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Case Study#2: Effect of Alcohol/Drugs on Teen Brain

Case Study#2: Effect of Alcohol/Drugs on Teen Brain. Yehuda Ben-Shahar, PhD Department of Biology, Washington University in St. Louis. Drosophila melanogaster. Courtship as a model for social behaviors. Drug use in teenagers – what does it do to their brains?.

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Case Study#2: Effect of Alcohol/Drugs on Teen Brain

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  1. Case Study#2: Effect of Alcohol/Drugs on Teen Brain Yehuda Ben-Shahar, PhD Department of Biology, Washington University in St. Louis

  2. Drosophila melanogaster

  3. Courtship as a model for social behaviors

  4. Drug use in teenagers – what does it do to their brains? Short-term versus long-term effects of use of, and addiction to drugs

  5. Heritability • Huntington’s disease = 100% • Sickle Cell Anemia = 100% • Obesity = 60%-90% • Breast Cancer = 30% • Asthma = 25% • Type II Diabetes = 26% • Alcohol dependence = 38%-64% • Nicotine dependence = 75% But… the environment is a key factor as well!

  6. Why should we care? Data from the NIDA InfoFacts: High School and Youth Trends

  7. Drugs – mode of action Most known drugs affect neurotransmission in the brain – typically by acting on specific receptors

  8. Alcohol, Barbiturates, and Benzodiazepines These drugs exert their effects mostly via the gamma-Aminobutyric acid (GABA) signaling pathway GABA is the principle inhibitory neurotransmitter in the mammalian brain

  9. Alcohol, Barbiturates, and Benzodiazepines Short-term effects • Potentiates GABA-activated Cl- channels • Allows more Cl- to cross the membrane • Increases inhibition in the post-synaptic cell • Increases turnover of norepinephrine and dopamine, • Decreases transmission in acetylcholine systems • Increases production of beta-endorphin in the hypothalamus.

  10. Alcohol, Barbiturates, and Benzodiazepines Long-term effects • Damage to the frontal lobes of the brain • An overall reduction in brain size • Increase in the size of the ventricles • Alcoholism can cause Vitamin B-1 (thiamine) deficiency, leading to Wernicke-Korsakoff syndrome, characterized by amnesia, apathy and disorientation. Embryonic rat brain

  11. Alcohol Dependence Use of alcohol despite severe social or physical consequences. Characterized by (some or all of the following): • Tolerance • Withdrawal • Uncontrollable use • Social, occupational, recreational consequences • Use continued despite knowledge of alcohol-related harm

  12. Genetics of Alcohol Dependence • First behavioral disorder to have a validated genetic finding • Subjects of Asian descent noted to have facial flushing and decreased tolerance compared to subjects of European descent • 1980 – Found 50% of Japanese post-mortem liver extracts were missing aldehyde dehydrogenase (ALDH) isozyme I

  13. ALDH isozyme I deficiency Elevated ethanal (acetaldehyde) levels cause • Facial flushing • Nausea • Tachycardia • Causes behavioral aversion to alcohol • 1/3 susceptibility to alcoholism as compared to wild-type • Mechanism of disulfiram (Antabuse)

  14. Marijuana

  15. Marijuana Short-term effects • Delta-9 tetrahydrocannabinol or "THC” binds to cannabinoid receptors, which exist in many areas of the brain • Affects the levels of norepinephrine, dopamine, serotonin, and GABA in the brain • Relaxation • Reduced coordination • Reduced blood pressure • Sleepiness • Disruption in attention • An altered sense of time and space

  16. Marijuana Long-term effects • Whether marijuana usage leads to addiction or long-term mental abnormalities is still controversial and a topic of current research • Data suggest that onset of schizophrenia in susceptible individuals is associated with cannabis use • Because marijuana contains many other chemicals that are also inhaled, it leads similar respiratory problems as smoking cigarettes, as well as cancer and immune deficiencies

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