Neurobiology of Disease 3 Flashcards
Out of neurodegerative and psychiatric illnesses, which one primarily features apoptosis or loss of neurones? (1)
Neurodegenerative
Out of neurodegerative and psychiatric illnesses, which one primarily features developmental defects? (1)
Psychiatric
Out of neurodegerative and psychiatric illnesses, which one shows changes in behaviour? (1)
Both can show changes in behaviour
Where is the pathology in upper motor neurone disorders? (1)
CNS or spinal cord
Give three examples of upper motor neurone disorders. (3)
- Stroke
- Multiple sclerosis
- ALS
Where is the pathology in lower motor neurone disorders? (1)
Outside the CNS
Give two examples of lower motor neurone disorders. (2)
Peripheral neuropathy
Myasthenia gravis
Where is the pathology usually situated in involuntary movement disorders? (1)
Basal ganglia
Give a common cerebellar pathology causing motor dysfunction. (1)
Tumour
Give three examples of involuntary movement disorders. (3)
- Parkinson’s disease
- Huntington’s disease
- Tremor
Is Parkinson’s disease neurodegenerative, developmental, or psychiatric? (1)
Neurodegenerative
At what age is Parkinson’s disease classed as early onset? (1)
40-60yrs
Is early onset Parkinson’s disease usually caused by…
a) genetic mutations
b) environmental factors
a) genetic mutations
Is early onset or late onset PD more prevalent? (1)
Late onset
At what age is Parkinson’s disease classed as late onset? (1)
> 85yrs
Is late onset PD usually caused by…
a) genetic mutations
b) environmental factors
Combination of both
Is PD more common in males or females? (1)
Males
(3:2 ratio)
Give five motor symptoms of Parkinson’s disease. (5)
- Slow movement (bradykinesia)
- Postural abnormalities (eg. rigid posture)
- Lack or rigidity of movement (akinesia)
- Mask-like expression
- Resting tremor
Give two psychological/cognitive symptoms of PD often seen in later stages. (2)
- Depression
- Dementia
Why is endocrine dysfunction often seen in Parkinson’s disease? (1)
Due to changes in the dopaminergic tuberoinfundibular pathway
Briefly describe the pathophysiology of Parkinson’s disease. (1)
Neurodegeneration of the extrapyramidal system (including the basal ganglia) due to loss of dopaminergic neurones in the substantia nigra.
Give three cellular mechanisms by which dopaminergic neurones in the substantia nigra may die in Parkinson’s disease. (3)
- Oxidative stress
- Mitochondrial dysfunction
- Proteosome dysfunction
Name the dopaminergic pathway which is disrupted in Parkinson’s disease. (1)
Nigrostriatal pathway
Complete the sentence relating to Parkinson’s disease. (2)
In PD, there is loss of ………………. neurones of the substantia nigra, resulting in less DA input to the ……………. of the basal ganglia.
dopaminergic
(dorsal) striatum
Describe the changes seen in brain slices of PD patients. (1)
Loss of pigmented neurones in substantia nigra pars compacta.
Name the pigment which normally makes the substantia nigra appear dark. (1)
Neuromelanin
Apart from the substantia nigra, name another brain area where large quantities of neuromelanin are found. (1)
Locus coeruleus
Briefly describe 5 neurotransmitter changes seen in Parkinson’s disease. (5)
Relate these to the brain areas where they are seen.
