Explanations for nicotine addiction: brain neurochemistry AD Flashcards
Neurochemistry
relating to chemicals in the brain that regulate biological and psychological functioning
Dopamine
a neurotransmitter that generally has an excitatory effect and is associated with the sensation of pleasure. Usually high levels are associated with schizophrenia and usually low levels are associated with parkinson’s disease
Dani and Heinemann
focussed on dopamine in their desensitisation hypothesis of nicotine addiction and the neurotransmitter acetylcholine.
nAChRs
n=n icotine
Ach= acetylcholine
Rs= receptors
Acetylcholine ACh plays a role in all nervous system activity, which means that….
they are on the surfaces of most neurons in the CNS.
The subtype nicotinic acetylcholine receptors (nAChR) are activated by nicotine molecules and then transmits dopamine. This then……..
gets followed by shutdowns where the nAChR temporarily cannot respond to neurotransmitters. This is when the neuron is desensitised, which leads to downregulation (a reduction in the number of active neurons because fewer of them are available)
Where are nAChR concentrated?
the ventral tegmental area VTA of the brain
What happens when nAChR are stimulated by nicotine?
dopamine is transmitted along the mesolimbic pathway to the nucleus accumbens NA, which triggers the release of more dopamine into the frontal cortex.
Simultaneously, dopamine is also transmitted along the mesocortical pathway to be released directly into the frontal cortex.
wat activates the brain dopamine reward system?
nicotine, results in pleasurable effects such as mild euphoria, increased alertness and reduction of anxiety. These effects become associated with smiling through operant conditioning.
withdrawl
As long as the person is smoking, nAChRs are continually desensitised. But when this person does not smoke for a prolonged period of time nicotine disappears from their body. The nAChRs become functional again and dopamine neurons resensitise and more become available (upregulation).
During this time, the person will experience withdrawal symptoms.
dependance and tolerance
Smoker avoids unpleasant physiological and psychological withdrawal by having another cigarette. This means that there is a constant cycle of daytime downregulation and night-time upregulation (from sleeping) creates long term desensitisation of nAChRs.
What does continuous exposure of nAChR to nicotine cause?
permanent changes to the brain neurochemistry → a decrease in the number of active receptors
tolerance
develops as a smoker has to smoke more to get the same effect.
Research support -
Support from human research
strength
- McEvoy et al studied smoking behaviour in people with schizophrenia who were taking a antipsychotic drug
- This drug blocks dopamine receptors in the brain, reducing dopamine transmission
- So people taking the drug had increased levels of smoking presumably from self-medicating
Supports the view that dopamine has a key role in the neurochemistry of nicotine addiction.
counterpoint to RS -Counterpoint
Explanations of nicotine addiction that consider only the role of dopamine are limited
limitation
- Research increasingly shows complex interactions of several neurochemistry systems
-
Watkins et al said these include neurotransmitter pathways and endogenous opioids
Therefore the neurochemistry of nicotine addiction cannot be fully understood by just looking at dopamine.
