Electrical and mechanical activity in the lower esophageal sphincter of the cat

Transmembrane electrical activity was correlated to isometric contractile activity for strips of circularly oriented smooth muscle from the feline lower esophageal sphincter (LES). Strips first were identified mechanically as being from the LES, and then either their cellular electrical activities were monitored with microelectrodes or their mechanical activities were monitored with force-displacement transducers. The mean resting membrane potential was -40.6 +/- 1.1 (SE) mV. Transmural electrical stimulation (0.2-8 Hz) induced only hyperpolarizations that were graded and increased as the frequency of stimulation increased. Mechanically, all strips developed tone spontaneously. Electrical stimulation induced only relaxations that likewise were graded and varied directly with the frequency of stimulation. When compared quantitatively, there was a correlation between the integral of the hyperpolarization and the integral of the relaxation. Thus, the tension exerted by LES smooth muscle appears to be related to the amount of current crossing the membrane of the smooth muscle cells.