Explanations for nicotine addiction: brain neurochemistry
Role of dopamine
Desensitisation hypothesis: nicotinic receptor can bind w Ach (acetylcholine) or
nicotine. When nicotine binds w nicotinic receptors the neuron becomes
stimulated and transmits dopamine. immediately after this leads to
desensitisation of the neuron, which leads to downregulation = a reduction in
no of active neurons as fewer are available.
Nicotine addiction occurs because nicotine binds w nicotinic receptors
(nAChRs) in the ventral tegmental area of the brain. This triggers the release of
dopamine in the nucleus accumbens in the mesolimbic system (this is the
reward centre of the brain). Activation of this reward pathway creates euphoria
and reduced anxiety, these effects become associated w smoking through
operant conditioning.
Nicotine regulation model (Withdrawal): as long as a person is smoking,
nAChRs are continually desensitised. Abstinence leads nicotine to disappear
from their body and the ACh receptors become functional and neurons
become sensitised. The person will experience withdrawal symptoms from lack
of nicotine as during resensitisation nAChRs become overstimulated by Ach
(acetylcholine) as there is no nicotine to bind w them, this Ach is associated w
decreased dopamine functioning. The smoker is then motivated to avoid
unpleasurable physiological and psychological withdrawal states by having
another cig.
Role of dopamine
Desensitisation hypothesis: nicotinic receptor can bind w Ach (acetylcholine) or
nicotine. When nicotine binds w nicotinic receptors the neuron becomes
stimulated and transmits dopamine. immediately after this leads to
desensitisation of the neuron, which leads to downregulation = a reduction in
no of active neurons as fewer are available.
Nicotine addiction occurs because nicotine binds w nicotinic receptors
(nAChRs) in the ventral tegmental area of the brain. This triggers the release of
dopamine in the nucleus accumbens in the mesolimbic system (this is the
reward centre of the brain). Activation of this reward pathway creates euphoria
and reduced anxiety, these effects become associated w smoking through
operant conditioning.
Nicotine regulation model (Withdrawal): as long as a person is smoking,
nAChRs are continually desensitised. Abstinence leads nicotine to disappear
from their body and the ACh receptors become functional and neurons
become sensitised. The person will experience withdrawal symptoms from lack
of nicotine as during resensitisation nAChRs become overstimulated by Ach
(acetylcholine) as there is no nicotine to bind w them, this Ach is associated w
decreased dopamine functioning. The smoker is then motivated to avoid
unpleasurable physiological and psychological withdrawal states by having
another cig.
