NICOTINE ADDICTION: BRAIN CHEMISTRY

Nicotine

it binds to the nicotinic acetylcholine receptor

nicotine imitates the action of a natural neurotransmitter called acetylcholine

dopamine reward pathway

  1. trigger the release of the neurotransmitter dopamine the nucleus accumbens - leading to feeling of pleasure
  1. boosts activity in the prefrontal cortex
  1. nicotine binds to the nicotinic acetylcholine receptor sites on the neurons of the VTA

pleasure encourages the individual to repeat the smoking behaviour

downregulation and upregulation

smokers develop a tolerance to nicotine and experience reduced pleasure from it over time

they become desensitised to the effects of nicotine, they need to smoke more to achieve the same desired effect

chronic smokers maintain a high enough concentration of nicotine to deactivate the receptors and slow down their recovery, cannot be triggered by acetylcholine - downregulation

nicotine regulation model

individuals smoke to avoid withdrawal symptoms

due to nicotine levels in the blood dropping

causes a decrease in dopamine levels

become sensitive to the effects of acetylcholine again, resulting in feelings of anxiety, agitation and restlessness

research support - watkins et al. 2000

found that dopamine release was reduced following chronic exposure to nicotine

explains how a tolerance to nicotine develops over a time as the level of reward felt decreases with prolonged exposure

research into neurobiology of nicotine addiction

partial explanation

there are many other neurochemical mechanisms involved and that there is a vastly complex interaction of neurochemical systems

eg GABA and serotonin

dopamine is only part of the neural action, there are several complex explanations

however dopamine is arguably central to the neurochemistry of nicotine addiction

DRD2 gene

comings et al found that nicotine addicts show a greater prevalence of the A1 variant of the DRD2 gene

48% in smokers, compared to 25% amongst non smokers

dopamine could further support the idea that there is a genetic link to smoking addiction

related to fewer dopamine receptor sites and lower levels of dopamine in the brain

therefore lead them to feel the rewarding effects of nicotine to a greater extent

reductionist

only explains nicotine addiction on a biological level, psychological and social factors also play an important role in nicotine addiction

cannot offer a complete explanation for nicotine addiction.

neurochemical explanation is considered to be reductionist