Addiction Flashcards
How much can addiction cost per year?
9 Billion
Outline what addiction is
- Addiction is a treatable brain disorder or disease which causes dysfunctional decision making, loss of control of taking a drug and continued seeking behaviour
- Not all those that take drugs become addicted
- It has underlying genetic, neural, developmental, environmental and social causes
- Where an individual uses substances or engages in behaviours that become compulsive and often continue despite harmful consequences
What are two reasons people take drugs?
- To enduce positive feeling
- To self-medicate and feel better
- May be an accumulation of these factors
What are the 3 biggest questions in addiction?
- What determines vulnerability compared to resilience to develop a SUD
- How can research address these issues?
- How do we look at comorbidity with otehr mental health conditions?
How many criteria in the DSM5 is needed for a mild disoder?
2
How many criteria in the DSM5 is needed for a moderate disoder?
6
How many criteria in the DSM5 is needed for a severe disoder?
7-11
What are the 11 DSM5 addiction criteria?
- Taking more drug than intended
- Unsuccessful efforts to cut down
- Strong urges and cravings for the drug (cues)
- Excessive time spent acquiring the drug
- Activities given up due to use of drug
- Failure to fulfil major role obligations
- Use despite negative effects
- Recurrent use in hazardous situations
- Continued use despite consistent social or interpersonal problems
- Tolerance to drug effect
- Withdrawal signs
What are the 5 mos addictive substances?
- Heroin (1 in 4 who try it become addicted)
- Alcohol (death rate of over 3 mill a year
- Cocaine (bill dollar industry- 21% who try may become addicted)
- Barbiturates
5 Nicotine
How does the dopamine reward pathway work?
Mesolimbic system
- VTA projects to NA (part of the striatum)
- Dopiminergic neurons project to and determinate in the NA
- NA binds to D1 and D2 receptors on the MSN which are GABAergic
- Influences these neruons which projects to other areas of the basal ganglia, PFC, amygdala and hippocampus
What is the addiction cycle?
- Initial use /experimentation/continued use/abuse (flooding of dopamine in NA)
- Tolerance/dependence (come down as the stress system becomes activated leading to…)
- Withdrawal/negative affect (depends on the drug and the amount we take)
- Addiction
- Craving/Impulsivity/compulsivity/preoccupation/anticipation. Anticipation of taking the drug again- Amygdala and hippocampus are activated
- Relapse (reward pathway brcomes tolerant- need more drug for th same effect)
What neuroadaptations occur with repeat drug exposure?
- Changes in receptor senstivity
- Changes in neurotransmitter release
- Changes in neural circuitary
How does tolerance occur?
The brian becomes less responsive and needs greater amounts to produce the same feeling
When does dependence develop?
Results in withdrawal symptoms if substance not taken (overarching driver within the cycle)
What leads to craving, stress and negative affect?
Dysregulation of dopamine system leading to increased reliance on substance for pleasure
What does relapse involve?
The reactivation of neural pathways involved in addiction and is triggered bby exposure to the substance, or cues/contexts associated with the substance
Outline the neurobiology of the addiction cycle
- Incentive salience- refers to what were neural stimuli becoming impaired with and attaching importance to specific stimuli
- Reward defecits and increased stress- Reward prediction with cues after repeated exposure shifts change in reward neurocircuitary in VTA, NA to substantia nigra, pars compacta and dorsolateral striatum
- Extends to the amygdala which receives input from the HPA Axis. Associated with negative reinforcement associated with withdrawal
- Exectuive function defecits- Craving controlled by the PFC which affects the ability ti make deicisions and organise activities. Cnages in the circuitary cannot apply brakes to behaviours. Anterior cingulate cortex constantly assesses value of stimuli and the orbitofrontal cortex- all impaired
Essentially what is the driving factor of neurobiology of addiction?
LTP and formation of drug-related memories
What is incentive salience related to?
- Positive reinforcement
- This is stronger when a drug releases a rapid and intense release of dopamine in the accumbens/striatum
What are the dopamine circuits dissociable roles with repeated exposure?
- Mesolimbic- gives motivational pull to cues and the rewards they predict
- Nigrostriatal- gives a push towards invigorative or arousing behaviours
How does the mesolimbic and the nigrostriatal system influence self-administration behaviours?
