Electrophysiological properties of the smooth muscle cell membrane of the dog coronary artery.

Abstract

The electrical properties of dog coronary arterial smooth muscles were studied with the partitioned chamber method and Wheatstone Bridge method. Effects of intracellular and extracellular current and of field stimulation of nerve were examined. Muscle from the anterior descending coronary artery showed cable properties with a 2.4 mm space constant and a 455 ms time constant. Muscle strips from the circumflex coronary artery showed poor cell-to-cell connections. The smooth muscle of both coronary arteries was electrically quiescent and action potentials were not evoked by strong outward current. Field stimulation of the descending coronary artery induced contraction or relaxation which were respectively associated with depolarization and hyperpolarization. The responses were blocked by tetrodotoxin (2 .times. 10-7 g/ml). Field stimulation produced depolarization when the membrane potential was < -50 mV. In the descending coronary artery, the smooth muscle including the innermost cells apparently can be controlled by nerves.