- Reduced DA in striatum
- Reduced DA in mesolimbic areas
- Reduced hypothalamic amines
- Reduced cortical noradrenaline and ACh
- Reduced neuropeptides (substance P) in striatum (and maybe also spinal neurones and interneurones)
What percentage reduction in dopaminergic neurotransmission to the striatum is required before motor symptoms are seen? (1)
60-70%
What effects are seen in Parkinson’s disease due to loss of dopamine in mesolimbic areas? (1)
Mood changes
What effects are seen in Parkinson’s disease due to loss of hypothalamic amines? (1)
Endocrine dysfunction
What effects are seen in Parkinson’s disease due to reduced cortical noradrenaline and ACh? (1)
Reduced cognition
What effects are seen in Parkinson’s disease which may be due to reduced neuropeptides in the striatum? (1)
Motor symptoms
Name a protein which is implicated in Parkinson’s disease. (1)
alpha-synuclein
Are a-synuclein aggregates causal or consequential of Parkinson’s disease? (1)
It is currently unknown
Describe the three components of the a-synuclein protein. (3)
- N-terminal
- Hydrophobic NAC region
- Acidic C-terminal
What is the function of the N-terminal of the a-synuclein protein? (1)
Interacts with membrane lipids
What is the function of the hydrophobic NAC region of the a-synuclein protein? (1)
Relevant for aggregation
What is the function of the acidic C-terminal of the a-synuclein protein? (1)
Involved in calcium binding
Very briefly describe (4 words) the normal role of the a-synuclein protein in cells. (1)
Synaptic function and exocytosis
Briefly describe the cascade of a-synuclein forming cytotoxic aggregates in cells. (6)
- Monomers (membrane-bound or free; can also be dimeric or tetrameric)
- Misfolding and/or hyperphosphorylation
- Oligomer
- Protofibrils
- Fibrils
- Lewy body
What is the structure called when the a-synuclein proteins aggregate? (1)
Lewy bodies
Very briefly, how do lewy bodies cause cell death? (2)
- They are cytotoxic
- They are unable to perform their normal functions
As well as motor dysfunction, what other aspect of PD might Lewy bodies contribute to? (1)
Dementia
Describe five normal, physiological roles of the alpha-synuclein protein in dopaminergic terminals at rest. (5)
- Inhibits DA synthesis (decreases TH phosphorylation)
- Aids in sequestration of cytosolic DA (increases amount of VMAT on vesicles)
- Prevents NT release through interactions with synaptic vesicles and SNARE proteins (prevents trafficking and docking)
- Facilitates recycling of synaptic vesicles by mediating membrane bending during endocytosis
- Maintains number of vesicles
Describe three normal, physiological roles of the alpha-synuclein protein in dopaminergic terminals during an action potential. (3)
- Following Ca influx, a-synuclein rapidly disperses from terminal
- Unimpeded vesicular trafficking and exocytosis
- Disinhibited TH and AADC, so DA can be replenished
Why does influx of calcium during an action potential cause alpha-synuclein to disengage from the membrane and disperse? (1)
Because alpha-synuclein interacts with the membrane in a calcium dependent manner.
Describe the effects that the loss of a-synuclein function has on dopaminergic axon terminals in Parkinson’s disease. (5)
- Increased DA synthesis (disinhibited TH and AADC)
- Decrease in VMAT levels
- Unregulated trafficking of synaptic vesicles
- Impaired endocytic vesicular recycling
- Decrease in size of vesicular pool
Describe how the distribution of dopamine in axon terminals is altered due to a-synuclein dysfunction in Parkinson’s disease. (2)
Increased cytosolic DA
with a reduction in DA in synaptic vesicles.
How does the increased cytosolic DA seen in Parkinson’s disease cause cell death? (3)
- DA auto-oxidises
- To produce reactive oxygen species
- And DA quinones
What would be the result of using miRNA to silence a-synuclein in neurones? (1)
Neurodegeneration
What does colocalisation suggest about the relationship between alpha-synuclein and glutamate in Parkinson’s disease? (1)
They are colocalised, suggesting that a-synuclein may be involved in glutamatergic neurotransmission, and therefore in PD, a-synuclein may alter glutamatergic function as well as DA function.
At the Drosophila NMJ, glutamate acts as the excitatory neurotransmission.
What is the effect of overexpressing a-synuclein at the Drosophila NMJ? (1)
What does this suggest about a-synuclein and how it affects glutamatergic function? (2)
Larger mEJP (miniature excitatory junctional potential)
Suggesting that a-synuclein may help to package glutamate into vesicles
Because overexpression results in more glutamate per vesicle
Briefly describe the proposed effects of a-synuclein on dopaminergic and glutamatergic activity. (2)
Hypodopaminergic activity
Hyperglutamatergic activity
The effects of a-synuclein on glutamate in Parkinson’s disease may be complicated.