- Mesolimbic- drug reward, drug cue motivation, drug seeking renewal
- Nigrostriatal- escalated drug use and rigid drug seeking
How does the mesolimbic and the nigrostriatal system influence social interactions?
- Mesolimbi- social reward, affiliative behaviours, defeat-enhanced motivation
- Nigrostriatal- Social recognition, social withdrawal
How does the mesolimbic and the nigrostriatal system influence risky decision making?
- Mesolimbi- motivational conflice, loss sensitivity, impulsive choice
- Nigrostriatal- punishment ersistance, reward memory, feedback insensitivity
How is the PFC involved in addiction?
Is involved in decision making and inhibtory control and shows impairment in addiction
How is the amygdala involved in addiction?
Processes the emotional response, including those related to stress and craving
How is the hippocampus involved in addiction?
In forming and consolidation (drug related) memories that contribute to craving and stress
Outline synaptic plasticity in the addiction cycle
- Tonic to phasic firing of dopamine neurons LTP in VTA and NA medium spiny neurons of the direct pathway (D1 receptors)
- Can cause long term depression in the medium spiny neurons of the indirect pathway (D2 receptors)
What does LTD in NAcc lead to?
- Increased trafficking of AMPA receptors
- Increased cAMP production
- Increased CREB phosphorylation
- Reduction in the sensitivity of the reward pathway and dopamine
What synaptic changes ultimately cause executive functioning defecits in addiction?
- Changes in (stress associated) CRF, noradrenaline and dynorphin
- Balance between glutamate and dopiminergic neurons in the VTA and amygdala also underly the chnages in executive function
Is the pattern of altered activity due to drugs global?
No, each drug has its own pattern of activity
What does long-term potentiation of GABAergic synapses onto VTA DA neurons cause?
Leads to disinhibition of DA neurons in VTA
What does synaptic plasticity in the VTA trigger?
- Triggers subsequent synaptic plasticity in other parts of the mesocorticolimbic pathway
- The accumbens receives glutamatergic inputs from cortical (PFC) and limbic (amygdala) brain regions
- LTP in glutamaterfic activity between PFC and striatal medium spiny neurons occurs after repeated exposure to a substance
- Subunit changes in NMDA/AMPA receptors as well as the shift in balance of currents, Ca sensitivity of subunits etc all contribute to changes in synaptic activity
What changes occur at the individual neuron level in addiction?
Changes occur in the NA and VTA neurons and these can be the size of the dopaminergic neurons (decrease) or increased dendritic branching
What are some unique pharmacological and pharmodynamic properties which can be drug specific?
- Receptor binding
- Signalling profiles
- Cellular localisation
What do spatial aspects of localisation lead to in terms of different pharmacological effects at the plasma membrane?
- MOP ligands (mu opioid ligands))
- 5HT2A ligands
What are three common hedonic effects associated with NA dopamine influx?
- Stimulation and/or sedation
- Mood elevation
- Intense euphoria (initially acute rush- then prolonged high)
What are 4 psychostimulants?
- Cocaine
- Amphetamines
- MDMA
- Cathinones (bath salts)
Where does cocaine act?
Inhibit noradrenaline (NAT/NET), serotonin (SERT) and dopamine (DAT) transporters
What effects does cocaine cause?
- Pleasure- DAT and SERT
- Stimulant effect- NAT/NET
What happens when smoking crack cocaine?
- Rapid rush within seconds
- Rapid intense crash
Where does amphetamine act?
- Inhibits DAT
- Taken up into the presynpatic terminal and inhibits VMAT and the filling of vesicles with transmitter
- Reversal of DAQT direction and cytoplasmic DA released into synapse (increase EC dopamine)
- Also has effects on NAT/NET and SERT
What are MDMA’s actions?
- Inhibits DAT, NAT/NET/ SERT
- Primary effects through the release of 5HT
- Can cause serotonin syndrome
What is serotonin syndrome?
- Profound hyperthermia
- Altered mental states
- Movement disorders
What is the cathinones method of action?
- Increase release of NA, DA and 5HT
- Inhibit transporters NAT/NET, DAT, SERT
- Not easily detected in urine and toxicology screens
Through what methods do cannabinoids work?
Modulate mesolimbic DA through CB1 and CB2 receptors