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A comparative study of acetylcholine on the function and morphology of lower esophageal sphincter and esophageal body in rabbits

AIM: To compare the morphology of lower esophageal sphincter (LES) and esophageal body, and to explore the response of contraction of the smooth muscle of LES to acetylcholine (ACh).

METHODS: The morphology of LES and esophageal body was examined under light microscope and electron microscope. The pressures of LES and the esophageal body were measured. The concentration of Ca²⁺ was determined with laser scanning confocal microscopy before and after ACh was administrated.

RESULTS: The sarcoplasmic reticulum and myofilament were significantly increased in smooth muscle cells of LES. The pressures were 1.40.1 kPa and 0.60.1kPa for LES and esophageal body, respectively, and there was significant difference between them (P < 0.01). The mean concentrations of Ca²⁺ were 156.1±4.8 and 122.6±4.3 nmol/L (P < 0.05) in LES and esophageal body respectively before the application of ACh, and they became 241.3±5.7 nmol/L and 131.6±3.2 nmol/L after ACh was applied. The changed concentration of Ca²⁺ in LES was significantly higher (P < 0.01).

CONCLUSION: Esophageal body and LES utilize Ca²⁺ from different sources to contract in response to Ach. In esophageal body, Ach-induced contraction requires influx of extracellular Ca²⁺, while in LES it might utilize intracellularly released Ca²⁺.