Give two ways by which a-synuclein is proposed to increase glutamatergic neurotransmission. (2)
- Increase glutamate release from astrocytes
- Excessive activation of NMDARs on postsynaptic neurones
How could Parkinson’s disease be diagnosed using PET/SPECT imaging? (3)
- Use radioligand (CIT, cocaine analogue)
- Binds to presynaptic DAT
- Will see reduced signal
Explain why, during PET/SPECT imaging for Parkinson’s disease, using a DAT ligand would show a reduced signal but using a D2 ligand would not. (2)
Reduced DAT due to loss of dopaminergic neurones
however D2 found on postsynaptic neurones, which remain relatively unchanged.
What percentage of patients with PD have a first degree relative with PD? (1)
15%
Familial early onset Parkinson’s disease accounts for what percentage of PD cases? (1)
10-20%
Name five loci/genes which may be a risk factor for Parkinson’s disease. (5)
PARK1
PARK2
PARK4
PARK6
PARK7
Mutations in the PARK1 gene may play a role in Parkinson’s disease.
What protein does this gene encode? (1)
SNCA (a-synuclein)
Mutations in the PARK1 gene may play a role in Parkinson’s disease.
What phenotype is typically seen with mutations in this gene? (3)
Early onset PD
with Lewy bodies
and marked rigidity
Mutations in the PARK1 gene may play a role in Parkinson’s disease.
Give five mutations in this gene which confer risk for PD. (5)
A53T
A30P
E46K
H50Q
G15D
Mutations in the PARK1 gene may play a role in Parkinson’s disease.
PARK1 encodes the protein alpha-synuclein.
Name another loci/gene which encodes alpha-synuclein which may confer risk of PD. (1)
PARK4
PARK1 and PARK4 genes both encode a-synuclein and confer risk of PD.
What is the difference between the PARK4 and PARK1 genes? (2)
Different alleles
PARK4 is a triplication of the gene
Mutations in the PARK2 gene may play a role in Parkinson’s disease.
What protein is encoded by PARK2? (1)
Parkin
Mutations in the PARK1 gene may play a role in Parkinson’s disease.
What is the inheritance pattern of PARK1 mutations in PD? (1)
Autosomal dominant
Mutations in the PARK2 gene may play a role in Parkinson’s disease.
PARK2 encodes Parkin protein.
What is the role of the Parkin protein? (4)
Part of a ubiquitin proteasome
And acts as a protease
to regulate mitochondrial quality
through mitophagy and mitochondrial biogenesis.
Mutations in the PARK2 gene may play a role in Parkinson’s disease.
What is the inheritance pattern of PARK2 mutations in PD? (1)
Autosomal recessive
Mutations in the PARK2 gene may play a role in Parkinson’s disease.
Describe the PD phenotype seen in patients with PARK2 mutations. (3)
Early onset PD
restricted to SN cell loss
without Lewy bodies
Mutations in the PARK6 gene may play a role in Parkinson’s disease.
Which protein is encoded by PARK6? (1)
PINK-1
(PTEN-induced kinase-1)
Mutations in the PARK6 gene may play a role in Parkinson’s disease.
What is the inheritance pattern of PARK6 in PD? (1)
Autosomal recessive
Mutations in the PARK6 gene may play a role in Parkinson’s disease.
PARK6 encodes PINK-1 protein.
What is the role of PINK-1 protein? (3)
Mitochondrial serine/threonine protein-kinase
which recruits parkin to depolarised mitochondria
for mitophagy
Mutations in the PARK7 gene may play a role in Parkinson’s disease.
What protein does PARK7 encode? (1)
DJ-1
Mutations in the PARK7 gene may play a role in Parkinson’s disease.
What is the inheritance pattern of the PARK7 mutation in PD? (1)
Autosomal recessive
Mutations in the PARK7 gene may play a role in Parkinson’s disease.
PARK7 encodes the DJ-1 protein.
What is the role of this protein? (2)
Involved in oxidative stress response
and mitochondrial function.
Give two genes which increase risk of sporadic Parkinsonism. (2)
Leucine-rich repeat kinase 2 (LRRK2)
SNCA
True or false? Explain your answer if necessary. (1)
Sporadic Parkinsonism tends to occur without family history or gene mutations.
