title: Modulating activity of M1 receptor to the reaction of ileal smooth muscle.
abstract: BACKGROUND
  The subject of the study was determination of the effect of drugs on ileal smooth muscle contraction induced by activation of M(1) type muscarinic receptors. Drugs that have an effect on muscarinic receptors are divided to agonists, with close ties to the receptor and high internal activity and antagonists, with no internal activity. Conducted experiments tested interactions between a broad-spectrum agonist of muscarinic receptors, carbachol and a selective muscarinic receptor antagonist of M(1) type, pirenzepine.
  
  
  METHODS
  Testing was conducted on tissues isolated from rat's intestine. Male Wistar rats with weight between 220 g and 360 g were anesthetized by intraperitoneal injection of urethane (120 mg/kg). Concentration-effect curves were determined with the use of cumulated concentration method, in accordance with the van Rossum method (1963) in Kenakin modification (2006).
  
  
  RESULTS
  The purpose of the study was determination of concentration-effect curves for carbachol. This curve was compared with the curve of receptor occupation depending on concentration of this drug. Based on concentration-effect curves, the average value of EC(50) was calculated for carbachol, amounting to 2.44×10(-6) [M/l].
  
  
  CONCLUSIONS
  The results confirmed that atropine is effective in stopping contractions caused by carbachol, meeting the conditions of competitive antagonists. Atropine caused the shift of curves for carbachol to the right. Pirenzepine, selectively blocking muscarinic receptors of M(1) type gave similar results. It was proved that in the preparation of gastric fundus smooth muscle, M(1) type receptors occur not only presynaptically, but also postsynaptically.
authors.affiliation: Department of Pharmacology and Therapy, Collegium Medicum in Bydgoszcz. izaglaza@gmail.com
authors.forename: Izabela
authors.initials: I
authors.lastname: Glaza
authors.forename: Leszek
authors.initials: L
authors.lastname: Szadujkis-Szadurski
authors.forename: Rafał
authors.initials: R
authors.lastname: Szadujkis-Szadurski
authors.forename: Marta
authors.initials: M
authors.lastname: Gajdus
authors.forename: Joanna
authors.initials: J
authors.lastname: Olkowska
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007082:Ileum / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D010890:Pirenzepine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*
chemical_list: D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D010890:Pirenzepine; D002217:Carbachol