The Science of Nicotine Addiction

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Lesson 3

• The Science of Nicotine Addiction

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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.
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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.

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A look at the brain

• Different parts of the brain are involved in
  different functions, like vision, movement,
  thinking, memory.

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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 good!
To understand how this works, we need to learn
about neurons and neurotransmission...
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Neurons

• Have a cell body, dendrites, and axon
• Use electrical impulses and chemical signals

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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
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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).

(VTA)
(NA)
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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.
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What is the impact of nicotine interacting with
the reward pathway?

• Addiction!

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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
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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.

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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

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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.