title: Ventricular, but not atrial, M2-muscarinic receptors increase in the canine pacing-overdrive model of heart failure.
abstract: OBJECTIVE
  To investigate the effects of heart failure induced by chronic rapid ventricular pacing (six weeks) on canine atrial and ventricular muscarinic receptors.
  
  
  METHODS
  Dogs (n = 4) were fitted with a bipolar pacing electrode connected to a Medtronic pacemaker set at 240 stimuli/min. Pacing was maintained for six weeks. Tissue samples obtained from the left atrium and ventral wall of the left ventricle were frozen at -70 degrees C. Control tissue was obtained from normal dogs (n = 6) following anesthesia and thoracotomy. M2-muscarinic receptors were characterized and quantified in tissue micropunches using the hydrophilic ligand [3H] N-methyl-scopolamine (NMS).
  
  
  RESULTS
  Cardiac tissue bound [3H] NMS with the specificity of an M2 subtype. Tachycardia-induced heart failure did not affect atrial muscarinic receptors but signify left ventricular myocytes (control 160.0 +/- 10.0 fmol/mg protein versus heart failure 245.0 +/- 25.0 fmol/mg protein; P < 0.01).
  
  
  CONCLUSIONS
  Canine ventricular muscarinic receptors display a specificity for the M2 subtype. In contrast to previous work, tachycardia-induced heart failure was accompanied by an increase (+ 53%) in ventricular, but not atrial, M2 receptors compared with normal dogs.
authors.affiliation: Department of Obstetrics and Gynaecology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia.
authors.forename: M
authors.initials: M
authors.lastname: Wilkinson
authors.forename: A
authors.initials: A
authors.lastname: Giles
authors.forename: J A
authors.initials: JA
authors.lastname: Armour
authors.forename: R
authors.initials: R
authors.lastname: Cardinal
mesh_terms: D000818:Animals; D001665:Binding Sites; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D004195:Disease Models, Animal; D004285:Dogs; D005260:Female; D006325:Heart Atria / Q000473:pathology; D006333:Heart Failure / Q000209:etiology / Q000473:pathology*; D006352:Heart Ventricles / Q000473:pathology*; D008297:Male; D019832:N-Methylscopolamine; D011976:Receptors, Muscarinic / Q000032:analysis*; D012602:Scopolamine Derivatives
chemical_list: D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D019832:N-Methylscopolamine