Drugs Affecting Central Nervous System
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Questions and Answers

Which of the following is NOT a cause of neuronal damage in neurodegenerative diseases?

  • Increased neuronal regeneration (correct)
  • Excessive excitotoxicity
  • Apoptosis
  • Oxidative stress

    • Dopaminergic neurons can regenerate after damage in the central nervous system.

    False

    Name one neurodegenerative disease mentioned.

    Parkinson's disease

    The nigrostriatal tract plays a key role in regulating _____ by releasing dopamine.

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

    Match the following dopaminergic pathways with their primary functions:

    <p>Nigrostriatal tract = Regulates movement Mesolimbic-mesocortical tract = Regulates cognitive functions Tuberoinfundibular pathway = Decreases prolactin secretion</p> Signup and view all the answers

    What is the primary reason large doses of L-dopa are required?

    <p>Over 90% is decarboxylated to dopamine in the periphery</p> Signup and view all the answers

    Carbidopa and Benserazide are unable to cross the blood-brain barrier.

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

    What is the effect of combining L-dopa with Carbidopa?

    <p>Increased availability of L-dopa to the CNS</p> Signup and view all the answers

    The enzyme that breaks down L-dopa in the periphery is called ______.

    <p>Dopa decarboxylase</p> Signup and view all the answers

    Match the following drugs with their functions:

    <p>Carbidopa = Inhibits peripheral dopa decarboxylase Benserazide = Selectively reduces peripheral dopamine formation Entacapone = COMT inhibitor used alongside L-dopa Tolcapone = Causes potential hepatotoxicity</p> Signup and view all the answers

    Which metabolite is produced when L-dopa is broken down by COMT?

    <p>3-O-methyldopa</p> Signup and view all the answers

    The effectiveness of the L-dopa/Carbidopa combination does not decline over time.

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

    What is the primary purpose of using carbidopa in combination with L-dopa?

    <p>To inhibit peripheral dopa decarboxylase</p> Signup and view all the answers

    Entacapone is a central COMT inhibitor.

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

    What phenomenon describes the fluctuations in motor response due to short half-life of L-dopa?

    <p>on-off phenomenon</p> Signup and view all the answers

    The combination treatment of L-dopa + Carbidopa + ________ is commonly used for Parkinson's disease.

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

    Match the following treatments with their mechanism:

    <p>Carbidopa = Inhibits peripheral dopa decarboxylase Entacapone = Inhibits peripheral COMT Tolcapone = Inhibits central and peripheral COMT Direct dopamine agonist = Stimulates dopamine receptors directly</p> Signup and view all the answers

    What is a significant side effect of Tolcapone?

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

    Increasing the frequency of L-dopa doses can help manage the wear-off phenomenon.

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

    What happens with chronic use of L-dopa regarding the dopaminergic neurons?

    <p>Most dopaminergic neurons degenerate.</p> Signup and view all the answers

    The gradual fading of improvement gained from a dose of levodopa is known as the __________ phenomenon.

    <p>wear-off</p> Signup and view all the answers

    What is the effect of high doses of catecholamines on the pupil?

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

    Levodopa is effective in patients who have not responded to dopamine receptor agonists.

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

    What is the primary concern with administering nonselective MAO inhibitors while on levodopa?

    <p>Hypertensive crisis</p> Signup and view all the answers

    Bromocriptine is derived from _______.

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

    Match the drug to its effect:

    <p>Levodopa = Increases dopamine levels Dopamine agonists = Stimulate D2 receptors Bromocriptine = Risk of pulmonary fibrosis Nonselective MAO inhibitors = Can cause hypertensive crisis</p> Signup and view all the answers

    Which of the following is an adverse effect common to both levodopa and dopamine agonists?

    <p>Nausea and vomiting</p> Signup and view all the answers

    Dopamine receptor agonists are known to significantly reduce motor fluctuations in advanced Parkinson's disease without the need for L-dopa.

