Influence of different intragastric stimuli on triggering of transient lower oesophageal sphincter relaxation in the dog.

Gastro-oesophageal reflux in the dog is mainly caused by transient lower oesophageal sphincter relaxation (TLOSR), the major stimulus for which is distension of the stomach. The possibility that liquid and/or acid sensors in the proximal stomach reduce the incidence and/or shorten the duration of TLOSR was addressed in the present study. Manometric recordings of the pharynx, oesophagus, lower oesophageal sphincter and stomach were made in awake dogs equipped with an oesophagostomy. TLOSRs were induced by insufflation of air or infusion of liquid nutrients with varying pH. Intragastric distension with air provoked TLOSRs with a significantly shorter duration than those seen after distension with liquid (4.3 +/- 0.5 vs 9.6 +/- 0.3 sec; P < 0.05). There were fewer TLOSRs at high intragastric pH (pH 5.0: 3.1 +/- 0.5/90 min) than at low pH (pH 1.5: 5.5 +/- 0.9/90 min, P < 0.05). Successfully propagated peristalsis following a TLOSR was more common after stimulation with liquid than with air. It can be concluded that there are H(+)-sensing mechanisms in the stomach which stimulate triggering of TLOSR. In addition, the reduced duration of TLOSR during air insufflation shows that the physical state of the distending stimulus can affect the patterning of TLOSR.