Effects of Prostanoids and Indomethacin on Isolated Smooth Muscle from the Human Lower Oesophagus

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Abstract
Smooth muscle strips representing the longitudinal and the circular muscle layers of the oesophageal body and the oesophagogastric junction of the human oesophagus were mounted in organ baths and isometric tension recorded. Transmural field stimulation was applied to strips from both layers of the oesophageal body and to strips from the longitudinal muscle layer of the oesophagogastric junction. This resulted in contractions after cessation of the stimulus train in circular muscle, and in contractions during stimulation in longitudinal muscle preparations. Indomethacin lowered active tension in strips from the circular muscle layer of the oesophagogastric junction, and decreased responses to transmural field stimulation in all strips from the longitudinal muscle layer. The response to transmural field stimulation was increased in strips from the circular muscle layer of the oesophageal body, suggesting an inhibitory function of endogenous prostanoids in this muscle layer. Prostaglandin (PG) F2 alpha and the thromboxane A2 mimic U-46619 increased the responses to transmural field stimulation in all muscle types and the active tension in circular muscle from the oesophagogastric junction. PGE1 and PGE2 increased the responses to transmural field stimulation strips from the longitudinal muscle layer. In circular muscle strips from the oesophageal body responses to transmural field stimulation were inhibited. PGE1 decreased active tension in circular muscle strips from the oesophagogastric junction, whereas PGE2 produced inconsistent effects. These results suggest a role of prostanoids in the regulation of neuromuscular function in the human lower oesophagus. Moreover, exogenous prostaglandins may modulate oesophageal motor function.