False -
It does tend to occur without family history
However can occur due to multiple gene alterations with influence risk factor susceptibility to PD
Give two environmental risk factors for Parkinson’s disease. (2)
- MPTP (drug-induced neurodegeneration)
- Paraquat/rotenone (exposure to herbicide)
Describe how MPTP may cause PD. (4)
- Converted to MPP
- By monoamine oxidase B in astrocytes
- Taken up into DA neurones by DAT
- Acts as a mitochondrial toxin
Briefly describe how herbicides can cause PD. (2)
- Taken up by DA neurones via DAT (or diffuse across membrane)
- Cause oxidative stress
Complete the passage relating to PD risk factors. (3)
Genetic factors are thought to primarily affect ……………… and ………………….. function.
However environmental factors predominantly affect …………………… function.
synaptic
mitochondrial
mitochondrial
Name a type of therapeutic drug which causes Parkinsonism. (1)
Antipsychotics/neuroleptics
Name a potential target for treatment in Parkinson’s disease. (1)
Postsynaptic DA receptors
Why can’t dopamine be used to treat PD? (1)
Cannot cross BBB
Why can’t L-DOPA be used alone to treat Parkinson’s disease? (1)
It would be converted to dopamine in the periphery, and dopamine cannot cross the BBB.
What is the most common treatment for Parkinson’s disease? (1)
Levodopa (a dopamine precursor)
+
Carbidopa (peripheral DOPA decarboxylase inhibitor)
Describe how levodopa + carbidopa is effective in PD. (4)
Carbidopa inhibits DOPA decarboxylase outside CNS
Levodopa crosses BBB
Converted to dopamine in decarboxylase-positive neurones
So increased DA neurotransmission in the CNS
In addition to not being able to cross the BBB and act in the CNS, give another reason why dopamine should not be applied systemically. (1)
It can be converted to noradrenaline/adrenaline and act systemically.
Give five unwanted side effects of long-term levodopa+carbidopa use in PD. (5)
- Chorea and involuntary movements
- Rapid fluctuation of clinical states (on-off effect)
- Nausea and anorexia
- Hypotension
- Psychotic effects
When does development of chorea and involuntary movements usually occur in PD treatment? (1)
After about 2yrs of use
Why are nausea and anorexia often seen in PD treatment? (1)
Due to peripheral drug effects
Why are psychotic effects often seen as a side-effect of PD treatment? (1)
Due to changes in the mesocortical/mesolimbic pathways pathways
In order of earliest effects to later effects, describe how the efficacy of levodopa/carbidopa therapy changes over time in PD. (5)
- Excellent control
- End of dose ‘wearing off’
- Fluctuations (on-off effect)
- Dyskinesias
- Loss of control
How long after diagnosis of PD is death likely to occur? (1)
10-15yrs
Suggest 6 alternative therapeutic strategies (apart from levodopa) in PD treatment. (6)
- D2 receptor agonists
- Monoamine oxidase B inhibitors
- Catechol-O-methyl transferase inhibitors
- Increase DA release from nerve terminals
- Adenosine A2a receptor antagonist
- Muscarinic receptor antagonists
In which subset of PD patients are D2 receptor agonists more likely to be used? (1)
Early onset
Give two examples of D2 receptor agonists which can be used to treat PD. (2)
- Ropinirole
- Bromocriptine
Give an example of a MAOB inhibitor that can be used to treat PD. (1)
Selegiline
Give a condition that must be met for COMT inhibitors to be effective in PD treatment. (1)
Must be used with L-DOPA
Give two examples of COMT inhibitors that can be used to treat PD. (2)
- Tolcapone
- Entacapone
Which receptor/receptors do D2 receptor agonists bind to in order to treat PD? (1)
D2
D3
D4
When are adenosine A2a antagonists used to treat PD? (1)
As add-on therapy with L-DOPA
Give a medication that treats PD by increasing DA release from nerve terminals. (1)
By what mechanism does this drug work? (1)
Amantadine
Mechanism not really known
What specific symptom of Parkinson’s disease may be helped by muscarinic receptor antagonists? (1)
Tremor
Apart from drugs, give three other techniques that may potentially be used to treat Parkinson’s disease. (3)
- Stem cell transplant
- Promotion of neuronal survival and reinnervation
- Blockade of a-synuclein aggregation
How might neuronal survival and reinnervation be promoted in PD treatment? (1)
Nicotinic receptor agonists
Name the brain pathway which seems to be most involved in addiction and reward. (1)
Mesolimbic dopamine pathway
In addition to dopaminergic neurotransmission, name another type of neurotransmission which innervates the nucleus accumbens. (1)
Serotonergic
Briefly describe an experimental setup to test the activity of VTA neurones in reward and reward prediction. (4)
