The role of Dopamine

How does the NIAAA describe addiction?

Caused by chronic self administration of drugs that produce changes in brain neurotransmitter systems that leaves addicts vulnerable to relapses after abstinence.

What is the key brain area implicated in addiction?

Mesolimbic pathway

What is the explanation for the role of mesolimbic pathway?

It is the reward pathway, rewarding behaviours make sense to repeat and it is not just rewarding behaviours but also drugs that are rewarding.

What did Wise 2008 find?

DA neurons located in the ventral regimental area and project to nucleus accumbens play a key role in reward processing including those associated with drugs.

What does DA signalling actually do?

Encodes for a reward prediction signal and salience.

What did Shultz 2002 find about withdrawal?

Primates trained to associate a cue with food (pleasure) increased dopaminergic activity in response to cue but if food wasnt presented dopaminergic activity would drop leading to negative emotion (dysphoria).

What evidence shows that its not just dopamine or mesolimbic pathway?

Frontal cortex has been questioned in the maintenance of addiction, when addicts tolerance and withdrawals disappear many still relapse and start using again. Suggests frontal lobe could be altered and so reasoning is as well.

What does Volkow suggest about frontal cortex?

Changes to frontal cortex can alter our attention causing addicts to pay more attention to stimuli associated with their addiction.

What does Robinson and Berridge (2003) find regarding frontal cortex?

Changes cause addict to feel compelled and want to engage in addictive behaviour rather than just like it.

How does the Brain adapt to addictive behaviour?

Neuroadaptation is a process where the brain attempts to achieve a balance to return to equilibrium. Drug use disrupts balance and adapts to minimise effect of drug to restore normal function and when drug no longer used adaptations remain so cause withdrawals.

How is tolerance built?

When drug taken repeatedly effects are diminished so higher doses required to achieve the same effect.

What did Volkow et all (1997) find regarding cocaine users?

Reduction in both the number of D2 receptors in the brain as well as reduction in the release of dopamine

What was Olds and Milner (1954) study?

Placed electrodes on regions of rats brain (pleasure centre) everytime went they went to the corner of the box. Rats kept returning to the same corner.