Drug Dependency Flashcards
Define addiction
Chronic disease characterised by drug seeking
Compulsive and difficult to control despite harmful consequences
Define drug abuse
Pattern of drug use in which individual is using methods/amounts of substance which directly/indirectly harm themselves and/or others
Define drug dependence
Adaptive state that develops after repeated drug use (withdrawal symptoms)
Define psychological dependence
Dependence involving emotional/motivational withdrawal symptoms (e.g. depression/restlessness/dysphoria)
Define physical dependence
Dependence involving significant physical-somatic withdrawal symptoms (e.g. fatigue/nausea/seizures/pain)
Which drugs are the most harmful?
Alcohol
then heroin, crack cocaine, meth
What do opiates target?
Mu and delta opoid receptors
What does cocaine target?
DA (dopamine) , NAd (noradrenaline) and 5-HT uptake systems, inhibiting them
What does amphetamine target?
monoaminergic transmission amplifier: uptake systems, agonist of trace amine associated receptor 1
What does ethanol target?
GABA and NMDA receptors (glutamate) modulating both excitatory and inhibitory systems in the brain
What does nicotine target?
nicotinic receptors
What do cannabinoids target?
CB1 receptors
What do phencyclidine and ketamine target?
NMDA glutamate receptors
What do hallucinogens target?
5-HT2A receptors
What do barbiturates and benzodiazapines target?
- GABAa receptors
What 3 factors determine addiction development?
- environment
- drug induced effects (pleasant/unpleasant, in pleasure there is a decrease in the occupancy of dopamine receptors)
- genes (polymorphisms in the opoid MU, kappa and delta receptors)
What are the 3 stages of the addiction cycle?
- binge/intoxication (positive reinforcement)
- withdrawal/negative affect (negative reinforcement)
- preoccupation/anticipation (conditioned positive and negative)
What are the core clinical symptoms of addiction?
Intoxication
bingeing
withdrawal
craving
What is the withdrawal mechanism?
- acutely dopamine from the VTA stimulates the nucleus accumbens (reward system) causing pleasure
- nucleus accumbens projection neurons releasing transmitters on the VTA’s kappa opoid receptors and act as regulatory break
- drug abuse inhibits VTA = dopamine release reduced = dysphoria
What is the VTA?
ventral tegmental area
origin of dopaminergic cell bodies, mesocorticolimbic dopamine system and other dopamine pathways
natural reward circuitary of the brain
What is the mechanism of drug dependence?
- involves excitatory amino acids and dopamine
- when you crave the drug you know there are certain activities you need to get it so gives rise to planning of taking the drug making your a brain a slave to impulse
- also reduced availability of D2 receptors and reduced metabolism
What structures are involved in drug dependence?
- involved in craving/planning/taking:
VTA, nucleus accumbens, amygdala, insula, PFC, hippocampus
What is the mechanism of neuroplasticity in drug-seeking behaviour?
More dependent you become = more compulsive/uncontrolled you are to take it
- loss of control over various CNS structures
What changes are there to the prefrontal cortex in addiction?
impaired processes associated with PFC:
- self control and motivation
- emotional regulation
- attention and flexibility
- working memory
- decision making
- awareness and insight
- learning and memory
- salience attribution
How is chronic drug abuse related to gene regulation?
- addiction changes gene expression throughout the brain
- increased expression of FosB gene
What is the alcohol consumption indicative of abuse?
Regular consumption of:
M - 5 units a day
W - 3 units a day