PCOL 3-2 Monoamines
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Questions and Answers

Which neurotransmitters are classified as a catecholamine?

  • Melatonin, Serotonin
  • Melatonin, Serotonin, Dopamine
  • Serotonin, Dopamine
  • Noradrenalin, Adrenalin, Dopamine (correct)

    • What is the defining structural feature of monoamines?

  • Contain 2 aromatic rings connected to an amino group by a 3-carbon chain
  • Contain 1 aromatic ring connected to an amino group by a 2-carbon chain (correct)
  • Contain 1 aromatic ring connected to a carboxyl group by a 3-carbon chain
  • Contain 1 aliphatic ring connected to an amino group by a 2-carbon chain

    • Which cognitive processes are regulated by monoamines?

  • Long-term memory and logical reasoning
  • Visual perception and decision making
  • Emotional and arousal (correct)
  • Language processing and motor skills

    • Which enzyme is mainly involved in the synthesis of monoamine neurotransmitters?

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

    Where is the characteristic anatomical distribution of the synthesis of monoamine neurotransmitters?

    <p>Limited to a few subcortical or brainstem regions</p> Signup and view all the answers

    Which type of receptors do monoamine neurotransmitters mainly activate?

    <p>G protein-coupled receptors</p> Signup and view all the answers

    Which enzyme is primarily responsible for the synthesis of monoamine neurotransmitters?

    <p>Aromatic amino acid decarboxylase</p> Signup and view all the answers

    What is the characteristic anatomical distribution of the synthesis of monoamine neurotransmitters?

    <p>Limited to a few subcortical or brainstem regions projecting to multiple cortical and limbic target regions</p> Signup and view all the answers

    What is the main type of receptors activated by monoamine neurotransmitters?

    <p>G protein-coupled receptors (GPCRs)</p> Signup and view all the answers

    Which enzyme is responsible for the rate-limiting step in the synthesis of catecholamines?

    <p>Tyrosine hydroxylase</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of L-tryptophan to 5-HPT in the synthesis of indoleamines?

    <p>Tryptophan hydroxylase</p> Signup and view all the answers

    Which transporter is responsible for the storage of monoamine neurotransmitters into vesicles?

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

    What is the primary function of L-DOPA in the brain?

    <p>Increase DA synthesis in substantia nigra</p> Signup and view all the answers

    Which drug is known to compete with endogenous monoamines for vesicular storage?

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

    Which neurotransmitter is primarily targeted in substance abuse disorders, Parkinson’s, and schizophrenia?

    <p>Dopamine (DA)</p> Signup and view all the answers

    What is the therapeutic use of 5-HTP?

    <p>Treat depression, anxiety, insomnia</p> Signup and view all the answers

    Which transporter is responsible for the reuptake of serotonin?

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

    Which enzyme is specific for the degradation of dopamine only?

    <p>MAO-B</p> Signup and view all the answers

    Which drug competes with endogenous ligands at dopamine, norepinephrine, and serotonin transporters?

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

    Which class of drugs is used clinically in depression and Parkinson’s disease?

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

    Which CNS function/disease is NOT affected by monoamines, according to the text?

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

    Which neurotransmitter's degradation is not considered a good target due to its association with addiction?

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

    Which drug disrupts the storage of noradrenaline in the vesicular monoamine transporter by disrupting the H+ gradient?

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

    What is the primary effect of amphetamines on vesicular monoamine storage and release?

    <p>Disrupt vesicular monoamine storage by competing for VMAT</p> Signup and view all the answers

    Where are large amounts of noradrenaline and 5-HT released from in the brain?

    <p>In projection areas of varicosities</p> Signup and view all the answers

    What effect does cocaine have on dopamine action in the synapse?

    <p>Prolongs dopamine action in the synapse by blocking dopamine transporter</p> Signup and view all the answers

    What is the primary mode of active transport for monoamine reuptake into neurons?

