Altered contractile responsiveness in ileal longitudinal muscle after total gastrectomy in a rat model
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Purpose To test the hypothesis that the changes in ileal smooth muscle contractility accompanying postgastrectomy syndromes are agonist-specific, we investigated the effects of potassium chloride (KCl), carbachol, substance P (SP), and serotonin on ileal smooth muscle contractility after total gastrectomy in rats. Methods. We performed total gastrectomy in ten rats and a sham operation in another ten rats as a control. All of the rats were killed and their ileums excised 4 weeks postoperatively. The concentration-response relationships for KCl, SP, and serotonin were obtained by adding each agent cumulatively to the organ bath. Morphological changes in the ileum were also examined by light microscopy. Results. There was no significant difference between the responsiveness of gastrectomized and control tissues to KCl. Maximum responses (E-max) to carbachol and SP were less in the gastrectomized ileal segments than in the control ileal segments. E-max to serotonin was higher in the gastrectomized ileal segments than in the control ileal segments. The pD(2)value, i.e., the negative logarithm of the concentration for the half-maximal response, EC50, for carbachol, SP, and serotonin was unchanged in the gastroctomized ileal segments and the control segments. Total gastrectomy also caused morphological changes in the ileum. Conclusions. These data indicate that the contractile response to various agents is altered after total gastrectomy and that receptor-mediated mechanisms may cause these changes.