Neurotransmitters and Inhibitory Actions
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Questions and Answers

What is the role of glutamine synthetase?

  • Releasing glutamate from synaptic vesicles
  • Activating ionotropic receptors
  • Converting glutamate to glutamine (correct)
  • Converting glutamine to glutamate

    • Which of the following is NOT a type of ionotropic receptor?

  • GABA (correct)
  • AMPA
  • NMDA
  • KA

    • What happens when NMDA receptors are activated?

  • Only Na+ and K+ are allowed to pass through
  • Only Ca2+ is allowed to pass through
  • No ions are allowed to pass through
  • Ca2+, Na+, and K+ are allowed to pass through (correct)

    • What is the function of VGLUT?

    <p>Achieving high concentrations of glutamate in synaptic vesicles</p> Signup and view all the answers

    What is the effect of domoic acid on the body?

    <p>It causes abdominal cramps, vomiting, diarrhea, and seizure</p> Signup and view all the answers

    What is the characteristic of AMPA receptors that lack the GluA2 subunit?

    <p>They are permeable to Na+, K+, and Ca2+</p> Signup and view all the answers

    What is the major inhibitory neurotransmitter in the brain?

    <p>GABA</p> Signup and view all the answers

    What is the effect of Picrotoxins on GABA receptors?

    <p>It blocks the effect of GABA</p> Signup and view all the answers

    What type of receptors do neurotransmitters involved in diffuse neuronal systems mainly act on?

    <p>Metabotropic receptors</p> Signup and view all the answers

    What is the function of inhibitory neurotransmitters?

    <p>They inhibit the cascade of action potential</p> Signup and view all the answers

    Which of the following is an example of an amino acid neurotransmitter?

    <p>Glutamate</p> Signup and view all the answers

    What is the process by which glutamate is released into the synaptic cleft?

    <p>Ca2+ dependent exocytosis</p> Signup and view all the answers

    What is a characteristic of neuropeptides in the CNS?

    <p>They are involved in a wide range of CNS functions</p> Signup and view all the answers

    What is the effect of a lack of orexin or its receptors in animals?

    <p>Narcolepsy and disrupted sleep-wake patterns</p> Signup and view all the answers

    What is the primary use of Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs)?

    <p>Treatment of pain disorders including neuropathies and fibromyalgia</p> Signup and view all the answers

    What is the primary function of endocannabinoids in the brain?

    <p>Activating a specific cannabinoid receptor</p> Signup and view all the answers

    What is a common symptom of Major Depressive Disorder?

    <p>Disturbances in sleep and appetite</p> Signup and view all the answers

    What is the characteristic of fluvoxamine?

    <p>Potent inhibitor of CYP2D6</p> Signup and view all the answers

    What is the enantiomer of citalopram?

    <p>Escitalopram</p> Signup and view all the answers

    What is the role of orexin neurons in the sleep-wake cycle?

    <p>They exhibit firing patterns associated with wakefulness</p> Signup and view all the answers

    What is a function of somatostatin, a type of neuropeptide?

    <p>Involvement in reproduction</p> Signup and view all the answers

    What is the primary use of Tricyclic Antidepressants (TCAs)?

    <p>Treatment of depression that is unresponsive to more commonly used antidepressants</p> Signup and view all the answers

    What is the characteristic of trazodone?

    <p>Weak but selective inhibitor of SERT with little effect on NET</p> Signup and view all the answers

    What is the characteristic of paroxetine?

    <p>Selective Serotonin Reuptake Inhibitor</p> Signup and view all the answers

    What is a common thought pattern in individuals with depression?

    <p>Thoughts of guilt, worthlessness, and suicide</p> Signup and view all the answers

    What is a common comorbidity associated with depression?

    <p>Coronary artery disease, diabetes, and stroke</p> Signup and view all the answers

    What is the primary use of antidepressants?

    <p>Treatment of major depressive disorder (MDD)</p> Signup and view all the answers

    What is the role of neurotrophic factors in the neurotrophic hypothesis of depression?

    <p>Enhancement of synaptic connectivity and neurotrophic support</p> Signup and view all the answers

    What is the hippocampus primarily responsible for?

    <p>Regulation of contextual memory and hormone release</p> Signup and view all the answers

    What is the outcome of effective antidepressant therapies on neurogenesis and synaptic connectivity?

