Week 11 - Biology of addictions Flashcards
Are dopamine and GABA excitatory or inhibitory neurotransmitters?
GABA is inhibitory
Dopamine can function as either excitatory or inhibitory, depending on what type of receptor it binds to
The mesolimbic and mesocortical pathways are important in controlling what type of behaviour?
Motivated behaviour
What are the three routes of injection?
- subcutaneous
- intramuscular
- intravenous
The quicker a drug reaches the brain, the ……. ?
Greater its potential for inducing euphoria
The way the body metabolises or excretes drugs may have impacts on what?
Their rewarding and addictive properties
If someone is not able to fully metabolise alcohol (due to a genetic variant), what is the toxic chemical which starts to accumulate in the body?
Acetaldehyde
How does methylphenidate alter dopamine neurotransmission?
It blocks the dopamine transporter, preventing reuptake, meaning that dopamine stays in the synapse longer which increases its chance of binding to receptors
Which type of receptors is nicotine thought to bind to?
Cholinergic receptors
What, in the brain, does nicotine mimic the effect of?
Acetylcholine
When nicotine mimics the effect of acetylcholine, what is the resulting effect?
It triggers an action potential in the dopaminergic neuron, which causes the release of dopamine
Does nicotine act as an agonist or antagonist at cholinergic receptors?
Agonist
What is the name of the receptors which heroin binds to?
mu-type opiod receptors
What do mu-type opiod receptors usually do?
Mediate the effects of the endogenous opiods known as enkephalins and endorphins
If the GABAergic neuron is not firing, what is not happening?
The dopaminergic neuron is not being inhibited
Is heroin an agonist or antagonist?
Agonist
Acetylcholine binding to cholinergic receptors on the dopaminergic neuron can have what effect on the dopaminergic neuron?
Excitatory
What is the resulting effect of acetylcholine bounding to cholinergic receptors on dopaminergic neurons?
Dopaminergic neurons are excited, which causes dopamine to be released in the nucleus accumbens and prefrontal cortex
The GABAergic inhibition of the dopaminergic neuron can block what effect?
Dopamine being released into the nucleus accumbens and prefrontal cortex
What does heroin bind to?
mu-type opiod receptors on a GABAergic neuron
What is prevented from being released if heroin binds to mu-type opiod receptors on a GABAergic neuron?
It prevents the GABAergic neuron from releasign GABA
If there is less binding of GABA to receptors on the dopaminergic neuron, what does that mean?
That the dopaminergic neuron will be more easily activated and and excited when acetylcholine binds to cholinergic receptors
Which neurotransmitter is thought to play a role in the propensity to gamble?
Dopamine
What is the current primary method for measuring molecules in the conscious human brain?
Through positron emission tomography (PET) scans
Which two areas of the brain generally have high density of dopamine receptors?
- Nucleus accumbens
- Prefrontal cortex
Why can biological results from a PET scan be challenging to interpret?
As the drug user is not being observed in their usual drug-taking location
What is the name of the technique which is used in order for us to be able to study animals in PET scanners?
Microdialysis
How does microdialysis in animals work?
During it,a small probe is inserted into the animal’s brain and samples of extracellular fluid are taken during behaviour, which are later studied using specialist lab equipment
What is meant by the term transients?
Changes in dopamine neurotransmission
What is the name for a receptor which functions by way of mediating the flow of ions in or out of the neuron?
Ionotropic receptors
What are ionotropic receptors?
A type of receptors that are directly linked to a channel in the cell membrane which is how ions flow in or out the cell
Are ionotropic receptors slow or fast acting?
Fast acting, because they are linked directly to the ion channels
Receptors which do not work on an ionotropic basis are known as what?
Metabotropic receptors
What are metabotropic receptors?
A type of receptor that is linked to a set of reactions and signalling proteins within the cell
What is meant by the term subtypes?
It is the name for different receptors which can be for the same neurotransmitter
What are the two subtypes of dopaminergic receptors known as?
- D1
- D2
What is meant by the term metabotropic?
A type of membrane that initiates a number of metabolic steps to modulate cell activity
Where are D1 subtypes located?
On the postsynaptic membrane
Are D1 subtypes inhibitory or excitatory?
Excitatory
Are D2 receptors inhibitory or excitatory?
Inhibitory
Where can D2 receptors be found?
On either the pre- or postsynaptic membrane
What are the two types of receptors that the nervous sytem utilises?
- Ionotropic
- Metabotropic
Are dopaminergic receptors ionotropic or metabotropic?
Metabotropic
What are G proteins?
Proteins which either stimulate or inhibit a series of further proteins
When dopamine binds to a D1 receptor, is the protein called kinase A (PKA) stimulated or inhibited?
Activated
When dopamine binds to a D2 receptor, is the protein called kinase A (PKA) stimulated or inhibited?