HINT: This is done in mice/rats
- Rodent in box with lever to deliver reward
- Lever press delivers IV cocaine
- Microelectrodes able to record VTA activity
- Can manipulate size of reward (ie. amount of cocaine) to test reward prediction error
In a rodent test where rewards are self-administered and VTA neuronal activity is recorded, describe what you would expect to see and what the effects of this are if the reward is unpredicted. (3)
- Phasic, short-lasting burst of activity in VTA neurones
- This results in DA release from nerve terminals
- In the nucleus accumbens and frontal cortex
In a rodent test where rewards are self-administered and VTA neuronal activity is recorded, describe what you would expect to see and what the effects of this are if the reward is better than predicted. (2)
What is this response called? (1)
Stronger neuronal response elicited
resulting in more DA release
Positive prediction error response
In a rodent test where rewards are self-administered and VTA neuronal activity is recorded, describe what you would expect to see and what the effects of this are if the reward is worse than predicted. (2)
What is this response called? (1)
Decrease in neuronal firing
Less DA release
Negative prediction error response
In a rodent test where rewards are self-administered and VTA neuronal activity is recorded, describe what you would expect to see and what the effects of this are if the reward is fully and accurately predicted. (2)
No response by the neurones
so no change in DA
How does the dopamine reward prediction error contribute to learning? (1)
The dopamine response to a reward (outcome) changes prediction for the future.
Describe how the dopaminergic response to reward and the reward prediction error may contribute to addiction. (4)
- Body doesn’t experience as strong a reward to drug as what is expected
- Perhaps due to tolerance
- Negative DA response (and negative feeling) will be elicited
- So person increases dose to try and increase DA response
Name a technique that can be used in rodents to measure ECF levels of neurotransmitter during activity. (1)
Microdialysis
Briefly describe how microdialysis would enable measurement of dopamine and serotonin levels in the brain in response to a reward (in rodents). (4)
- Probe implanted with semi-permeable membrane
- Perfused with artificial CSF
- NTs transfuse from brain parenchyma to inside the probe with aCSF
- Can analyse the dialysate and measure levels of NT
What is an advantage of using Drosophila to investigate reward and learning pathways instead of rodents or humans. (1)
There are less neurones present so they are easier to identify and map.
Briefly describe an experimental setup which would allow investigation of reward and learning pathways in Drosophila larvae. (4)
- Train larvae to associate specific smell with reward (eg. fructose food medium)
- Give non-rewarding food with a different smell
- In test, have both smells present and count how many larvae go towards the rewarding smell
- This can be done with genetic knockouts of specific receptors or pathways
Name the brain region in Drosophila where reward and learning are thought to interact with each other. (1)
What neurotransmitter is involved in this? (1)
Mushroom body
Dopamine
Give the three general targets/brain changes of drugs of abuse. (3)
- Increase DA in nucleus accumbens
- Enhance serotonergic function (potentially in nucleus accumbens)
- Block NMDA receptors
Give nine drugs of abuse which act by increasing dopamine in the nucleus accumbens. (9)
- Opiates/Opioids
- Nicotine
- Amphetamine
- Cocaine
- Ethanol
- Cannabis
- Cathinones (amphetamine-like)
- Barbiturates
- Caffeine
Give two drugs of abuse which may act by enhancing serotonergic function (potentially in nucleus accumbens). (2)
- LSD
- Ecstasy (MDMA)
Give two drugs of abuse which may act by blocking NMDA receptors. (2)
- Phencyclidine (PCP)
- Ketamine
Drugs of abuse which act by blocking NMDA receptors produce what effects? (2)
- Hallucinations
- Delusions
How does cocaine enhance dopaminergic neurotransmission? (2)
Indirect agonist at dopamine receptors
by inhibiting dopamine reuptake transporters
How do amphetamines and amphetamine-related drugs of abuse enhance dopaminergic neurotransmission? (2)
Indirect agonist at dopamine receptors
by stimulating dopamine release
Complete the passage relating to drugs of abuse. (2)
In general, drugs of abuse tend to increase dopamine levels, predominantly in the ………………………… brain region, and in a ……………………..-dependent manner.
