Electrical Quiescence of Pulmonary Artery Smooth Muscle During Sympathomimetic Stimulation

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Abstract
Simultaneous recordings of isometric tension and muscle membrane potential have been made in the sympathetic nerve-pulmonary artery preparation of the rabbit. The mean resting membrane potential recorded intracellularly was 51.5 mv. Sympathetic nerve stimulation and l-norepinephrine caused contraction without change in the membrane potential and in the absence of action potentials. Increase in extracellular potassium initiated both depolarization and contraction, although these two processes exhibited different latencies and time courses. The significance of these findings is discussed in relation to recent findings of dissociation in smooth muscle between contraction and membrane potential changes.