Neurotransmitters: GABA and Glycine
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Questions and Answers

Which antagonist selectively blocks GABA-A receptors?

  • Phaclofen
  • Bicuculline (correct)
  • 5-OG-saclofen
  • CACA

    • What distinguishes GABA-C from GABA-A in receptor composition?

  • GABA-C contains rho subunits. (correct)
  • GABA-C is sensitive to bicuculline.
  • GABA-C has five subunits.
  • GABA-C is a metabotropic receptor.

    • Which compound is NOT an agonist for GABA-B receptors?

  • GABA
  • Baclofen
  • Both A and B
  • Phaclofen (correct)

    • What is a key function of GABA-B receptors when activated?

    <p>Open potassium channels. (C)</p> Signup and view all the answers

    Which option describes the structure of GABA-B receptors?

    <p>Composed of two isoforms, GABA-B1 and GABA-B2. (A)</p> Signup and view all the answers

    How do GABA-B receptors contribute to cellular hyperpolarization?

    <p>By reducing calcium influx. (C)</p> Signup and view all the answers

    Which GABA receptor is specifically found in the retina?

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

    Which substance does not affect GABA-C receptor activity?

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

    What effect does GABA-B receptor activation have on the neuronal membrane?

    <p>It hyperpolarizes the membrane. (B)</p> Signup and view all the answers

    In presynaptic terminals, what is the outcome of activating GABA-B receptors?

    <p>Calcium inflow is reduced. (D)</p> Signup and view all the answers

    How do GABAergic terminals contribute to the balance of neurotransmitter release?

    <p>By reducing excess neurotransmitter release after activation. (D)</p> Signup and view all the answers

    What role do GABA-A and GABA-B receptors play during high-frequency stimulation in hippocampal circuitry?

    <p>They facilitate long-term potentiation (LTP). (A)</p> Signup and view all the answers

    Which action does GABA-B receptor activation NOT cause?

    <p>Increase in excitatory neurotransmitter release. (A)</p> Signup and view all the answers

    What is the effect of convulsants like Bicuculline on GABA-A receptors?

    <p>They inhibit GABA-A receptors. (B)</p> Signup and view all the answers

    What is the primary function of the feedback mechanism provided by presynaptic GABA-B receptors during high-frequency activation?

    <p>To reduce inhibitory interference. (D)</p> Signup and view all the answers

    What happens when glutamate binds to AMPA and NMDA receptors during synaptic transmission?

    <p>Excitatory postsynaptic potentials (EPSPs) are generated. (D)</p> Signup and view all the answers

    What action do skeletal muscle relaxants like Baclofen primarily perform?

    <p>Activate GABA-B receptors (A)</p> Signup and view all the answers

    Which of the following effects can ethanol produce in the body?

    <p>Excitement, unconsciousness, and coma (C)</p> Signup and view all the answers

    How does ethanol influence GABA-A receptors according to the context provided?

    <p>Enhances GABA-A receptor activity (A)</p> Signup and view all the answers

    GABA is considered excitatory in what context?

    <p>During early embryonic development (D)</p> Signup and view all the answers

    What is the effect of silencing GABA-B receptors in the context of ethanol?

    <p>Decreases inhibition on GABA release (C)</p> Signup and view all the answers

    What role does glycine play in relation to NMDA receptors?

    <p>Serves as a co-agonist (C)</p> Signup and view all the answers

    What happens with increasing concentrations of GABA when ethanol is added?

    <p>GABA current increases more than usual (B)</p> Signup and view all the answers

    Bicuculline blocks the activity of which type of receptors?

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

    What is the primary role of the vesicular inhibitory amino acid transporter (VIAAT)?

    <p>Transport both GABA and glycine (D)</p> Signup and view all the answers

    How does glycine affect GABA uptake according to the described mechanisms?

    <p>Inhibits GABA uptake (D)</p> Signup and view all the answers

    What happens to glycine's effect on neurons after 10 days postnatally?

    <p>It becomes inhibitory (C)</p> Signup and view all the answers

    Which substances are known to allosterically modulate glycine receptors?

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

    What type of inhibition does strychnine exert on glycine receptors?

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

    Which transporter is responsible for increasing intracellular Cl⁻ in the embryonic nervous system?

    <p>NKCC1 transporter (D)</p> Signup and view all the answers

    Which of the following receptor subunits are glycine receptors composed of?

    <p>α and β subunits (D)</p> Signup and view all the answers

    Which of the following substances does NOT enhance glycine receptor function?

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

    What is the primary role of GABA in neurotransmission?

    <p>Mediating inhibitory signals (A)</p> Signup and view all the answers

    Which enzyme is responsible for the synthesis of GABA from glutamate?