nucleus accumbens
dose
Complete the passage relating to dopamine and drugs of abuse. (2)
The faster, higher, and more reliable the elevation in brain dopamine levels, the ………………… the reward (euphoria), and the ……………… likely it is for addiction to occur.
greater
more
Give two properties of drugs of abuse which can affect the speed, level, and reliability of the dopamine elevation in the brain. (2)
- Concentration of drug
- Formulation and absorption rate of drug
What is physical drug dependence and how does it relate to addiction? (1)
Physical drug dependence is an altered physiological state produced by repeated drug administration.
Dependence can often precede addiction.
Give four properties of a drug which can affect the physical dependence on it. (4)
- Pharmacokinetics
- Structure
- Pathways
- Receptor affinity
Give four examples of drugs of abuse with very strong physical dependence. (4)
- Morphine
- Heroin
- Cocaine
- Nicotine
Give four examples of drugs of abuse with very weak or absent physical dependence. (4)
- Cannabis
- Caffeine
- Ecstasy (MDMA)
- LSD
Describe how GABAergic, glutamatergic, and dopaminergic neurones interact with each other to affect DA transmission from VTA to nucleus accumbens. (1)
GABAergic neurones usually inhibit VTA neurones
Glutamatergic input usually stimulates VTA neurones
Give four effects of ethanol on GABAergic, glutamatergic, and dopaminergic neurones in the VTA/nucleus accumbens to increase dopaminergic neurotransmission. (4)
- Directly increases firing rate of VTA neurones
- Increases Ih and GIRK currents in VTA DA neurones to cause depolarisation
- Decreases GABAergic inhibition of VTA neurones
- Enhances glutamatergic synaptic strength (increased AMPA/NMDA ratio)
Give three effects of nicotine on GABAergic, glutamatergic, and dopaminergic neurones in the VTA/nucleus accumbens to increase dopaminergic neurotransmission. (3)
- Directly increases VTA cell firing
- Increased excitatory glutamate release
- HOWEVER also increases inhibition by GABAergic interneurones
(but there is an overall increase in DA)
Give four drugs of abuse which directly increase DA concentration either at the synapse or by acting directly on VTA neurones. (4)
- Cocaine
- Ethanol
- Nicotine
- Amphetamine
Describe two effects (one in more detail than the other) of morphine on GABAergic, glutamatergic, and dopaminergic neurones in the VTA/nucleus accumbens to increase dopaminergic neurotransmission. (3)
- Activates MORs on GABAergic interneurones
- Which results in a decrease in GABAergic cell firing and IPSP frequency
- Also enhances glutamatergic synaptic strength (increased AMPA/NMDA)
As well as cocaine acting directly at the synapse to increase DA, give an effect that it may have in the VTA on either dopaminergic, glutamatergic, or GABAergic neurones. (1)
Enhances glutamatergic synaptic strength (increases AMPA/NMDA ratio)
Cannabinoids result in increased DA release in the nucleus accumbens.
Are cannabinoids thought to act directly on dopaminergic neurones in the VTA, or indirectly on GABAergic or glutamatergic neurones in the VTA to enhance dopamine? (1)
Indirect
Describe the mechanism of how alcohol is able to enhance DA release from the VTA by decreasing GABAergic interneurone inhibition. (4)
- Alcohol causes beta-endorphin release
- Endorphins act on MORs of GABAergic interneurones
- This results in the neurone being inhibited and less GABA release
- So less inhibition of VTA neurones and more DA release
Why is it important clinically to understand the pathway and cellular mechanism of how alcohol causes increased DA? (1)
Understanding this mechanism may allow new pharmacological approaches to treating alcohol addiction.
