How does addiction occur.

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How does addiction occur.

  1. 1. HOW DOES ADDICTION OCCUR?
  2. 2. Dopamine Pathways Functions •reward (motivation) •pleasure, euphoria •motor function (fine tuning) •compulsion nucleus accumbens hippocampus striatum frontal cortex substantia nigra/VTA raphe
  3. 3. Neuronal structure (receiving) (sending)
  4. 4. /serotonin Vmat transporter stimulation How some drugs of abuse cause dopamine release: • opioids narcotics (activate opioid receptors) • nicotine (activate nicotine receptors) • marijuana (activate cannabinoid receptors) • caffeine • alcohol (activate GABA receptors; an inhibitory transmitter) Drug : • cocaine • ritalin vesicle Neuronal terminal
  5. 5. • Release DA from vesicles and reverse transporter Drug Types: • Amphetamines -methamphetamine -MDMA (Ecstasy) Vmat transporter serotonin/
  6. 6. • Principles of Behavior Dynamics Behavior Tracts Compete for Expression  Expression is Determined by (i) Dominance of Tracts, (ii) Strength of Prefrontal Cortex to Select, (iii) Relevance or saliency (orbitofrontal cortex) A B C Prefrontal Cortex Cbehavior expressed Bbehavior expressed Activation of Dopamine reward pathway initiates a behavior track dopamine initiated (Miller & Cohen, Annu. Rev. Neurosci. 24 [2001] 1 Orbito- frontal cortex
  7. 7. • Principles of Behavior Dynamics A C B Prefrontal Cortex How does a behavior become an addiction? BB B BAddiction behavior expressed dopamine Orbito- frontal cortex
  8. 8. Prolonged Drug Use Changes the Brain and In Fundamental and Long-Lasting Ways We Have Generated A Lot of Evidence Showing That…
  9. 9. We Have Evidence That These Changes Can Be Both Structural and Functional AND…
  10. 10. Positron Emission Tomography BRAIN IMAGING Magnetic Resonance Imaging
  11. 11. control cocaine abuser Decreases in Metabolism in Orbito Frontal Cortex (OFC) Volkow et al. Am. J. Psychiatry 148, 621
  12. 12. Source: McCann U.D. et al., The Journal of Neuroscience, 18(20), pp. 8417-8422, October 15, 1998. METH Suppresses Expression of DAT (note: duration of use/3-20 yrs; abstinent/ 1-4 yrs)
  13. 13. Implication: Brain changes resulting from prolonged use of psychostimulants, such as methamphetamine may be reflected in compromised cognitive and motor functioning.
  14. 14. Reward System in Addiction Cocaine Food METH Alcohol Ability to Experience Rewards Is Damaged treated More Less
  15. 15. Get Rewired by Drug Use Their Brains…
  16. 16. INHERITED FACTORS (genetic vulnerability-not inevitability) • Common strategy to investigate are Twin Studies
  17. 17. 17 22 r-SA r-candidate 5 6 3 samples, > 2 labs 4 samples, > 3 labs >2 samples, >2 labs Chromosomal Locations for Substance Abuse Vulnerability Loci Uhl et al Tr Genetics, updated June 03
  18. 18. VULNERABILITY to What? Starting Drug Use? Liking Drugs More? Continuing Drug Use? Becoming Addicted? Specific to A Particular Drug?

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