<prompt> Cholinergic drug which acts on heart by decrease in levels of cAMP and due to opening of K channels is-MethacholineOxotremorineBethanecholDMPP  <response>: Ans. a i.e., Methocholine Characteristics of important subtypes of muscarinic receptor M1M2M31. Location andFunction subservedAutonomicganglia:Gastricglands:CNS:Depolarization late EPSPHist, release, acid secretionLearning, memory motor functionsSA node ; Hyperpolarizatian, rate of impulse generationAV node: velocity of conductionAtrium: shortening of APD, contractilityVentricle: contractility slight receptors sparseCholinergic nerve endings: ACh release CNS: tremor, analgesiaVisceral smooth mtwce:contractionGiGo-protein coupledK channel opening, cAPMMethacholineMethoctramine, TripitramineVisceral smooth muscle contractionIris : constriction of pupilCiliary muscle: contractionExocrine glands: secretionVascular endothelium: release of NO -2. Nature3. Transducer machanism4. Agonists5. AntagonistsGq-protein coupledIP3DAG - T cytosolic Ca2PLA2 PG synthesisACN-343A, OxotremorinePirenzepine, TelenzepineGq-protein coupledIP3DAG - cytosolic Ca2PLA2 PG synthesis.BethanecholSolifenacin, DarifenacinRelativelv selectiveACh activates and atropine blocks all 3 subtypes of muscarinic receptors.The CNS contains all subtypes of muscarinic receptors, but Mi appear to predominate.Most smooth muscles and glands have both M2 and M3 subtypes; M3 predominates. 