title: Effects of M1 and M2 receptor agonists and blockers on dog respiration.
abstract: OBJECTIVE
  To study the effects of M1 and M2 receptor agonists and blockers on dog respiration.
  
  
  METHODS
  Using thoracic respiratory transducer and RM-86 multipurpose polygraph to determine respiratory rate (RR), tidal volume (TV), and minute ventilation volume (MVV), and DH-100G blood gas analysis instrument to analyze pO2, pCO2 and pH.
  
  
  RESULTS
  Pilocarpine (Pil, an M1-R subtype agonist) 0.5, 1, and 2 mg.kg-1 iv caused increases in RR, MVV, and pO2, and a decrease in pCO2. The excitatory effects of Pil were antagonized by pretreatment with pirenzepine (Pir, 3 mg.kg-1, iv) and scopolamine (Sco, 2 mg.kg-1, iv). The iv injections of a novel M2-R subtype agonist, 6 beta-acetoxy nortropane (6 beta-AN) 2, 5, and 20 micrograms.kg-1 caused decreases in RR, MVV, and pO2 and an increase of pCO2. The actions of 6 beta-AN were antagonized by iv pretreatment with AF-DX116 ¿11-2 [[2-[(diethylamino)methyl]-1-piperidinyl] acetyl]-5, 11-dihydro-6H[2,3-b][1,4]benzodiazepine-6-one, 0.5 mg.kg-1¿ and atropine (Atr, 2 mg.kg-1). Similar results were obtained when smaller doses of Pil (0.2, 0.4, and 0.8 mg.kg-1) and 6 beta-AN (0.25, 0.5, and 1 microgram.kg-1) were injected into the vertebral artery. Pir and Sco also antagonized the excitatory effects of Pil, and AF-DX116 and Atr antagonized the inhibitory effects of 6 beta-AN on respiration.
  
  
  CONCLUSIONS
  Stimulating M1-R of the respiratory center caused excitation of the respiration while stimulating the M2-R subtype caused inhibition of the respiration.
authors.affiliation: Department of Pharmacology, Xuzhou Medical College, China.
authors.forename: B
authors.initials: B
authors.lastname: Yao
authors.forename: X Q
authors.initials: XQ
authors.lastname: Ge
authors.forename: J L
authors.initials: JL
authors.lastname: Zheng
authors.forename: W
authors.initials: W
authors.lastname: Qin
authors.forename: C F
authors.initials: CF
authors.lastname: Bian
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D004285:Dogs; D005260:Female; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009662:Nortropanes / Q000037:antagonists & inhibitors; D010862:Pilocarpine / Q000037:antagonists & inhibitors*; D010890:Pirenzepine / Q000031:analogs & derivatives / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects*; D012601:Scopolamine / Q000494:pharmacology
chemical_list: D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D009662:Nortropanes; D010862:Pilocarpine; C071344:6-acetoxynortropane; D010890:Pirenzepine; D012601:Scopolamine; C048593:otenzepad