Week 4 Flashcards
Is there a single, universally accepted definition of addiction?
no
What did Eric Nestler define drug addiction as?
The compulsive seeking and administration fo a drug despite consequences
What did Volkow, Koob and McLellan describe addiction as
the most severe, chronic stage of substance use disorder, loss of self control
What does the national institute for drug abuse define addiction as?
chronic, relapsing brain disease that is characterised by compulsive drug seeking and use despite harmful consequences.
Who came up with the perspective that addiction was a brain disease?
Alan Leshnew, director of NIDA
Instead of addiction, what do these types of disorder come under in the DSM-5?
- substance use disorders
2. substance induced disorders
What are substance use disorders according to the DSM-5?
a cluster of cognitive, behavioural and physiological symptoms and continued use of substance.
What are substance induced disorders according to the DSM - 5?
substance intoxication, withdrawal and other substance/medication induced mental disorders.
How many symptoms indicate either a mild, moderate or severe substance use disorder?
- 2-3
- 4-5
- 6 or more
What is tolerance in addiction?
Need for increased amounts of substance to achieve desired effect
How does the addiction cycle usually begin?
Positive reinforcement models suggest that the pleasurable effects of using a drug reinforce initial drug use.
Negative reinforcement explains that initial drug use is due to escaping emotional distress.
Over time, the rewarding effects of drug use are reduced and compulsive drug taking behaviour results from a need to achieve a state of homeostatis i.e., for the individual to feel normal or to alleviate pain. What type of reinforcement is involved here?
Negative reinforcement.
Addiction shares features of both ____ and ____ disorders.
impulsive and compulsive
What did George Koob propose in regard to addiction?
There is a shift from impulsive to a compulsive disorder as there is a shift from positive to negative reinforcement driving drug seeking behaviour.
The concept of reward pathways is controversial. Why is this?
Has the brain really evolved to express dedicated neural systems specifically devoted to encoding reward or pleasure? Maybe the brain has systems that subserve motivated behaviour, which drugs compromise.
Dopamine is released when we experience what?
Food, sex, drugs.
When exactly is dopamine released?
BEFORE a pleasurable activity.
What other pathways which research has implicated in addiction?
the mesolimbic and mesocortical pathways.
Studies demonstrated that rats quickly learned to press a lever fo self administer intravenous injections of cocaine and other addictive drugs and would do so despite:
Grave consequences.
e.g., would sacrifice drink or food, abandon their newborn pups.
Lesioning the dopamine system at the level of the nucleus accumbens does what regarding the acquisition of cocaine?
prevents it - suggesting that dopamine mediates, at least in part, the reinforcing effects of these two drugs.
Drug addiction is often characterised by anhedonia. What does this mean?
Failure to experience rewarding stimuli.
What has other research potentially implicated in drug addiction?
- serotonergic system
- GABA
- glutamate
Exposure to addictive drugs changes the brain, both structurally and functionally. Addiction leads to enduring changes in:
- synaptic plasticity
- dendritic size and spines
- changes in white and gray matter
- up/down regulation of receptors
- changes in intracellular signalling pathways
Which two receptors have been shown to be involved in long term potentiation?
NMDA and AMPA
Cocaine exposure has been found to result in ____ long term potentiation in the ventral tegmental area, lasting for days to months after cessation of treatment.
increased
What is drug sensitisaion?
enhanced response of the drug that is observed following repeated exposure (reversed tolerance)
Sensitisation ___ excitability of dopamine neurons.
enhances
What effect did amphetamine have on dendrites?
Increased the size and number of spines
What did Juan’s research indicate regarding which area of the brain becomes hyper excitable following chronic amphetamine exposure?
nucleus accumbens
What was found in the shape of the dendrites in a study with rats self administering cocaine, located in the prefrontal cortex?
They were misshapen, with large, bulbous structures at their tips.
What has been found in gray matter in substance use disorders?
Gray matter volume reductions. Drug craving is negatively associated with gray matter volume in multiple brain regions.
White matter refers to tracks of myelinated axons. What has been found in those individuals with substance use?
loss of cerebral white matter
What is substance use related to in regard to dopamine receptors?
decreased density of postsynaptic dopamine receptors.
Reduction in what receptor function is an important feature in addiction?
Dopamine D2 receptor
Repeated drug exposure makes neurons adapt over time. These cellular changes are believed to be responsible for:
- tolerance
- addiction
- withdrawal
An increase in phosphorylated CREB correlates with what?
diminished sensitivity to drug induced reward.
Contrary to CREB, over-expression of ΔFosB
increases sensitivity to the rewarding and reinforcing effects of stimulants
Dopamine antagonist does what?
binds and blocks the D2 receptor
What competes with dopamine for binding in the brain?
raclopride. Therefore, high dopamine lads to low raclopride binding and vice versa.
Cocaine abusers showed ___ dopamine increases and reported reduced rewarding effects of methylphenidate
decreased
What does decreased dopamine in the brain lead to?
- depressive like symptoms (hypodoraminergia)
- anhedonia
- decreased activation of prefrontal cortex
Decreased dopamine has been shown to be associated with:
increased preference for drugs
One study showed that impulsive rats (who had less dopamine):
struggled to inhibit getting the drug
