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Keywords:

  • apamin;
  • c-Kit;
  • interstitial cells of Cajal;
  • lower oesophageal sphincter;
  • nitric oxide;
  • Ws/Ws rat

Abstract  The distribution of interstitial cells of Cajal (ICC) and neurotransmission were investigated in lower oesophageal sphincter (LES) circular muscle strips from Sprague–Dawley (SD) rats, Ws/Ws mutant rats and their wild-type (+/+) siblings. Intramuscular c-Kit-positive cells, confirmed to be ICC-IM by electron microscopy, were observed throughout both muscle layers from SD and +/+ rats. In contrast, c-Kit-positive, ultrastructurally typical ICC-IM were absent in Ws/Ws. LES strips from Ws/Ws rats showed increased spontaneous contractile activity. Strips from SD and +/+ rats, responded to electrical neuronal stimulation with a relaxation that was in part L-NNA and in part apamin sensitive, followed by a contraction which was decreased by atropine. In Ws/Ws rats, similar to +/+ rats, neurally mediated relaxation was L-NNA and apamin sensitive and the contraction was decreased by atropine. We conclude that in the rat LES, relaxation is mediated by NO and an apamin-sensitive mediator, and contraction primarily by acetylcholine. Despite the absence of c-Kit-positive ICC, nerve–muscle interaction can be accomplished likely by diffusion of neurotransmitters to the smooth muscle cells. The lack of c-Kit-positive ICC is related to an increase in the basal tone and spontaneous contractile activity. The presence of fibroblast-like ICC in Ws/Ws rats might represent immature ICC whose possible functions need further investigation.