How does the long-term use of drugs of abuse lead to long-term addiction? (4)
Alter gene expression
Due to dopamine binding to GPCRs
Affecting transcription factors and/or epigenetics
Which can then cause altered synaptic plasticity and attenuated reward to normal stimuli
What is the difference between opiates and opioids? (2)
Opiates are natural substances
Opioids are man-made, synthetic forms
Give four examples of opiates. (4)
Morphine
Heroin
Opium
Codeine
Give two examples of opioids. (2)
Methadone
Fentanyl
Complete the passage relating to opiates and opioids. (5)
Opiates and opioids are ……………….. at receptors (for example the u-opioid receptor, MOR).
These receptors are ………………………….
They act to ………………… neurotransmitter release.
They may do this by enhancing …………. channels and inhibiting ……………. channels.
HINTS:
1 is agonists/antagonists
2 is ligand-gated ion channels / GPCRs
3 is increase/reduce
4 and 5 are types of channels
agonists
GPCRs
reduce
K
Ca
Give six acute effects of opiates/opioids. (6)
*This includes therapeutic, drugs of abuse, and side effects
- Analgesia
- Euphoria
- Positive reinforcement
- Tranquillity
- Miosis (pupillary constriction)
- Respiratory depression
Give six chronic effects of opiates/opioids. (6)
- Constipation
- Depression
- Insomnia
- Dependence
- Anhedonia
- Tolerance
Give five withdrawal effects of opiates/opioids. (5)
- Craving
- Restlessness
- Insomnia
- Diarrhoea
- Cold flashes with goosebumps (‘cold turkey’)
Describe the time course of opiate/opioid withdrawal symptoms. (2)
- When do symptoms peak?
- When do symptoms tend to subside?
Peak 24-72hrs after last dose
Subside after about a week
What G protein is usually linked to opioid receptors? (1)
Gi
Complete the sentence relating to cocaine. (2)
Cocaine is an …………. extracted from the ………………. (Erythroxylum coca).
Alkaloid
coca tree
Give three formulations in which cocaine can be taken. (3)
- Leaves chewed (in Peru)
- Snorted
- Smoked with tobacco
In Peru, people chew cocaine leaves. What molecular form of cocaine does this produce? (1)
Cocaine hydrochloride
Complete the sentence relating to cocaine. (4)
Crack cocaine is a form of cocaine known as a ……………………
Crack cocaine results in ……………….. tolerance, ………………… physical dependence, and ………………… psychological dependence.
Free base
Little
Little
Strong and rapid
Give three effects of low dose cocaine. (3)
Euphoria
Excitement
Increased capacity for work
As well as increasing dopamine, what other effects on neurotransmission can cocaine have at high doses? (2)
Blocks NA and adrenaline uptake
to cause overactivity of the sympathetic nervous system.
Give four autonomic symptoms that can be caused by high dose cocaine. (4)
Hypertension
Tachycardia
Dilated pupils
Palpitations
What is meant by ‘tolerance’? (1)
Higher doses required to maintain the same effect.
Ki is the amount of a drug needed to inhibit a protein by a certain amount.
What would you expect to see if you compared the Ki for cocaine inhibiting DAT between people who regularly take cocaine, and people who have never taken cocaine? (1)
Explain what this means. (1)
Ki higher for people who regularly take cocaine
More cocaine needed for same DAT inhibition and DA increase in people who regularly take cocaine.
Describe what you would expect to see in an experiment where:
the same dose of cocaine is given to a group of people who have never taken cocaine before and a group who regularly use cocaine, in terms of dopamine levels. (1)
What method of measuring DA levels would be used if this experiment was carried out in rodents? (1)
Larger rise in dopamine in cocaine-naive group
Microdialysis
Complete the sentence relating to cannabis. (2)
Cannabis, or marijuana, refers to the various preparations of the ……………………….. plant, with ………………. as the active ingredient.
Cannabis sativa
THC (tetrahydro-cannabinol)
The drug of abuse, cannabis, mimics the effects of endogenous endocannabinoids.
Give an example of an endogenous endocannabinoid. (1)
Anandamine
Very briefly describe the mechanism of how cannabis works when used as a drug of abuse. (1)
Inhibits a wide range of neurotransmitters from being released in the brain and periphery.
