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Lesson 3
The Science of Nicotine Addiction
Where does nicotine go in your body?
It goes to your lungs, and then via the bloodstream to your heart
and all parts of the body, including your brain.
How does the body get rid of nicotine?
• Nicotine circulates
throughout the body in the
bloodstream.
• Eventually it is carried to the
liver, where enzymes break
it down into other
compounds.
• These compounds are
carried by the bloodstream
to the kidneys and then
excreted from the body in
urine.
A look at the brain
Different parts of the brain are involved in different functions, like
vision, movement, thinking, memory.
The Reward Pathway
The reward pathway is a neural pathway used for
reinforcing behaviors that are important for survival.
Nicotine also stimulates the reward pathway.
This feels
Eating
makes
me
happy!
good!
To understand how
this works, we need
to learn about
neurons and
neurotransmission...
Neurons
• Have a cell body, dendrites, and axon
• Use electrical impulses and chemical signals
Neurotransmission is…
The process of transferring messages between neurons.
Its purpose is to carry signals from one part of the brain to
another or to other parts of the body, like muscles.
Synapse
Dopamine is the neurotransmitter in the
reward pathway
Stimulation of neurons in the VTA area results in release of
dopamine in the NA (emotional center) and the prefrontal cortex
(thinking).
(NA)
(VTA)
How Does Nicotine Interact with
Neurotransmission and the Reward Pathway?
This
feels
good!
Nicotine binds to receptors
on neurons in the ventral
tegmental area.
An electrical impulse
travels down the neuron
axon.
Dopamine is released at
axon terminals in the
nucleus accumbens and
prefrontal cortex.
Dopamine binds to dopamine
receptors on other neurons.
This leads to the rewarding
effects of smoking, such as
relaxation, a “buzz”, or an
increased ability to focus.
What is the impact of nicotine
interacting with the reward
pathway?
Addiction!
What genes might be involved in differences in
smoking behavior?
Nicotine
receptors
Dopamine receptors;
enzymes that make or
break down dopamine
Enzymes involved in
nicotine breakdown
The reward pathway is involved in
other addictive behaviors
• Cocaine slows the re-uptake of
dopamine in the nucleus
accumbens.
• Methamphetamine results in
increased dopamine release as
well as blocking the re-uptake of
dopamine in the nucleus
accumbens.
• Other addictive behaviors, like
gambling and risk taking involve
the reward pathway.
What are some benefits of identifying
variants in genes associated with
smoking behavior?
• Increasing our understanding for the addiction process
• Helping people understand their own risk for becoming
addicted to nicotine or other addictive drugs or behaviors
• Helping to choose the best cessation program for an
individual based on their genes
What are some risks of identifying
variants in genes associated with
smoking behavior?
• The same gene variants may also be associated with the
use of other addictive drugs or addictive behaviors. By
learning about genes that affect smoking behavior, people
also get information about other behaviors (which they
may not want). A gene that affects different traits is called
pleiotropic.
• People who carry a risk variant may face discrimination
getting jobs, health insurance, or life insurance.
• The frequency of a risk variant may be higher in a certain
group, leading to stigmatization of that group.