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Ionotropic & Metabotropic Receptors Lesson 12 Membrane Proteins: Ionophores Ion Channels Non-gated always open Gated chemically-gated electrically-gated mechanically-gated ~ Chemically-Gated Channels Ligand-Receptor binding Ligand neurotransmitters drugs Receptor proteins ligand binds to multiple receptors receptor subtypes specificity ~ Ligand-Receptors Binding Binding site specific point of ligand & receptor Affinity attraction physical & electrical fit NT or drug binds to receptor or activity of neuron excite or inhibit Drugs mimic or block NT message ~ Lock & Key Model NT binds to receptor NT = key Receptor = lock Receptor changes shape Excitation or Inhibition? Determined by nature of receptor NOT NT ~ Receptor Subtypes Specificity Same NT Binds to many receptor subtypes Produce different effects EPSP or IPSP All NT systems Several subtypes each Drug side effects ~ ligand binds to receptor activation: EPSP or IPSP NT Receptor A ~ Same NT can bind to different -R different part of NT ~ NT Receptor A Receptor B Same NT can bind to different -R different part of NT ~ NT Receptor A Receptor B Same NT can bind to different -R different part of NT ~ NT Receptor A Receptor B Ionotropic receptors Ligand-gated channels Ion channels NT directly controls channel fast action transient ~ Metabotropic Receptors Requires energy GTP Neuromodulation G protein-gated Ion Channels Receptor indirectly controls channel relatively fast, but slower than ionotropic ~ G protein-gated Ion Channels R G GDP G protein-gated Ion Channels R G GTP G protein-gated Ion Channels R G GTP Pore Metabotropic receptors: 2d messenger systems 2d messenger systems Effects relatively slow long-lasting Signal amplification Effects Control channel Alter properties of receptors regulation of gene expression ~ 2d Messenger Systems Signal amplification 1 NT activate enzyme ATP 1000s cAMP 10,000s cAMP 10,000s phosphates ~ 2d Messenger Systems External signal NT = 1st messenger Membrane-associated components Receptor Transducer Primary effector Intracellular 2d messenger Secondary effector ~ external signal: nt Receptor transducer primary effector 2d messenger secondary effector 2d Messenger Systems Primary Effector Enzyme R G GTP * GDP Secondary Effector 2d Messenger Systems Primary Effector Enzyme R G GTP Secondary Effector 2d Messenger Systems Primary Effector Enzyme R G ATP GTP cAMP Secondary Effector 2d Messenger Systems Primary Effector Enzyme R G ATP GTP cAMP Secondary Effector P 2d Messenger Systems Primary Effector Enzyme R G ATP GTP P cAMP Secondary Effector Pore