Inhibited
Protein kinase A (PKA) is stimulated or inhibited by the D1 receptor?
Stimulated
Protein kinase A (PKA) is stimulated or inhibited by the D2 receptor?
Inhibited
What effect can PKA (protein kinase a) have on the cell membrane?
It can alter the shape and structure of the cell membrane
When PKA (protein kinase a) affects a cell membrane, what are the results of that change?
Ions may be able to flow more easily through the channel, or cause the channel to remain ‘open’ for longer
What are transcription factors?
A family of proteins that can bind to regulatory sites on a gene, thereby promoting transcription of DNA to mRNA
If PKA (protein kinase a) travels to the cell membrane, what can it activate?
Transcription factors
Activation of D1 receptors has what effect to PKA (protein kinase a)?
It activates it
If dopamine binds to D2 receptors, what effect does that have to PKA (protein kinase a)?
It inhibits it
When PKA (protein kinase a) is activated and travels into the cell nucleus, what is the name of the transcription factor which it activates?
CREB
What does the transcription factor known as CREB do?
It activates the transcription of a gene known as the FosB gene
What is the function of the FosB gene?
It produces a protein called deltaFosB
If D1 receptors are activated, leading to elevated levels of deltaFosB in neurons, what behaviour does this affect?
It is thought to control various aspects of addiction
What can the protein deltaFosB be an indicator or biomarker for?
Addiction
What is meant by the term sensitisation?
A state in which the same amount of reward causes a greater effect over timeq
What is incentive sensitation?
A theory regarding drug addiction that posits that the thing that drives people is the desire for the reward, rather than its pleasurable experience
What is one psychosocial factor which can have an impact on (and enhance) incentive sensitisation?
Stressful experiences
Since stress can enhance incentive sensitisation, how would you predict impact it to impact deltaFosB production?
Repeated exposure to stressful events increases deltaFosB production
What happens in a Skinner box?
Inside the box there is a lever, next to a tray that food pellets are dispensed into. It is designed to see if an animal learns the association between learning to press the lever to gain food
What is behavioural economics?
The psychological study of decision-making from an economical perspective
What is an example of behavioural economics in human behaviour?
Someone who has never used heroin may be much less likely than a regular user to pay a large sum of money for heroin
If a rat were to be pressing a lever in order to obtain a reward, would that be an example of operant conditioning or Pavlovian (classical) conditioning?
Operant conditioning because the rat is performing an action instrumental in receiving a reward
What is meant by the term classical conditioning?
Association between an involuntary response and a stimulus
What is meant by the term operant conditioning?
Association between a voluntary behaviour and a consequence
If there are stimuli present which in an environment which do not pair with an unconditional stimulus, how do we refer to them?
As a CS minus (CS-)
Why is it important to consider the impact of Pavlovian (classical) conditioning on addictive behaviours?
The development of addiction does not occur in isolation
If there are stimuli present which in an environment which do pair with an unconditional stimulus, how do we refer to them?
A conditioned stimulus (CS+), or reward-paired cue
What inadvertant effect may occur if there are stimuli present which are not immediately associated with an addiction?
They may become a conditioned stimulus (CS+)
Cues which aquire the potential to drive behaviour and induce relapse are referred to how?
Motivational magnets or incentive stimuli
What is meant by the term incentive stimuli?
Cues that can evoke an emotional state such that they have the potential to drive behaviour
What term is used to describe stimuli that evoke motivational states?
Incentive stimuli
What is an example of a potential CS+ in the context of addiction to nicotine?
If someone smokes in a social setting they may start to feel the need for a cigarette each time they are in that situation
Pavlovian conditioning elicits which type of response?
A conditioned response
What does the abbreviation ‘CS+’ mean?
Conditioned stimulus (positive)
What is meant by the term goal tracker?
An individual who interacts mainly with aspects of reward delivery
What is meant by the term sign tracker?
An individual who interacts mainly with the cues relating to a reward
Are sign trackers or goal trackers more likely to exhibit addiction-related behaviours?
Sign trackers
When initially receiving a reward, dopamine releasing neurons in which area of the brain become active?
The ventral tegmental area
After repeatedly being exposed to a reward, dopamine is released from which area of the brain?
The nucleus accumbens
The cue-associated dopamine release which occurs when dopamine is elicited from the NAc rather than the VTA acts as a signal to do what?
Pursue reward
After repeated exposure to a reward, the dopaminergic neuron no longer responds to the reward itself. This is demonstration of what kind of learning?
Reward-related learning
The shift in the timing of release of dopamine from reward to reward prediction is thought to be a biological mechanism of what?
Addiction
What is thought to be one biological mechanism of addiction?
The shift in the timing of release of dopamine from reward to reward prediction
