Neuropharmacology - Psychopharmacology BRW: Chapter 4 Otto...

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Unformatted text preview: Psychopharmacology BRW: Chapter 4 Otto Loewis Experiment ( 1921 ) : Electrical vs. Chemical Transmission at the Synapse? Dish A Frog heart kept alive in fuid medium ( 1 ) Electrically Stimulate Vagus Nerve Dish B ( 3 ) Extract fuid ( 5 ) Heart slows ( 2 ) Heart slows Vagus Nerve Vagus Nerve ( 4 ) Inject fuid Criteria for demonstrating neurotransmitter function Chemical exists in presynaptic terminals Enzymes that synthesize chemical exist in the presynaptic terminals. Chemical is released ( in appropriate amounts ) when action potential reaches axon terminals. SpeciFc receptors exist on the postsynaptic membrane. Experimental application of the chemical ( in appropriate amounts ) produces postsynaptic potentials. Blocking release of chemical prevents presynaptic activity from altering postsynaptic activity. Criteria for demonstrating neurotransmitter function Chemical exists in presynaptic terminals Enzymes that synthesize chemical exist in the presynaptic terminals. Chemical is released ( in appropriate amounts ) when action potential reaches axon terminals. SpeciFc receptors exist on the postsynaptic membrane. Experimental application of the chemical ( in appropriate amounts ) produces postsynaptic potentials. Blocking release of chemical prevents presynaptic activity from altering postsynaptic activity. Binding a nity Agonists and Antagonists Agonist : A molecule, usually a drug, that binds a receptor and initiates a response like that of another molecule, usually a neurotransmitter. Antagonist : A molecule, usually a drug, that interferes with or prevents the action of a neurotransmitter. Competitive ligand : A drug that binds to the same site as the endogenous neurotransmitter Noncompetitive ligand : A drug that does not compete directly with the endogenous neurotransmitter, but rather binds to a modulatory site on the receptor. Drugs a f ect each stage of neural conduction and synaptic transmission: Presynaptic mechanisms Ca f eine : Competes with adenosine for A2 autoreceptors to inhibit the release of catecholamines ( e.g., norepinephrine ) . Adenosine is normally co- released with Axonal transport inhibited and enzymes prevented from reaching terminals Colchicine disrupts microtubules Enzymes for synthesis of neurotransmitters blocked PCPA blocks synthesis of serotonin Conduction of action potentials blocked Tetrodotoxin from ovaries of pufferfish blocks voltage- gated sodium channels Inhibit storage of transmitter Reserpine causes synaptic vesicles to become leaky Prevent transmitter release Botulinum toxin ( Botox ) blocks Ca 2+- dependent release of ACh Tetanus toxin blocks release at inhibitory synapses, resulting in strong involuntary contractions of...
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This note was uploaded on 04/29/2010 for the course PSYCH 002 taught by Professor Freeman during the Spring '08 term at University of Iowa.

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Neuropharmacology - Psychopharmacology BRW: Chapter 4 Otto...

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