PHASIC CONTRACTIONS OF THE MUSCULAR COMPONENTS OF HUMAN ESOPHAGUS AND GASTROESOPHAGEAL JUNCTION IN-VITRO

This study was performed to assess the repetitive phasic mechanical and (or) electrical activity of the muscle from different regions of the human gastroesophageal junction (GEJ). Muscle strips from the circular and longitudinal layers of the gastric fundus and esophagus and of the clasp and sling components of the GEJ were obtained from surgical specimens and prepared for in vitro recording of contractile or electrical activity. Phasic contractions occurred in all regions except the longitudinal muscle of the gastric fundus and that overlying the sling. Robust phasic activity (2.6 +/- 0.6 min(-1)) was most frequent (92% of specimens) in longitudinal muscle overlying the clasp, arising spontaneously in 67%. Stretch or carbachol stimulation increased the frequency of these contractions. Transmural electrical stimulation produced a transient cessation of phasic activity. Electrical recording showed slow waves with superimposed spiking coinciding with phasic contractions. These activities were unaltered by 1 mu M atropine or 1 mu M tetrodotoxin, but inhibited by 2 mu M verapamil. In conclusion, several muscles of the human esophagus and GEJ manifest repetitive contractions in vitro, particularly the longitudinal muscle overlying the clasp muscle fibers. These oscillations are due to electrical slow waves, can potentially be modulated by intrinsic nerves, and may play a role in the intermittent phasic contractions of lower esophageal sphincter pressure in vivo.