1. The Reward Pathway And Addiction
Based on a teaching presentation developed by the National Institute on Drug Abuse

2. REWARDS Natural Artificial Food Water Sex Nurturing
Drugs (both natural and synthetic)
Pleasurable feelings
reinforce a behavior

3. THE BRAIN’S REWARD PATHWAY
Neurons of VTA release dopamine in the nucleus accumbens and
prefrontal cortex

4. 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

5. Cellular Targets

6. 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

7. DEPENDENCE
Exogenous administration of drug replaces brain’s production of endogenous chemical
Neurons now only function normally in presence of drug

8. ADDICTIVE BEHAVIOR
Use continues, even with negative consequences and in absence of pleasurable results

9. 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

10. experiences associated cravings and withdrawal symptoms.
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