These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Acetylcholine-induced desensitization of muscarinic contractile response in Guinea pig ileum is inhibited by pertussis toxin treatment.
    Author: Ehlert FJ, Ansari KZ, Shehnaz D, Sawyer GW, Griffin MT.
    Journal: J Pharmacol Exp Ther; 2001 Dec; 299(3):1126-32. PubMed ID: 11714903.
    Abstract:
    We investigated the effects of pertussis toxin treatment on acetylcholine-induced desensitization of the muscarinic contractile response in guinea pig ileum. Incubation of the isolated ileum with acetylcholine (30 microM) for 20 min caused a decrease in the sensitivity of the ileum to the contractile action of the muscarinic agonist oxotremorine-M. This desensitization was characterized by an increase in the EC(50) value of oxotremorine-M without a change in its maximal effect. A maximal 4- to 5-fold increase in the EC(50) value of oxotremorine-M was measured at the earliest time investigated after acetylcholine treatment (5 min), and normal sensitivity recovered within approximately 20 min after washout of acetylcholine. Treatment of the ileum with pertussis toxin caused a small increase in the contractile response to oxotremorine-M when measured without prior exposure to acetylcholine. After exposure to acetylcholine, little desensitization was observed in ilea that had been treated with pertussis toxin. Pertussis toxin-treatment caused a small increase in oxotremorine-M-mediated phosphoinositide hydrolysis and a large decrease in oxotremorine-M-mediated inhibition of forskolin-stimulated cAMP accumulation in slices of the longitudinal muscle of the ileum. Exposure of the ileum to acetylcholine had no desensitizing effect on the ability of oxotremorine-M to elicit phosphoinositide hydrolysis, indicating that the mechanism for desensitization of the contractile response occurs at a level downstream from the receptor and phosphoinositide hydrolysis. Our results suggest that activation of muscarinic receptors coupled to pertussis toxin-sensitive G(i) and G(o) is required for most of the desensitization observed in this study.
    [Abstract] [Full Text] [Related] [New Search]