title: Role of M1 receptor in regulation of gastric fundus smooth muscle contraction.
abstract: BACKGROUND
  The subject of this study is determination of the influence of drugs on gastric fundus smooth muscle contraction induced by activation of muscarinic receptors M1. Experiments tested interactions between a receptor agonist, carbachol and muscarinic receptor antagonists, atropine and pirenzepine.
  
  
  METHODS
  Testing was conducted on tissues isolated from rat's stomach. Male Wistar rats with weight between 220 g and 360 g were anesthetized by intraperitoneal injection of urethane (120 mg/kg). The stomach was dissected, and later the gastric fundus was isolated. Tissue was placed in a dish for insulated organs with 20 ml in capacity, filled with Krebs fluid. Results contained in the study are average values ± SE. In order to determine statistical significance, the principles of receptor theory were used (Kenakin modification).
  
  
  RESULTS
  According to tests, carbachol, in concentrations ranging between 10(-8) M to 10(-4) M, in a dosage-dependent way induces gastric fundus smooth muscle contraction. Presented results indicate that carbachol meets the conditions posed to full agonists. On the other hand, atropine, a non-selective muscarinic receptor antagonist, causes a concentration-dependent shift of concentration-effect curve (for carbachol) to the right, maintaining maximum reaction. According to analysis of the curve determined, we can deduce that atropine meets the conditions posed to competitive antagonists. The use of pirenzepine, a competitive receptor agonist M1, causes shift of concentration-effect curve (for carbachol) to the right, maintaining maximum reaction.
  
  
  CONCLUSIONS
  From the testing conducted on the preparation of the gastric fundus we can deduce that atropine causes shift of concentration-effect curves for carbachol to the right. A similar effect is released by pirenzepine, selectively blocking muscarinic receptors of M1 type. The results indicate that in the preparation of the gastric fundus smooth muscle, M1 type receptors occur also postsynaptically.
authors.affiliation: Department of Pharmacology and Therapy, Collegium Medicum in Bydgoszcz. gajdi@o2.pl
authors.forename: Marta
authors.initials: M
authors.lastname: Gajdus
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Szadujkis-Szadurska
authors.forename: Leszek
authors.initials: L
authors.lastname: Szadujkis-Szadurski
authors.forename: Izabela
authors.initials: I
authors.lastname: Glaza
authors.forename: Rafał
authors.initials: R
authors.lastname: Szadujkis-Szadurski
authors.forename: Joanna
authors.initials: J
authors.lastname: Olkowska
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology*; D018679:Cholinergic Agonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005748:Gastric Fundus / Q000378:metabolism; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010890:Pirenzepine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D043643:Receptor, Muscarinic M1 / Q000502:physiology*; D013223:Statistics as Topic
chemical_list: D018679:Cholinergic Agonists; D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D010890:Pirenzepine; D001285:Atropine; D002217:Carbachol