Nicotine addiction: Brain chemistry and dopamine Flashcards
What is the candidate gene for smoking addiction?
One candidate gene for smoking (and other addictions) is the A1DRD2 variation.
This seems to code for defective and insufficient dopamine receptors in the brain’s reward circuitry, meaning some individuals cannot produce pleasure naturally and may engage in smoking behaviours to raise dopamine to optimal levels
What is the first step of the role of dopamine?
Nicotine stimulates specific acetylcholine receptors which increases alertness, memory function and learning.
What is the second step in the role of dopamine?
This action causes a rise in dopamine activity in the ventral tegmental area (VTA): a critical area in the brain’s reward circuitry which is highly populated with NAcRs. This gives nicotine a rewarding sensation.
What is the third step in the role of dopamine?
The VTA activity caused by nicotine is then projected to the nucleus accumbens, a producer of dopamine that is located deep in the mesolimbic dopamine pathway
What is the fourth step in the role of dopamine?
The nucleus accumbens is a primary reward centre in the brain and with increased activity dopamine rises, causing users to evaluate smoking is very pleasurable, compelling further use.
What is the fifth step in the role of dopamine?
Furthermore the nucleus accumbens is encouraged to release more dopamine as nicotine also stimulates endorphins that reduce GABA activity. A decrease in GABA correlates with further rises in dopamine. More and more dopamine forces smokers to engage with further use.
What is upregulation?
Comes after step four. The number of receptors increase in response to the rising levels of nicotine so as a reward the smoker wants this feeling again
What is downregulation?
Smoker’s reward system becomes less sensitive which can create negative feelings, meaning that the smokers will continue to smoke more and more.
What is the first step in smoking relapse?
As nicotine triggers the firing of dopamine in the mesolimbic dopamine pathway, and this acts like a reward or a ‘kick’ to the smoker (upregulation). As a reward the smoker wants this again, but tolerance develops.
What is the second step in smoking relapse?
With LT use, the Nicotine Regulation Model (Shachter, 1977) suggests that the smokers ‘reward system’ becomes less active/sensitive (downregulation) i.e specific nicotinic acetylcholine receptors (nAchRs) become unavailable and inactive. (This can create anxiety, lethargy and sadness)
What is the third step in smoking relapse?
To avoid this, smokers continue to smoke more to maintain a certain level of nicotine in their bodies to avoid these unpleasant side effects (negative reinforcement)
What is the fourth step in smoking relapse?
Hence, with the downregulation (tolerance) in the mesolimbic pathway, an increased amount of nicotine is needed to achieve the same initial ‘kick’ as the rewarding receptors have been ground down
BRAIN CHEMISTRY IN NICOTINE ADDICTION - Supporting research?
Research by Paterson’s et al (2002) found support for the role of nicotine and dopamine through research with the epilepsy drug (Gamma-vinyl GABA).
This drug (G-v GABA) reduces the surge of dopamine in the nucleus accumbens that occurs after nicotine. This effectively reduces the addictive properties of nicotine, without major side effects
BRAIN CHEMISTRY IN NICOTINE ADDICTION - Gender bias?
Suffers from Beta bias.
Research by Nerin and Jane (2007) argues that the onset of smoking addiction is significantly different between the sexes i.e. women typically start smoking much later than men. The biological reasoning for this is ignored and not explored.
BRAIN CHEMISTRY IN NICOTINE ADDICTION - Individual differences?
Not everyone becomes addicted. These individual differences must mediate the chances of repeating the behaviour and becoming addicted such as your own personality or if you have a high internal locus of control, where you perceive that you have have control over your actions. This can have a big impact on the chances of you becoming addicted.