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

    What is the main advantage of dopamine agonists over levodopa?

    <p>Do not result in significant motor fluctuations or dyskinesias</p> Signup and view all the answers

    Prolonged use of _______ may cause mental conditions to worsen in psychiatric patients.

    <p>Bromocriptine and l-dopa</p> Signup and view all the answers

    Study Notes

    Drugs Affecting the Central Nervous System

    • Neurodegenerative diseases involve neuronal damage in specific brain regions.
    • Causes include excessive excitotoxicity (excess glutamate), stroke, head trauma, oxidative stress (increased reactive oxygen species), and apoptosis (programmed cell death).
    • Neurodegenerative diseases are difficult to treat as CNS neurons cannot regenerate once damaged. Treatment is therefore symptomatic.
    • Examples of neurodegenerative diseases: Parkinson's, Alzheimer's, Huntington's, and Multiple sclerosis.

    Dopaminergic Pathways

    • Dopamine (DA) is a precursor to norepinephrine (NE) in noradrenergic pathways.
    • It's a neurotransmitter in:
      • Nigrostriatal tract: DA-releasing neurons project to the striatum, regulating movement by inhibiting GABA-ergic and cholinergic neurons.
      • Mesolimbic-mesocortical tracts: DA-releasing neurons projecting to limbic and cortical structures regulate cognitive functions.
      • Tuberoinfundibular tract: DA-releasing neurons from the hypothalamus regulate prolactin levels in the anterior pituitary.
      • Chemoreceptor trigger zone: DA receptor activation in the medulla increases vomiting.

    Parkinson's Disease

    • Parkinson's is a progressive neurological disorder of movement, second only to Alzheimer's disease in frequency.
    • Characterized by four cardinal motor features: resting tremors, muscular rigidity, bradykinesia (slow movement), and abnormal gait.
    • Occurs primarily in individuals over 65.
    • Etiology involves neurodegeneration in inhibitory dopaminergic neurons relative to excitatory cholinergic neurons in the nigrostriatal tract.
    • Imbalance between these causes the symptoms in Parkinson's disease.

    Parkinson's Disease Classification

    • Primary (idiopathic): More than 80% dopaminergic neuron degeneration in the substantia nigra leading to dopamine deficiency and increased acetylcholine.
    • Secondary (atypical): Often due to imbalances between acetylcholine and dopamine, including:
      • Vascular Parkinsonism (Small vessel cerebral ischemia)
      • Post-traumatic
      • Toxin-induced
      • Infectious
      • Drug-induced (e.g., antipsychotics)

    Treatment of Parkinson's Disease

    • Goal: Restoring the balance between acetylcholine and dopamine in the basal ganglia.
    • Treatment is symptomatic (temporary relief) and does not prevent disease progression.
    • Dopaminergic drugs: Levodopa (L-dopa) is the most common, converting to dopamine in the brain. Peripheral decarboxylase inhibitors (e.g., carbidopa) decrease peripheral dopamine, increasing levodopa reaching the brain.
    • Dopamine receptor agonists: Mimic dopamine's function, used in early stages or along with levodopa.
    • COMT inhibitors: (e.g. Entacapone) Prevent the breakdown of levodopa.
    • Anticholinergic drugs: Help reduce acetylcholine overstimulation, though not as effective as levodopa.

    Additional Details

    • On-off phenomenon: Fluctuations in levodopa's effect, causing periods of improved and impaired movement.
    • Dyskinesias: Involuntary movements, often a long-term consequence of levodopa therapy.
    • Adverse Effects: Levodopa may cause nausea, vomiting, dyskinesia, postural hypotension, and confusion.

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    Description

    This quiz explores the impact of drugs on central nervous system functions, focusing on neurodegenerative diseases and dopaminergic pathways. Participants will learn about causes of neuronal damage, examples of diseases, and the role of dopamine in regulating movement and cognition.

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