Download Neurobiology of Addiction

The Reward Pathway
And Addiction
Based on a teaching presentation
developed by the National
Institute on Drug Abuse
www.nida.nih.gov
REWARDS
• Natural
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Food
Water
Sex
Nurturing
• Artificial
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Electronic games
Shopping
Texts and tweets
Gambling
Drugs (both natural and
synthetic)
Rewards reinforce and
motivate behavior
THE BRAIN’S REWARD PATHWAY
Neurons of VTA release dopamine in the nucleus accumbens and
prefrontal cortex
Cellular Targets in the Brain
SUBSTANCE USE and
ABUSE
Activation of the reward
pathway by a substance that
provides a “rewarding”
stimulus
“Positive
reinforcement” results in
repeated use of the substance
ADAPTATION AND
TOLERANCE
Repeated activation of neuron by drug

Neuron chemically adapts and alters
intensity of cellular response to drug

Desired effect of drug decreases
DEPENDENCE
Exogenous administration of drug replaces
brain’s production of endogenous
chemical
Neurons now only function normally in
presence of drug
ADDICTIVE BEHAVIOR
Use continues, even with negative
consequences and in absence of
pleasurable results (i.e. in order to
maintain a “normal” brain environment)
WITHDRAWAL AND
CRAVINGS
If drug is not available to the neuron,
unpleasant emotional and physical
effects occur, because the normal
activating and inhibitory
neurotransmitter levels have
been altered
See example, next slide
Example: Addiction to stimulants causes lack of synaptic availability of
DA and Serotonin 5-HT. When stimulants not available, the addicted person
experiences associated cravings and withdrawal symptoms.
Rothman, Blough, Baumann
AAPS Journal, Vol. 1, 2007