Alterations in spontaneous contractions of rat proximal and distal colon after peritonitis
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Background/ Purpose: The aim of this study was to investigate the effect of peritonitis on spontaneous contractions of distal and proximal colon smooth muscle isolated from rats. Methods: Peritonitis was induced by cecal ligation and puncture in 8 rats. Another group of 8 rats : underwent a sham operation and acted as controls. Twenty-four hours after the operation, the rats were killed; and their distal and proximal colon smooth muscle was excised and placed in circular muscle direction in a 10-mL organ bath. Changes in the amplitude and frequency of contractions were analyzed before and after the addition of antagonists. Results: Peritonitis induced the increase in the amplitude and frequency of spontaneous contractions. In both distal and proximal colon of the control group, the amplitude of spontaneous contractions was elevated by N-G -nitro-L-arginine and tetradotoxin; but the frequency of spontaneous contractions was significantly elevated only in the presence of N-G-nitro-L-arginine. In both distal and proximal colon of the peritonitis group, the enhanced amplitude and frequency were significantly decreased and returned to control values in the presence of celecoxib. Conclusions: Peritonitis induces the increase in the amplitude and frequency of spontaneous contractions of distal and proximal colon, which can be attributed to a loss of inhibitor nitrergic and other neural control or rise of cyclooxygenase-2 levels. (c) 2007 Elsevier Inc. All rights reserved.