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Pharmacology 3001 > CNS Dopaminergic Neurotransmission - Kelly 5 > Flashcards

CNS Dopaminergic Neurotransmission - Kelly 5 Flashcards

1
Q

Dopaminergic pathways in the brain

A
  1. Mesolimbic pathway
  2. Mesocortical pathway
  3. Nigrostriatal pathway
  4. Tuberoinfundibular pathway
  5. Chemoreceptor trigger zone and regular emesis
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2
Q

Mesolimbic pathway

A

DA neurons in the tegmenjtum synapse at NcAc

Important in reward

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3
Q

Mesocortical pathways

A

Da neurons from tegmenjtum to prefrontal cortex

Important in cognition, motivation

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4
Q

Nigrostriatal pathway

A

DA neurons from Substance nigra synapse in striatum

Important in coordination of movement

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5
Q

Tuberinfundibular pathway

A

DA pathway from hypothalamus to pituitary Inhibits release of prolactin binding to increased serum prolactin

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6
Q

Drugs affecting dopaminergic pathways

A
  1. Drugs of abuse (mesolimbic pathways)
  2. Antipsychotics (mesolimbic and mesocortical pathways)
  3. Drugs for Parkinson’s disease (nigrostriatal pathway)
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7
Q

DA metabolism

A

Broken down by COMT and MAO to homovanillic acid

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8
Q

D1 receptor family

A

Increase cAMP via Gs
Increase PIP2 hydrolysis
Ca mobilization, PKC activity

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9
Q

D2 receptor family

A

Decrease cAMP via Gi
Increase K currents
Decrease voltage-gated Ca currents

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10
Q

Schizophrenia

A

1% of the worlds population

Positive, negative and cognitive symptoms

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11
Q

Positive symptoms of schizophrenia

A

Psychosis, with hallucinations and delusions

Caused by increase activity in mesolimbic pathway

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12
Q

Negative symptoms of schizophrenia

A

Social withdrawal, inability to experience pleasure, loss of motivation
Caused by decreased activity in mesocortical pathway

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13
Q

Cognitive symptoms of schizophrenia

A

Disorganization of thought and speech

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14
Q

Dopamine hypothesis of schizophrenia

A

May result from functional excess of dopamine in the CNS
Based on evidence that drugs that block DA receptors can relieves symptoms
Drugs that activate DA receptors aggravate symptoms and cause psychoses

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15
Q

Drug action for schizophrenia

A

Increase activity in mesocortical (5-HT receptor blockers), decrease activity in mesolimbic (D2 receptor blockers)

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16
Q

Antipsychotic drugs

A

Agents that reduce psychotic symptoms and improve behaviour of schizophrenia patients
Also called neuroleptic drugs because they suppress motor activity and emotion
Typical and Atypical

17
Q

Chlorprozamine

A

First anti-psychotic drug
Anti-histamine being tested as adjunct to anesthesia
Prevents hallucinations and delusions
Blocks D2 receptors

18
Q

Typical anti-psychotic drugs

A

First generation, or conventional
Phenothiazines (chlorpromazine)
Butyrophenones (haloperidol)
Ability to relieve positive symptoms of schizophrenia correlates with affinity for antagonism of D2 receptors
Block of D2 receptors in striatum results in extra-pyramidal side effects

19
Q

Atypical anti-psychotic drugs

A 
Clozapine, olanezepine
Higher affinity for 5-HT2 than for D2
Acts presynaptically to block DA release in prefrontal cortex
Reduces extrapyramidal side effects
Metabolic dysfunction
More expensive
20
Q

Anti-psychotic drug PK/PD

A

Well absorbed, with long half life, sequestered in body tissue
Dopamine receptor antagonism
Correlation between effective dose and binding affinity for D2 receptors

21
Q

Extrapyramidal dysfunction

A

Results from D2 receptor blockade
DA is a NT in the nigrostatial pathway
Stratum is part of the extrapyramidal motor system
Important in initiation and execution of voluntary movements
Management is reducing dose of antipsychotic

22
Q

Acute extrapyramidal side effects

A

Akathisia, pseudoparkinsonism, dystonia due to antagonism of DA receptors

23
Q

Long term extrapyramidal side effects

A

Tardive dyskinesia due to increased sensitivity of DA receptors

24
Q

Parkinsons disease

A

Nigrostriatal pathway
Progressive neurodegenerative disorder that affects motor pathways in the brain
Loss of dopaminergic neurons in the substantial nigra, leading to decreases DA in the striatum
Exact cause unknown
Progressive
Resting tremor, rigidity, akinesia, bradykinesia

25
Q

Treatment for Parkinsons

A
  1. Drugs that increase DA levels in the brain
  2. DA receptor agonists
  3. Acetylcholine antagonists
26
Q

Drugs that increase DA levels

A
  1. Levodopa
  2. Caridopa
  3. Catechol-O-methyltransferase inhibitors
  4. Selegiline
27
Q

Levodopa

A

L-DOPA
Biosynthetic precursor of DA
Crosses BBB and taken up by neurons in the substantial nigra
Covered into dopamine by LAAD
Can be metabolized in the periphery by LAAD and COMT to produce DA and 3OMD
Adverse affects due to increase DA in peripheral tissues

28
Q

Caridopa

A

Analog of L-DOPA
Inhibits conversion of L-DOPA to DA in the peripheral tissue
Does not cross BBB
Combination therapy with L-DOPA to increase the amount of L-DOPA that crosses the BBB, allowing lower amounts of L-DOPA

29
Q

Catechol-O-methyltransferase inhibitors

A

Block conversion of L-DOPA to 3-OMD
Used in combination with L-DOPA
Inhibits activity of COMT, the peripheral enzyme that metabolites L-DOPA to 3OMD
Maximizes bioavailability of L-DOPA to be transported into the brain

30
Q

DCC inhibitor

A

Events conversion of L-DOPA into dopamine in periphery

31
Q

Selegiline

A

Irreversible inhibitor of MAO-B in the stratum
Stratal MAO-B metabolizes DA
Inhibits oxidation of DA to DOPAC
Increases DA levels in stratum

32
Q

Dopamine receptor agonists

A

Directly activate DA receptors
Can be used in combination with levodopa-carbidopa
Act at most synaptic dopamine receptors
Activation of a specific DA receptor may limit adverse effects of these drugs

33
Q

Antimuscarinic drugs

A

Block stratal muscarinic receptors
Not as effective as levodopa-carbidopa treatment
Efficient at controlling tremors
Often used in combination therapy, alleviate extra-pyramidal effects caused by older anti-psychotic drugs

34
Q

Amantadine

A

Often combined with levodopa-carbidopa therapy
Also anti-viral
Used in patients who do not respond well to levodopa
Inhibits dopamine re-uptake
Facilitate presynaptic DA release
Antagonist NMDA receptors

35
Q

Pharmacological strategy in Parkinson’s disease

A

Enhance dopamine functions or antagonize acetylcholine at muscarinic receptors

Pharmacology 3001 (19 decks)

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