    <p>High affinity Na+-dependent membrane transporter protein</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with the regulation of feeding and sexual behavior?

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

    Which neurotransmitter is specifically linked to the centrally-mediated control of autonomic function?

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

    Which neurotransmitter is primarily responsible for the regulation of temperature and blood pressure?

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

    Study Notes

    Catecholamines

    • Catecholamines include dopamine, norepinephrine, and epinephrine.
    • These neurotransmitters share the catechol structure, characterized by a benzene ring with two hydroxyl groups.

    Monoamines

    • The defining structural feature of monoamines is the presence of an amine group (-NH2) attached to an aromatic ring.
    • Monoamines regulate various cognitive processes, such as mood, arousal, memory, and learning.

    Synthesis of Monoamines

    • The main enzyme involved in synthesizing monoamine neurotransmitters is aromatic L-amino acid decarboxylase.
    • The synthesis of monoamine neurotransmitters primarily occurs in the brainstem and specific regions of the central nervous system.

    Receptors and Transport

    • Monoamine neurotransmitters predominantly activate G protein-coupled receptors (GPCRs).
    • The rate-limiting step in the synthesis of catecholamines is catalyzed by the enzyme tyrosine hydroxylase.

    Indoleamines Synthesis

    • The enzyme tryptophan hydroxylase catalyzes the conversion of L-tryptophan to 5-hydroxytryptophan (5-HPT) during indoleamine synthesis.

    Storage and Function

    • The vesicular monoamine transporter (VMAT) facilitates the storage of monoamine neurotransmitters into vesicles.
    • L-DOPA serves as a precursor to dopamine and is primarily used to treat Parkinson’s disease.

    Drug Interactions

    • Reserpine is known to compete with endogenous monoamines for vesicular storage, impairing their function.
    • Dopamine is primarily targeted in substance abuse disorders, Parkinson’s disease, and schizophrenia.

    Therapeutic Uses

    • 5-Hydroxytryptophan (5-HTP) is used therapeutically to increase serotonin levels, benefiting mood and sleep disorders.

    Reuptake and Degradation

    • The serotonin transporter (SERT) is responsible for the reuptake of serotonin into neurons.
    • Monoamine oxidase (MAO) is specific for the degradation of dopamine, while catechol-O-methyltransferase (COMT) degrades norepinephrine and epinephrine.

    Drug Competitions and Classes

    • Cocaine competes with endogenous ligands at dopamine, norepinephrine, and serotonin transporters, enhancing their synaptic actions.
    • Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs used clinically in treating depression and promoting neurotransmitter balance in Parkinson’s disease.

    Impact on CNS Functions

    • Monoamines are not significantly implicated in the regulation of pain pathways, indicating their selective roles in emotional and cognitive functions.
    • Endogenous cannabinoids' degradation is less of a therapeutic target due to their strong association with addiction.

    Miscellaneous Effects

    • The drug reserpine disrupts noradrenaline storage by interfering with the vesicular monoamine transporter through the H+ gradient.
    • Amphetamines enhance vesicular monoamine release, leading to increased neurotransmitter availability in synapses.

    Release and Action

    • Large amounts of noradrenaline and serotonin (5-HT) are released from specific nuclei in the brain, such as the locus coeruleus and raphe nuclei.
    • Cocaine enhances dopamine action in the synapse by inhibiting its reuptake, increasing its availability.

    Transport Mechanisms

    • The primary mode of active transport for monoamine reuptake into neurons occurs via specific membrane transporters.
    • Serotonin is primarily associated with the regulation of feeding and sexual behavior.
    • Norepinephrine is linked to the centrally-mediated control of autonomic functions, including stress responses.
    • Dopamine plays a crucial role in regulating temperature and blood pressure.

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    Description

    Test your knowledge on monoamines, a sub-class of neurotransmitters that play a crucial role in regulating cognitive processes such as emotions, arousal, and memory. Learn about their structure and function, as well as their significance in treating psychiatric and neurological disorders.

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