    <p>Glutamate acid decarboxylase (C)</p> Signup and view all the answers

    What is GAD-65 primarily associated with?

    <p>Expression in nerve axon terminals (A)</p> Signup and view all the answers

    Which type of GABA receptor is ionotropic and functions as a chloride ion channel?

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

    What happens to most GABA after it is released into the synaptic cleft?

    <p>It spills over into surrounding areas and is taken up by astrocytes (C)</p> Signup and view all the answers

    What is one of the outcomes of the influx of chloride ions through GABA-A receptors?

    <p>Hyperpolarization of the postsynaptic cell (A)</p> Signup and view all the answers

    What is primarily recycled back into glutamate by GABA transaminase enzymes?

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

    Which GABA receptor type is less common compared to GABA-A and GABA-B?

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

    Study Notes

    GABA and Glycine Neurotransmitters

    • GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter, while glutamate is an excitatory neurotransmitter. Interestingly, glutamate is a precursor to GABA.
    • GABA is synthesized by the enzyme glutamic acid decarboxylase (GAD), existing in two forms (GAD-65 and GAD-67).
    • GAD-65 is primarily found in nerve axon terminals, while GAD-67 is distributed throughout the cell body, dendrites, and spines. GAD-65 is connected to interneurons that guide promoters, aiding in identifying interneurons.
    • GABA is packaged into vesicles and released into the synaptic cleft during neurotransmission. Some GABA binds to GABA receptors on the postsynaptic cell, mediating inhibitory signals; however, much of it spills over into the surrounding area, and is taken up by astrocytes.
    • Within astrocytes, GABA is converted back to glutamate, which is then returned to the interneuron for reuse, thus recycling is efficient.
    • GABA receptors are of two main types: GABA-A and GABA-B, with GABA-C less prevalent.
    • GABA-A is an ionotropic receptor acting as a chloride ion channel. Activation by GABA (or agonists like muscimol) allows chloride ions (Cl-) to flow into the cell, leading to hyperpolarization. Antagonists include bicuculline and picrotoxin.
    • GABA-C is also ionotropic, like GABA-A, but with a different subunit composition and sensitivity to agonists and antagonists. A key difference is its sensitivity to CACA, but not bicuculline.
    • GABA-B is metabotropic, working through G-protein coupled receptors (GPCRs), causing slower, longer-lasting inhibitory effects.
    • GABA-B agonists include GABA and baclofen, whereas antagonists are phaclofen and 5-OG-saclofen.
    • GABA-A receptors are composed of five subunits which vary, creating functional diversity.
    • GABA-C is made from rho subunits (rho1, rho2, rho3).
    • GABA-B receptors are formed by the dimerization of two isoforms (GABA-B1 and GABA-B2).

    Basic Pharmacology of GABA Receptors

    • GABA receptors are targets for drugs and have different effects. Agonists enhance receptor activity and include GABA, other substances. Antagonists block receptor activity and include substances like bicuculline, picrotoxin, and CACA.
    • Various drugs influence GABA receptor function, including convulsants (enhancing activity) and skeletal muscle relaxants (reducing activity).

    GABA-B in Synaptic Transmission

    • GABA-B receptors are in both postsynaptic and presynaptic compartments and when activated, they close voltage-gated calcium channels, reducing neurotransmitter release through a feedback loop.
    • This regulation of neurotransmitter release maintains a balance in the system.
    • GABA-B receptors play a role in synaptic plasticity, especially during high-frequency activity.

    Drugs Affecting GABAergic Transmission

    • Convulsants like bicuculline inhibit GABA-A receptors, increasing neuronal activity.
    • Skeletal muscle relaxants like baclofen activate GABA-B receptors, reducing neuronal activity.

    Alcohol and GABA Receptors

    • Alcohol potentiates GABA receptor activity; enhancing their inhibitory effects.
    • Alcohol boosts inhibitory signalling, leading to sedative and depressant effects.
    • The effect is dose-dependent on GABA receptors, and the impact on glycine receptors.

    Glycine

    • Glycine is an inhibitory neurotransmitter.
    • It's a co-agonist for NMDA receptors.
    • Glycine is crucial for the maturation of neuronal circuits, and crucial for excitatroy/inhibitory shifts.
    • Glycine receptors are modulated by various molecules including alcohols and other drugs.

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    GABA and Glycine Neurotransmitters PDF

    Description

    Explore the roles of GABA and glycine as neurotransmitters in the nervous system. This quiz covers the synthesis, function, and recycling of GABA, as well as its interaction with receptors. Enhance your knowledge of these crucial inhibitory neurotransmitters.

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