Cholinergic receptors:Nicotinic vs.Muscarinic The"Muscarinic actions"--reproduced by injection of muscarine,from Amanita muscaria. Similar to those of parasympathetic stimulation Multiple(5)muscarinic cholinergic receptors distributed in different tissues: Neural(M1):CNS,PNS,gastric parietal cells(excitatory;Gq) Cardiac(M2):atria conducting tissue;presynaptic(inhibitory;Gi) Glandular(M3):exocrine glands;smooth muscle (excitatory;Gq) Muscarinic receptors couple to G proteins Agonist t GEF Downstream D effectors GaGDP GaGTP PLC-B Ion channels Adenylyl cyclase GAP Kinases Pi Others 33 The “Muscarinic actions” -- reproduced by injection of muscarine, from Amanita muscaria. Similar to those of parasympathetic stimulation • Neural (M1): CNS, PNS, gastric parietal cells (excitatory; Gq) • Cardiac (M2): atria & conducting tissue; presynaptic (inhibitory; Gi) • Glandular (M3): exocrine glands; smooth muscle (excitatory; Gq) Cholinergic receptors: Nicotinic vs. Muscarinic Multiple (5) muscarinic cholinergic receptors distributed in different tissues: Gα•GDP GAP GEF Gα•GTP Muscarinic receptors couple to G proteins βγ βγ Pi Downstream effectors PLC-β Ion channels Adenylyl cyclase Kinases Others Agonist