same properties as those phasic responses to vagal stimulation since they interfere with each other. It was also confirmed that this type of activity represents a different phenomenon from the known tone changes, and that it depends from sympathetic control of the airways smooth muscle. The possible determinant role of the mechanical factors as stimuli was examined by applying positive or negative pressure pulses at the free end of the tracheal cannula and by the study of some other conditions in which there is a sudden lung distension. At this respect, pressure, volume and rate of air flow in the airways seemed to be all important as stimuli. The initial state of tension of the bronchial walls is also important. The obtained results suggest that mechanical stimulation is normally effective against a background of facilitatory influence from the sympathetic system.
García Ramos
J
J
Laboratorio de Neurofisiología, Facultad de Medicina, Universidad Autónoma de Querétaro, México.
D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D008168:Lung / Q000502:physiology; D008365:Manometry; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D051381:Rats; D012121:Respiration, Artificial