What types of receptors (ligand-gated ion channels or GPCRs) are cannabinoid receptors? (1)
GPCRs
What G protein is coupled to cannabinoid receptors? (1)
Gi
Name two types of cannabinoid receptors and describe their distributions in the body. (4)
CB1
CB2
CB1 found in CNS
CB2 largely peripheral
What is the effect seen with a moderate dose of cannabis? (1)
Mild euphoric effect
What is the effect usually seen with a high dose of cannabis? (1)
Dysphoric effect (particularly in naive users)
True or false? Explain your answer if appropriate. (1)
Cannabis has an analgesic effect.
True
How does cannabis stimulate appetite? (1)
It acts on feeding centres in the hypothalamus and possibly gut.
Cannabis has a very low acute toxicity.
Describe what is meant by this. (1)
Not really any long-term effects from just using it once or for a short time.
There are concerns about chronic heavy users of cannabis potentially developing what condition? (1)
Psychosis
Very briefly describe the mechanism by which high dose cannabis is thought to increase dopamine. (1)
Inhibition of GABAergic VTA interneurones
Anandamide, an endogenous endocannabinoid, is broken down by what enzyme? (1)
FAAH (fatty acid amide hydrolase)
What would be the effect on dopamine levels if an FAAH (fatty acid amide hydrolase) inhibitor was given? (1)
Explain your answer. (3)
Increased dopamine
Because FAAH usually breaks down cannabinoids
So if an inhibitor is given the cannabinoids persist for longer
And cannabinoids increase DA release
The endogenous endocannabinoid, anandamide, enhances DA release by acting on which receptor? (1)
CB1
Give the general chemical name of the structure of amphetamine drugs. (1)
Phenylethylamine
Give two examples of amphetamine drugs. (2)
- Methamphetamine
- Dexamphetamine
Give 12 effects of taking amphetamines (as drugs as abuse). (12)
- Increased wakefulness
- Increased concentration
- Decreased fatigue
- Decreased appetite
- Enhanced performance (eg. sport/war)
- Euphoria
- Increased self-esteem
- Increased self-confidence
- Aggression
- Excessive feelings of power
- Obsession
- Paranoia
Give five side effects of amphetamine drugs. (5)
- Some degree of tolerance
- Psychosis (with chronic use and/or high doses)
- Increased cardiovascular tone
- Raised blood pressure
- Tachycardia
Amphetamines increase synaptic levels of DA, NA, and 5HT.
Briefly explain two mechanisms as to how this happens. (2)
- Releases monoamines from neuronal storage vesicles
- Block DAT, NET, and SERT transporters
True or false? Explain your answer if appropriate. (1)
Different isoforms of amphetamine (which all act via the same mechanism) all cause the same response profile (dose-response curve).
False - different isoforms cause different response profiles
Which form of the drug amphetamine, is neurotoxic and can kill midbrain dopamine neurones? (1)
Methamphetamine
PET scans using a ligand for the DAT transporter can be carried out in people who abuse drugs and in control groups.
What would you expect to see in people who abuse amphetamines regarding the DAT ligand binding in a PET scan? (2)
Decreased signal given off
due to decreased DAT levels.
Ki is the concentration of a drug needed for 50% inhibition of a protein.
What is the relationship between Ki and affinity? (1)
Lower Ki means higher affinity
Looking at the Ki of cocaine for NET, DAT, and SERT; which value would you expect to be the lowest? (1)
DAT
Looking at the Ki of amphetamine for NET, DAT, and SERT; which value would you expect to be the lowest? (1)
NET
What is the relationship between IC50 and drug binding affinity? (1)
Lower IC50 means higher affinity
DAT/SERT binding ratio for a drug can be calculated from the IC50 values.
This can be used to predict potential for abuse.
Describe in words what is meant by the DAT/SERT ratio (giving an example of what a high or low ratio means). (1)
What is the relationship between DAT/SERT ratio and potential for drug abuse? (1)
Lower ratio means the drug binds more to SERT and inhibits SERT more than DAT.
Lower ratio = lower abuse potential
The DAT/SERT ratio can be calculated for MDMA, amphetamine, and cocaine.
What do you expect the relative DAT/SERT ratios to be for these compounds, and which drugs have more potential for abuse? (2)
DAT/SERT ratios:
MDMA<cocaine<amphetamine
Potential for abuse:
MDMA<cocaine<amphetamine
