Esophageal distension causes simultaneous relaxation of the lower esophageal sphincter (LES) and crural diaphragm (CD). The mechanism of CD relaxation during esophageal distension is not well understood. AIMS: We studied the motion of crural and costal diaphragm along with the motion of the distal esophagus during esophageal distension induced relaxation of the LES and CD. METHODS: Wire electrodes were surgically implanted into the crural and costal diaphragm in 5 cats. In two additional cats, radio-opaque markers were also sutured into the outer wall of the distal esophagus to monitor esophageal shortening. Under light anesthesia, animals were placed on an X ray fluoroscope to monitor the motion of the diaphragm and the distal esophagus by tracking the radio-opaque markers. Crural and costal diaphragm EMGs were recorded along with the esophageal, LES and gastric pressures. A 2 cm balloon placed 5 cm above the LES was used for esophageal distension. Effects of baclofen, a GABA b agonist were also studied. RESULTS: Esophageal distension induced LES relaxation and selective inhibition of the crural diaphragm EMG. The crural diaphragm moved in a cranio-caudal direction with expiration and inspiration respectively. Esophageal distension induced inhibition of the crural EMG was associated with sustained cranial motion of the CD and esophagus. Baclofen blocked distension induced LES relaxation and crural diaphragm EMG inhibition along with the cranial motion of the crural diaphragm and the distal esophagus. CONCLUSIONS: There is a close temporal correlation between esophageal distension mediated LES relaxation and crural diaphragm inhibition with the sustained cranial motion of the crural diaphragm. Stretch caused by the longitudinal muscle contraction of the esophagus during distension of the esophagus may be important in causing LES relaxation and crural diaphragm inhibition.