Addiction and the brain Flashcards
What is the primary role of dopamine in motor regulation?
Motor regulation involves the nigrostriatal pathway and the substantia nigra compacta projecting to the basal ganglia.
Which pathway is associated with personality, perseverance, and compulsions?
The mesocortical pathway, where the ventral tegmental area projects to the prefrontal cortex.
What are the functions of the mesolimbic pathway?
The mesolimbic pathway is involved in reward, euphoria, and intense emotions, with the ventral tegmental area projecting to the nucleus accumbens.
Where is the ventral tegmental area (VTA) located?
In the midbrain (mesencephalon).
What percentage of dopaminergic neurons are found in the VTA?
About 50-60% of dopaminergic neurons.
What neurotransmitter regulates the activity of dopaminergic neurons in the VTA?
GABA.
What is the role of GABAergic interneurons in the mesolimbic pathway?
They provide tonic inhibition of dopamine neurons.
What effect does a reward or cue with an expected reward have on VTA dopaminergic neuron firing?
It leads to increased firing.
Fill in the blank: Dopamine sensitivity is linked to personality traits like _______.
extraversion, sensation- and reward-seeking.
True or False: Dopamine is targeted by most chemically addictive drugs.
True.
What happens to dopamine receptors when there is an increase in dopamine levels?
Receptor internalization occurs, leading to fewer receptors.
What is the main precursor for dopamine synthesis?
L-Dopa.
What can too much L-Dopa cause?
Mania.
What types of drugs increase dopamine release from VTA neurons?
Opioids, heroin, cocaine, amphetamines, cannabinoids, benzodiazepines, nicotine, alcohol.
List the drug groups and their effects: Opiates, Stimulants, CNS depressants, Hallucinogens.
- Opiates: reduce pain
- Stimulants: increase alertness, intensify mood
- CNS depressants: increase drowsiness, relax
- Hallucinogens: alter perceptions, thoughts.
What enzymes are involved in dopamine breakdown?
COMT and MAO.
What is the effect of COMT variants on dopamine levels?
- Slow form: linked to better concentration, cognitive skills/IQ
- Fast form: linked to better stress response.
How does nicotine affect dopamine pathways?
It activates mesolimbic and mesocortical dopamine pathways and projects to the TPP.
What is the function of dopamine reuptake inhibitors (DRIs)?
They inhibit the dopamine transporter (DAT), resulting in elevated dopamine transmission.
What are some clinical uses for norepinephrine dopamine reuptake inhibitors (NDRIs)?
Depression, ADHD, narcolepsy, Parkinson’s disease.
Fill in the blank: Cocaine and amphetamines are examples of _______.
SNDRI (serotonin-norepinephrine-dopamine reuptake inhibitors).
What are the two main types of endogenous opioid peptides involved in the reward system?
β-endorphin (μ receptor) and Enkephalins (δ receptor)
Both are implicated in the activation of the mesolimbic dopamine system and are associated with drug addiction.
What system is activated by endogenous opioid peptides, leading to increased dopamine?
Mesolimbic dopamine system
Specifically from the ventral tegmental area to the nucleus accumbens (NAC).
What is the significant statistic regarding fentanyl overdoses in the USA in 2016?
20,000 overdoses
This highlights the severity of the opioid crisis.
What do heroin and codeine metabolize into?
Morphine
This metabolic pathway is crucial for understanding opioid effects.
What enzyme is involved in the metabolism of codeine to morphine?
CYP2D6
Genetic variations in CYP2D6 can affect the metabolism rate.
What does a Morphine: Codeine ratio greater than 1 indicate?
Use of morphine or heroin
Genetic rapid metabolisers may show a higher ratio.
What are endorphins associated with?
Pain, pleasure reward, and addiction
They play a role in the perception of exercise and reward.
True or False: The majority of people experience a ‘runner’s high’.
False
Most individuals report feelings of nausea or tiredness instead.
What are the two main biological theories of exercise addiction?
Endorphins theory and endogenous cannabinoid theory
These theories attempt to explain the psychological effects of exercise.
What is the prevalence of exercise addiction?
5-14%
This indicates that addiction to exercise is quite rare.
What are the reasons the endorphin theory of exercise addiction is considered unlikely?
a) Endorphins do not pass the blood-brain barrier.
b) Mixed results from studies with opioid antagonists.
c) Modulation by exercise intensity.
These points suggest other mechanisms may be at play.
What psychological conditions are associated with exercise addiction?
OCD, anxiety, stress, substance abuse, reward sensitivity, eating/body image disorders
These conditions may be secondary to achieving non-exercise related goals.
What is Internet Gaming Disorder (IGD) associated with?
Reward deficiency, reduced impulse control mechanisms, impaired decision making, and impulsivity
These features are common in various types of addiction.
What neurobiological alterations are seen in IGD?
Activation in reward-associated brain regions and reduced activity in impulse control areas
This reflects similarities with drug addiction.
How does ADHD relate to Internet Gaming Disorder?
Less sensitivity to dopamine and impaired executive control may increase susceptibility
Adolescents with ADHD may use cyber games to enhance focus.
What are the offenses outlined in the Misuse of Drugs Act?
- Unlawfully possess a controlled drug
- Possess a controlled drug with intent to supply
- Unlawfully sell/give/share a controlled drug
- Allow premises to be used for drug use
These offenses highlight legal implications of drug misuse.
What are some effects of alcohol on the brain?
- Increases dopamine concentration
- Decreases serotonin neurotransmission
- Stimulates opiate neuropeptide release
- Potentiates GABA receptor function
- Inhibits Glutamate receptor function
These effects contribute to the psychoactive properties of alcohol.
How does alcohol affect the opioid reward system?
Alcohol interacts with the binding properties of opioid receptors and modulates opioid peptide synthesis
This relationship is important for understanding alcohol’s addictive potential.
What is one model proposed for alcohol reward?
Activation of μ-opioid receptors in the VTA and/or δ-receptors in the NAC
Endogenous β-endorphin targets these receptors.
What physiological response does sugar stimulate?
Dopamine production
This relates to the mechanisms underlying eating disorders.
Fill in the blank: A drop in sugar causes _______.
Hunger
This reflects the body’s regulatory mechanisms for energy balance.
What happens to individuals who become resilient to insulin?
They won’t feel full
This can lead to issues like diabetes and overeating.
