BIOMED SCIE Lecture 23 ADDICTION

• Brain reward system


  Primarily modulated by dopamine, a major neurotransmitter
• Drugs of abuse


  Activate the brain reward system through various input pathways, leading to feelings of pleasure or relief from stress and emotional pain
• Activation of the brain reward system by drugs of abuse


  Akin to the natural rewarding responses associated with behaviors like eating, drinking, and sex, increasing the likelihood of repeated drug use due to positive reinforcement
• Cocaine and MDMA


  Induce unnatural highs in dopamine levels
• Cocaine mechanism


  1. Derived from the coca plant, acts by blocking neurotransmitter recycling, resulting in an abnormal accumulation of dopamine

  2. Accumulation triggers enhanced receptor activation

  3. Changes in gene activity and brain circuitry, ultimately contributing to drug dependence and addiction
• Cocaine use


  • Produces a short-lived "high" characterized by euphoria and increased energy
  • Followed by adverse effects like dizziness, headaches, and anxiety during the "low" phase
  • Long-term effects include loss of concentration, memory problems, paranoia, and reduced interest in sex
• MDMA (ecstasy)


  • Primarily targets serotonin transporters, inhibiting neurotransmitter recycling and causing serotonin release into the synaptic cleft
  • Leads to acute effects such as hyperactivity, euphoria, and emotional openness, but also visual hallucinations and paranoid delusions
  • Acute toxicity can result in hyperthermia, a major complication
• Co-administration of caffeine with MDMA


  Exacerbates acute toxicity, increasing hyperthermia and heart rate
• Long-term effects of MDMA abuse


  • Depletion of neurotransmitter stores, leading to depression, anxiety, and nerve damage which may last for months to years
• Animal studies play a crucial role in understanding addiction mechanisms
• Mice more sensitive to cocaine provide insights into target molecules and neuronal pathways involved in addiction
• Research aims to identify ways to manipulate these targets and pathways to prevent and treat addiction and mitigate neurotoxic effects of drugs on the brain