Medical Pharmacology Chapter 6:  Autonomic Pharmacology: Cholinergic Drugs

• Signal Transduction: Comparison of Muscarinic and Nicotinc Receptors

  • Nicotinic Receptors characteristics:

    •  The receptor is a ligand-gated ion channels.

    •  Agonist effects at the receptor are blocked by tubocurarine.

    •  Receptor activation results in:

      • A rapid increases of Na⁺ and Ca²⁺ conductance (increased movement of these ions across the membrane).

      • Deplorization of the membrane (membrane potential becomes less negative).

      • Excitation.

    •  Subtypes based on differing subunit composition: Muscle and Neuronal Classification

  • Muscarinic Receptors characteristics:

    •  This receptor is a G-protein coupled receptor system.

      • "G Protein linked 2^nd Messengers, G protein coupled receptors, GPCRs"

        Attribution: "Dr. Joel" G Protein linked 2nd Messengers, G protein coupled receptors, GPCRs 3/21/2016. https://www.youtube.com/watch?v=3qR9B2JCT_s Med Immersion (https://www.youtube.com/channel/UC5MpSzULJdwGOkGqmkHMC8A)

    •  Compared to nicotinic receptors, muscarinic receptors exhibit slower responses.

    •  Agonist effects blocked by atropine

    •  At least five receptor subtypes have been described by molecular cloning.

      • Variants have distinct anatomical locations and differing molecular specificities

Lefkowitz, R.J, Hoffman, B.B and Taylor, P. Neurotransmission: The Autonomic and Somatic Motor Nervous Systems, In, Goodman and Gillman's The Pharmacological Basis of Therapeutics, (Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) The McGraw-Hill Companies, Inc.,1996, pp.112-137.