Neurotransmitters and Receptors Overview
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Questions and Answers

Which of the following ion channels are responsible for neuronal activation?

  • Ligand-gated K+ channels
  • Voltage-gated Na+ channels (correct)
  • Voltage-gated K+ channels
  • Ligand-gated Cl- channels

    • What is the primary function of the alpha subunit of a metabotropic receptor?

  • Releasing neurotransmitters from vesicles
  • Activating downstream effectors (correct)
  • Binding to neurotransmitters
  • Directly modulating ion channels

    • Which of the following is NOT a step involved in neuronal signal transmission?

  • Synthesis of neurotransmitters in the postsynaptic neuron (correct)
  • Activation of postsynaptic receptors
  • Action potential arrival at the presynaptic terminal
  • Neurotransmitter re-uptake

    • What effect does the influx of chloride ions (Cl-) have on the neuron?

    <p>Hyperpolarization (C)</p> Signup and view all the answers

    Which type of receptor directly triggers ion channel opening?

    <p>Ionotropic receptors (D)</p> Signup and view all the answers

    What is the role of calcium ions (Ca++) in neurotransmitter release?

    <p>Ca++ ions trigger the fusion of synaptic vesicles with the plasma membrane (C)</p> Signup and view all the answers

    How are neurotransmitters typically removed from the synaptic cleft?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following is NOT a class of neurotransmitters?

    <p>Steroid hormones (D)</p> Signup and view all the answers

    Which of the following is NOT a true statement about the glutamate receptor sub-type AMPA/kainate?

    <p>Its primary effect is calcium influx. (A)</p> Signup and view all the answers

    Which of the following is a key factor in the reuptake of glutamate into presynaptic neurons?

    <p>Sodium dependence. (D)</p> Signup and view all the answers

    Which type of glutamate receptor is primarily responsible for slower neuronal depolarization?

    <p>NMDA receptor. (B)</p> Signup and view all the answers

    Which of the following is NOT a mechanism of glutamate synthesis?

    <p>Conversion from pyruvate via aminotransferases. (C)</p> Signup and view all the answers

    What is the primary mechanism by which metabotropic glutamate receptors (mGluRs) exert their effects?

    <p>Activation of G proteins. (C)</p> Signup and view all the answers

    What is the name of the enzyme that converts L-dopa to dopamine?

    <p>Aromatic L-amino acid decarboxylase (D)</p> Signup and view all the answers

    Which of the following drugs is a dopamine agonist?

    <p>Pramipexole (B)</p> Signup and view all the answers

    Which of the following drugs is a benzodiazepine?

    <p>Alprazolam (C)</p> Signup and view all the answers

    Which of the following drugs is a selective serotonin reuptake inhibitor (SSRI)?

    <p>Fluoxetine (C)</p> Signup and view all the answers

    Which of the following drugs is a non-selective β-blocker?

    <p>Propranolol (B)</p> Signup and view all the answers

    Which of the following drugs is a calcium channel blocker?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following drugs is an angiotensin-converting enzyme (ACE) inhibitor?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following drugs is a diuretic?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following drugs is a statin?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following drugs is a metformin?

    <p>Metformin (D)</p> Signup and view all the answers

    Which neurotransmitter is synthesized from glutamate?

    <p>GABA (C)</p> Signup and view all the answers

    What type of receptor is GABAB classified as?

    <p>Metabotropic receptor (C)</p> Signup and view all the answers

    What is the primary ion that flows through the GABAA receptor?

    <p>Chloride (Cl-) (A)</p> Signup and view all the answers

    Which enzyme is involved in the metabolism of serotonin?

    <p>MAO (D)</p> Signup and view all the answers

    What type of effects do GABAA receptors produce?

    <p>Inhibitory (B)</p> Signup and view all the answers

    Which neurotransmitter is derived from tryptophan?

    <p>Serotonin (D)</p> Signup and view all the answers

    Which of the following correctly describes the role of SERT?

    <p>Facilitates reuptake of serotonin (C)</p> Signup and view all the answers

    What is the physiological effect of presynaptic GABAB receptors on calcium conductance?

    <p>Decreases Ca2+ conductance (A)</p> Signup and view all the answers

    Which of the following is NOT a common neurotransmitter?

    <p>Glucose (B)</p> Signup and view all the answers

    What is the enzyme responsible for the breakdown of Acetylcholine?

