Basal Ganglia + Pharmacology Flashcards
Draw out the route of the direct pathway
See slides
Which receptor does dopamine act on in the direct pathway?
D1 receptors
Does the direct pathway promote or inhibit movement?
Promotes it
Describe the basic pathology of Parkinson’s disease
Less dopamine is released from the SNPC to activate the striatum by acting on D1 receptors in the direct pathway. Less activation of the direct pathway will result in decreased movement and Parkinson-isms
What 2 things make up the striatum?
Caudate nucleus
Putamen
What 3 things make up the pallidum?
Globus pallidus internus
Globus pallidus externus
Substantia nigra pars reticula
What 3 things make up the lentiform nucleus?
Putamen
Globus pallidus internus
Globus pallidus externus
What does the caudate nucleus connect with anteriorly?
Putamen
What does the substantia nigra pars compacta do in normal physiology?
Promotes movement
Activates direct pathway
Inhibits indirect pathway
What type of signalling does the substantia nigra pars compacta use?
Dopaminergic
What is an immediate lateral relation of the thalamus?
The internal capsule
Which portion of the thalamus connects the basal ganglia to the premotor cortex?
Ventral anterior nucleus
SNPC activates the striatum via…
D1 receptors
Direct pathway
SNPC inhibits the striatum via…
D2 receptors
Does the indirect pathway promote or reduce movement?
Reduces movement
Draw out the indirect pathway
See slides
Describe Huntington’s disease
Huntington’s causes degeneration of the striatal input to the GPE.
This switches off the inhibition from the GPE to the subthalamic nucleus
What does hyperkinetic mean?
Too much movement
What does hypokinetic mean?
Too little movement
Name some hypokinetic disorders (5)
Parkinson’s
Multiple systems atrophy
Progressive supranuclear palsy
Wilson’s disease (pseudoparkinsonism)
Essential tremor
Name some hyperkinetic disorders (7)
Hemiballismus
Huntington’s
Dystonias
Wilson’s disease (dystonic)
Essential tremor
Chorea
Athetosis
Define tremor
Shaking movements
Define dystonia
Twisting and repetitive movements or abnormal postures
Define athetosis
Writhing movements like a snake
Define chorea
Twitching or jerking a group of muscles
Define ballismus
Large, flinging limb movements
Define tics
Small involuntary movements
Which region is involved in Parkinson’s disease?
Which neurotransmitter is affected?
Substantia nigra
Reduction in dopamine
Which region is involved in Huntington’s disease?
Which neurotransmitter is affected?
Striatum (caudate nucleus + putamen)
Reduction in GABA
What is the inhibitory neurotransmitter in the basal ganglia?
GABA
What is the excitatory neurotransmitter in the basal ganglia?
Glutamate
Which area in the basal ganglia is thought to be the ‘focal centre’ for the generation of tremors?
Globus pallidus
Which 2 areas of the brain, in theory, could be removed in order to treat tremors?
Thalamus
Globus pallidus
Name some motor effects of Parkinson’s disease
Bradykinesia
Resting tremor
Rigidity (lead pipe, cogwheel)
Name some other features of Parkinson’s (other than motor)
Festinating gait
Lack of facial expression
Micrographia
No weakness
Normal reflexes
What is the cause of Huntington’s disease?
Genetic
What motor effects are seen in Huntington’s?
Choreiform (jerky, involuntary movement)
Clumsy, unsteady gait
Difficulty with speech and swallowing
Name the 3 main groups of Parkinsonism
Pure Parkinsonism
- idiopathetic
- iatrogenic
- post-encephalitic
Parkinsonism with extras
- multiple systems atrophy
- progressive supranuclear palsy
Pseudoparkinsonism
- Wilson’s disease
- benign essential
- trauma and vascular related
What are the 4 cardinal symptoms of Parkinson’s?
TRAP:
Tremor (resting)
Rigidity (lead pipe, cogwheel)
Akinesia (bradykinesia)
Postural instability
Name 4 additional symptoms of Parkinson’s
Micrographia
Mask-like face
Sleep disturbances
Aprosodia
What % of substantia nigra is lost at the time of presentation of Parkinson’s disease?
Already 60% loss
Name the 4 dopamine pathways
Nigrostriatal
Mesolimbic
Mesocortical
Tubero-hypophyseal
Where does the nigrostriatal pathway go from/to?
Substantia nigra to striatum (putamen and caudate nucleus)
Where does the tubero-hypophyseal pathway go from/to?
What is its role?
Hypothalamus to pituitary
To inhibit prolactin
Which dopamine pathway is involved in Parkinson’s?
Nigrostriatal pathway
Where does the mesolimbic pathway go from/to?
Ventral tegmental area to limbic system
Where does the mesocortical pathway go from/to?
