Biological Explanation - Dopamine Flashcards
Mesolimbic pathways
Reward pathway
Consist of: ventral tegmental area - release dopamine when accomplished tasks (eating, finishing work)
Nucleus accumbens - pleasure it felt when it present of dopamine
Negative addictive acts also activate this system
Joshua et al - dopamine level up in participants during gambling task whether or not win
Lead to salience - addiction becomes hobby
Tolerance + withdrawal
When exposed to drug - brain train to regain equilibrium to remain normal function - neuroadaptation (brain develop more receptors)
-if use repeatedly presence of drugs becomes the norm = changes in brain considered normal
Volkow et al - cocaine user has reduced D2 dopamine receptor + less dopamine released
If no drugs = brain not in equilibrium
-cause withdrawal effect - want to take drugs to go back to normal - take a long time for brain to adapt to no drug
-no take for pleasure, take for avoid withdrawal
Role of frontal cortex
Volkow et al - excess dopamine release cause abnormalities in frontal cortex, change attention ability - pay more attention to stimuli associated with addiction
Robinson and Berridge - addict feel compelled to do addiction even when no pleasure - explain relapse - instinct to carry out addiction
Evaluation - causal relationship
Can explain how individual progressively become addicted - develops tolerance + withdrawal
Explain relapse - by brain abnormalities
Allow for therapies to be developed - drugs
Contradicting evidence
Stokes et al - no significant change in dopamine lvl in participant who took cannabis
-not as credible, may be other variables are problem (environment or role of gene)
Also does not explain how addiction is started
Ignore individual difference
Does not explain why some people more likely to be addicted or not
-if dopamine only explanation = everyone react same way to drugs
NHS - 9% of white British male takes drug in uk, only 3% of Asian do
A1 variant of DRD2 gene - link with D2 dopamine receptor
-those with lower activity less receptor = less stimulated - more likely to indulge more in addiction since more tolerant
Applying explanation to agonist + antagonist
Therapy -
Agonist - reduce withdrawal similar structure to opioids but no high
Antagonist - reduce relapse - no high since blocked receptors
Mesolimbic system - high trigger due to nucleus accumbens receive dopamine from receptors
Block mesolimbic ability to receive dopamine = no high from antagonist or used for detoxification to revert receptors + NT from mesolimbic system to normal