    <p>Acetylcholine Esterase (C)</p> Signup and view all the answers

    Which type of receptors are involved in depolarization by Acetylcholine?

    <p>Nicotinic (A)</p> Signup and view all the answers

    Which type of muscarinic receptors is excitatory?

    <p>M1, M3, and M5 (A)</p> Signup and view all the answers

    What is the primary function of the choline transporter?

    <p>Transports choline back into the presynaptic neuron (A)</p> Signup and view all the answers

    Which of the following events is NOT involved in the depolarization caused by acetylcholine binding to nicotinic receptors?

    <p>The receptor stimulates G-protein activation. (B)</p> Signup and view all the answers

    How does the activation of M2 muscarinic receptors affect the cell?

    <p>Decreases cAMP levels (A)</p> Signup and view all the answers

    What is the significance of multiple binding sites on the nicotinic acetylcholine receptor?

    <p>It increases the sensitivity of the receptor to acetylcholine. (D)</p> Signup and view all the answers

    What is the primary mechanism of action (MOA) of benzodiazepines on the GABA-A receptor?

    <p>They act as positive allosteric modulators. (B)</p> Signup and view all the answers

    Which drug class primarily binds to the alpha subunit of the GABA-A receptor?

    <p>Benzodiazepines (D)</p> Signup and view all the answers

    How do barbiturates differ from benzodiazepines in their effect on the GABA-A receptor?

    <p>Barbiturates increase ion flux in the absence of GABA. (A)</p> Signup and view all the answers

    Identify the primary clinical use of flumazenil.

    <p>To reverse benzodiazepine overdose. (C)</p> Signup and view all the answers

    Which of the following statements about the pharmacokinetics of barbiturates is true?

    <p>Long-acting barbiturates are strong inducers of several CYP enzymes. (D)</p> Signup and view all the answers

    Which of the following benzodiazepines has the shortest duration of action?

    <p>Midazolam (B)</p> Signup and view all the answers

    What distinguishes Z-drugs from traditional benzodiazepines?

    <p>Z-drugs specifically target only the alpha-1 subunit. (C)</p> Signup and view all the answers

    What is a common side effect of barbiturates?

    <p>Drowsiness and confusion (C)</p> Signup and view all the answers

    Which mechanism of action is shared by both barbiturates and benzodiazepines?

    <p>They both act as positive allosteric modulators. (C)</p> Signup and view all the answers

    Which of the following is true regarding the biological half-lives of benzodiazepines?

    <p>They vary significantly depending on the specific drug. (B)</p> Signup and view all the answers

    Which drug is classified as a melatonin receptor agonist?

    <p>Ramelteon (B)</p> Signup and view all the answers

    What defines a major side effect of Z-drugs?

    <p>Drowsiness the next day (D)</p> Signup and view all the answers

    Which condition is treated with buspirone?

    <p>Generalized anxiety disorder (C)</p> Signup and view all the answers

    What is the primary neurotransmitter associated with GABA-A receptors?

    <p>GABA (B)</p> Signup and view all the answers

    Study Notes

    Neurotransmitters and Receptors

    • Neurotransmitters (NTs) and neuromodulators are covered in Ganong's Review of Medical Physiology, chapter 7; Basic & Clinical Pharmacology (chapters 21 & 23), 15th ed. by Katzung; Foye's Principles of Medicinal Chemistry (chapters 6 & 8), 8th ed.; and Goodman & Gilman's: Pharmacological Basis of Therapeutics (chapters 14 & 23), 13th ed.
    • Lecture objectives include describing neuronal structure, NT/neuropeptide synthesis, excitatory/inhibitory neuronal transmission, NT classes and their effects, catecholamine/acetylcholine synthesis/metabolism, the five steps of neuronal signal transmission, and the effects of pharmacological agents on neuronal signaling.
    • Ion channels (voltage-gated and ligand-gated [ionotropic]) and metabotropic receptors (GPCRs) regulate neurotransmitter effects.

    Ion Channels/Neurotransmitter Receptors

    • Voltage-gated ion channels (A): Control ion flow across cell membranes in response to voltage changes.
    • Ligand-gated ion channels (ionotropic) (B): Open or close in response to the binding of a neurotransmitter.
    • Metabotropic receptors (GPCRs) (C): Activate intracellular signaling pathways upon neurotransmitter binding.
      • Alpha subunits activate downstream effectors.
      • Beta/gamma subunits directly modulate ion channels.
    • Membrane-delimited regulation of ion channels occurs through metabotropic receptors.
    • Second messengers regulate ion channels via receptors.