Ventral tegmental area to prefrontal cortex
What are the mesolimbic and mesocortical dopamine pathways involved in?
Emotions
Thoughts
Higher cortical processes
Which dopamine pathways are involved in psychosis?
Mesolimbic
Mesocortical
What is the main issue in treatment of Parkinson’s disease?
Dopamine does not cross the BBB
What is the precursor of dopamine?
Levodopa
What is the gold standard drug for Parkinson’s disease?
Levodopa
What needs to be considered when prescribing levodopa?
Nothing more can be done when maximum dose is reached.
Levodopa is metabolised quickly
Which enzyme breaks down L-dopa in the periphery?
Dopa-decarboxylase
Name a dopa-decarboxylase inhibitor
Carbidopa
What type of drug is carbidopa
Dopa-decarboxylase inhibitor
Which 2 enzymes break down dopamine in the CNS?
Catechol-O-methyltransferase (COMT)
Monoamineoxidase (MAOI-B)
Give an example of a catechol-O-methyltransferase inhibitor
Entacapone
What class of drugs does entacapone belong to?
Catechol-O-methyltransferase (COMT) inhibitor
Give an example of a monoamineoxidase (MAOI-B) inhibitor
Selgiline
What family of drugs does selegiline belong to?
Monoamineoxidase (MAOI-B) inhibitor
When are dopamine agonists used?
Useful in younger patients when you need to prolong treatment
Good first line treatment of Parkinson’s
Give an example of a dopamine agonist
Pramipexole
What class of drug is pramipexole?
Dopamine agonist
Which dopamine receptor do dopamine agonists primarily work on?
D2 receptors
What is a main side effect of dopamine agonists?
Which dopamine pathways do they act on to illicit these symptoms?
Psychiatric effects: hallucinations, visions etc.
Mesocortical
Mesolimbic
Name some side effects of dopamine based treatments
Sudden onset sleep
On-off effects
Drowsiness
Psychosis
Hypotension
Tachycardia
Nausea and vomiting
What drug is given to fill in the ‘on-off’ effects of Parkinson’s?
Apomorphine
Name the common side effect experienced with apomorphine
Nausea and vomitting
What drug is given prophylactically before apomorphine use?
Domperidone
When are anticholinergics useful in treating Parkinson’s?
Iatrogenic (drug-induced) Parkinson’s
Why are anticholinergics used to treat Parkinson’s?
Because a decrease in dopamine leads to an increase in acetylcholine concentration
Name an anticholinergic used to treat Parkinson’s
Orphenadrine
What class of drugs does Orphenadrine belong to?
Anticholinergics
What are the 3 forms of Wilson’s disease?
Dystonic
Pseudoparkinsonism
Cerebellar
What is Wilson’s disease?
Hepatolenticular degeneration caused by copper accumulation
What sign might you see in a patient with Wilson’s disease?
Kayser-Fleischer rings
What is the treatment for Wilson’s disease?
Copper chelators
Zinc - blocks copper absorption in the gut.
Define essential tremor
A familial progressive disorder characterised by intention tremor, not present at rest.
Rhythmic tremor 4-12Hz frequency
What 2 types of drugs treat essential tremors?
Give an example of a drug from each family
Beta- blockers
-Propanolol
Antiepileptic
-Primidone
Describe Huntington’s disease
Inherited neurodegenerative disorder
Autosomal dominant
What 4 types of drugs are used to treat Huntington’s disease?
Dopamine depleting drugs
Antipsychotics
Benzodiazepines
Antidepressants
Give 4 examples of drugs used to treat Huntington’s and their drug class
Tetrabenazine
-dopamine depleting
Risperidone, haloperidol
-antipsychotics
Diazepam
-benzodiazepine
SSRIS/TCAs
-antidepressants
Describe the mechanism of action of tetrabenazine
Dopamine-depleting drug
Blocks VMAT2 (vesicular monoamine transporter). prevents transport of dopamine into vesicles = less released in the synapse
Affects all monoamines, not just dopamine
Why does tetrabenazine cause depression?
Because it affects all vesicular monoamine transporters (e.g. 5HT and NA)
What 2 diseases are tics seen in?
Wilson’s
Huntington’s
What are the 3 treatments for tics?
Patient education
2nd generation antipsychotics
1st generation antipsychotics
What are the 2 main treatments for dystonia?
GABA agonists
-Baclofen
BDZ
-diazepam
What class of drug is baclofen?
GABA agonist
How do you treat chorea?
2nd generation antipsychotics
Dopamine depleting drugs (tetrabenazine)
GABAergic drugs (anti-epileptics, gabapentin, BDZ)
What is athetosis?
Slow, irregular, sinous writhing movements
What is ballismus?
large, violent, proximal, flinging movements of the limbs
If unilateral = hemiballismus
What causes ballismus?
Neurodegeneration of the subthalamic nuclei