Lack of effect of nitric oxide on KCl, acetylcholine and substance P induced contractions in ileal longitudinal muscle of the rat

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Abstract

The aim of this study was to determine whether an excess of nitric oxide (NO) (mimicked by addition of NO donors) might produce by itself changes in the contractile responses to acetylcholine (ACh), substance P (SP) and KCl in the longitudinal muscle of the rat ileum. We also studied the calcium handling properties of this tissue in presence of NO donors. The NO donors assayed sodium nitroprusside (SNP) and 3-morpholinosydnonimine hydrochloride (SIN-1), induced different responses. SNP caused an immediate contraction followed by a sustained relaxation, whereas SIN-1 induced an immediate relaxation followed by a contraction. Even after prolonged incubations (up to 90 min), the NO donors SNP and SIN-1 were unable to modify the ACh- and SP- concentration-response curves, as well as the response to 30mM KCl. The nifedipine-resistant component of the ACh-induced contraction was not modified in presence of SNP. Cyclopiazonic acid (CPA) induced a contraction that was not modified when the tissue was pre-incubated with SNP. Nifedipine caused a sharp relaxation when added during the CPA-induced contraction and, when added previously, it reduced the CPA-induced contractile response. It is concluded that NO excess is not, by itself, responsible for the altered responses to KCl, ACh and SP. The contractility changes observed in the longitudinal muscle of the rat ileum during inflammation could rather be related to the presence of other inflammatory mediators (C) 2000 Elsevier Science Inc.
Original languageEnglish
Pages (from-to)531-541
JournalLife Sciences
Volume67
DOIs
Publication statusPublished - 23 Jun 2000

Keywords

  • 3-Morpholinosydnonimine hydrochloride (SIN-1)
  • Cyclopiazonic acid
  • Longitudinal muscle
  • Nitric oxide
  • Rat ileum
  • Sodium nitroprusside

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