    Ion Flux/Ion Channel Regulation

    • Depolarization (neuronal activation): Influx of sodium (Na+) and/or calcium (Ca2+).
    • Hyperpolarization (neuronal inhibition): Influx of chloride (Cl-) and/or efflux of potassium (K+).

    NT Release, Action, and Reuptake

    • Action potential (AP) triggers voltage-gated calcium (Ca2+) channels to open, causing neurotransmitter (NT) release into the synaptic cleft.
    • NTs bind to receptors on the postsynaptic membrane, causing a change in the neuron's membrane potential.
    • NTs are removed from the synapse via reuptake or enzymatic breakdown.

    Action Potentials/Excitatory and Inhibitory Signals

    • Simultaneous activation of excitatory synapses can lead to enough depolarization to generate an action potential (AP).
    • Integration of excitation and inhibition involves excitatory postsynaptic potentials (EPSPs), and inhibitory postsynaptic potentials (IPSPs) which can prevent an excitatory potential from reaching a threshold to stimulate depolarization.

    Specific Neurotransmitters & Receptors

    • Acetylcholine (ACh): Synthesized from choline and acetyl CoA; metabolized by acetylcholinesterase (AChE); receptors include muscarinic (GPCRs) and nicotinic (ligand-gated Na+ channels).
      • Muscarinic receptors (M1, M3, M5): Excitatory.
      • Muscarinic receptors (M2, M4): Inhibitory.
    • Dopamine: Catecholamine synthesized from tyrosine, metabolized by MAO and/or COMT; D1 & D5 are excitatory, D2-D4 are inhibitory.
    • Norepinephrine (NE): Catecholamine synthesized from tyrosine; metabolized by MAO and/or COMT; alpha1, beta1, and beta2 are excitatory; alpha2 is inhibitory.
    • Glutamate: Major excitatory neurotransmitter synthesized from glutamine. Receptors include inotropic AMPA/kainate and NMDA receptors, and metabotropic mGluR1-5.
    • GABA: Major inhibitory neurotransmitter synthesized from glutamate; metabolized by GABA-transaminase. Receptors include inotropic GABA-A (chloride [Cl-] channel) and metabotropic GABAB receptors.
    • Serotonin: Synthesized from tryptophan; metabolized by MAO; receptors include inotropic 5-HT3 receptors and metabotropic 5-HT1A/5-HT2a receptors.

    Drug Targets in Neurological Conditions

    • Drug targets include neurotransmitter synthesis, packaging, calcium channels, receptors, reuptake transporters, metabolism, release, and action potential modulation.
    • Specific drugs covered.

    GABA-A Receptor

    • Ligand-gated chloride (Cl-) channel; activation results in hyperpolarization, inhibiting nerve signal transmission.
    • Pentameric structure with two alpha subunits (six isoforms), and differing binding characteristics and effects.
    • Benzodiazepines, barbiturates and z-drugs are allosteric modulators of GABA-A receptor that enhances GABA binding and extends the duration of Cl- channel opening.

    Benzodiazepines

    • General anxiolytics, sedatives, hypnotics; bind to a site distinct from GABA and enhance GABA binding and increase duration/frequency of chloride channels.
      • Metabolism mainly via CYP3A4 and UGT1 glucuronidation, with exceptions for lorazepam, oxazepam, and temazepam.
      • Renal elimination is the major pathway for elimination.

    Drugs in Neuro Section

    • Drugs covered in the neuro section include various sedatives, hypnotics, anxiolytics, pain medications and other miscellaneous groups.

    Clinical Uses

    • Sedatives/hypnotics are used for insomnia, anxiety, alcohol withdrawal, medical/surgical procedures, trauma-induced coma, cancer-related sedation, epilepsy, and depression.

    Flumazenil

    • Competitive GABA-A receptor antagonist (BDZ antagonist), used as an antidote for high benzodiazepine overdose, short half-life, and rapid onset that is used to treat benzodiazepine overdose.

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    Description

    This quiz covers key concepts related to neurotransmitters and receptors, including neuronal structure, NT synthesis, and signal transmission. It references essential chapters from Ganong's Review of Medical Physiology, Basic & Clinical Pharmacology, and other pharmacological texts. Test your knowledge on excitatory and inhibitory transmission and the role of ion channels.

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