An Observation on Action Potentials of the Small Bronchioles in a Cat

Abstract

Action potentials were recorded from the smooth muscles of the small bronchioles (under 1 mm in diameter) with needle electrodes and glass capillary microelectrodes in a nembutalized cat. The results obtained were as follows.1) A local application of a drop of diluted acetylcholine solution produced an increase in the frequency of the spontaneous discharges and adrenaline administration resulted in a decrease or abolition of the spontaneous discharges.2) Spontaneous discharges from the bronchiole muscle and nerves were recorded in a denervated and immobilized lung.3) Waxing and waning of the spontaneous spike discharges was observed by continuous electrical stimulation of the cut vagus nerve.4) Intracellularer recording revealed that an evoked action potential of a bronchiole muscle fiber was preceded by a slow potential composed of small electric wavelets.5) Some aspects of a mode of activity of a single muscle fiber in the small bronchioles were discussed.