    <p>Increased neurogenesis and synaptic connectivity</p> Signup and view all the answers

    Study Notes

    Glutamate and Glial Cells

    • Released glutamate acts on post-synaptic glutamate receptors.
    • Glutamate is converted to glutamine in glial cells by the enzyme glutamine synthetase.
    • In glia, glutamine is converted back to glutamate by the enzyme glutaminase.

    Vesicular Transport and Excitation

    • High concentrations of glutamate in synaptic vesicles are maintained by the vesicular glutamate transporter (VGLUT).
    • Nearly all tested neurons are excited by glutamate through activation of ionotropic and metabotropic receptors.

    Ionotropic Receptors

    • Three main types of ionotropic receptors: AMPA, Kainic Acid (KA), and NMDA.
    • AMPA receptors (contain GluA2 subunit) are permeable to Na+ and K+, but not Ca2+; some interneurons without GluA2 are Ca2+ permeable.
    • KA receptors are permeable to Na+ and K+, and can be Ca2+ permeable depending on subunit composition.
    • Domoic acid from shellfish can cause poisoning through excitatory action on KA and AMPA receptors, leading to symptoms like seizures.
    • NMDA receptors are ubiquitous in the CNS, allowing Na+, K+, and Ca2+ permeability; they require extreme depolarization to open.

    Inhibitory Neurotransmitters

    • GABA and Glycine serve as primary inhibitory neurotransmitters.
    • GABA is the major neurotransmitter in the brain, while Glycine is predominant in the spinal cord.
    • Picrotoxins block GABA's effects by binding to GABA-A receptors causing convulsions.

    Diffuse Neuronal Systems

    • These systems have broad distribution and varied activities, innervating multiple CNS regions.
    • Neurotransmitters involved include norepinephrine, dopamine, and serotonin (5HT), affecting a range of functions like sleep, attention, and emotional states.
    • Primarily activate metabotropic receptors for long-lasting synaptic effects.

    Neurotransmitter Categories

    • Excitatory neurotransmitters trigger action potentials.
    • Inhibitory neurotransmitters inhibit action potential transmission.
    • Major amino acid neurotransmitters include glutamate, GABA, and glycine.

    Neuropeptides and Functions

    • Neuropeptides co-exist with conventional neurotransmitters, influencing functions such as reproduction, social behavior, appetite, pain, and learning.
    • Opioid peptides like enkephalins and endorphins are included.

    Orexin/Hypocretins

    • Produced in the hypothalamus, orexins are excitatory neurotransmitters that regulate wakefulness and energy homeostasis.
    • Lack of orexin or its receptors leads to narcolepsy and disturbed sleep patterns.

    Other Signaling Substances

    • Endocannabinoids are psychoactive compounds affecting cognition and pain perception.
    • Nitric oxide and purines (ATP, UTP, adenosine) also act as signaling molecules in the CNS.

    Antidepressant Agents

    • Major Depressive Disorder (MDD) presents with persistent depressed mood, loss of interest, sleep and appetite disturbances, and cognitive deficits.
    • Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine and escitalopram have varying half-lives and inhibit cytochrome P450 enzymes.
    • Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) include venlafaxine and duloxetine, treating pain disorders and anxiety.

    Tricyclic Antidepressants (TCAs)

    • TCAs like imipramine and amitriptyline are used for treatment-resistant depression.
    • 5HT2 receptor modulators such as trazodone block 5HT2A receptors and are often prescribed as sleep aids.

    Tetracyclic and Unicyclic Antidepressants

    • Similar to TCAs but infrequently prescribed.
    • Depression increases risks for coronary artery disease, diabetes, and stroke.

    MDD Pathophysiology

    • Monoamine hypothesis suggests low monoamine levels in MDD.
    • Neurotrophic hypothesis emphasizes the role of neurotrophic factors in neural plasticity and resilience.
    • Brain-derived neurotrophic factor (BDNF) links effective antidepressant therapy to neurogenesis and synaptic connectivity, particularly in the hippocampus, which is crucial for memory and hormone release regulation.

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    Description

    This quiz covers the role of inhibitory neurotransmitters like GABA and Glycine, and how drugs interact with them, leading to effects like convulsions.

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