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CHAPTER 5

CHAPTER 5. Drugs, Addiction, and Reward Psychoactive Drugs. Psychoactive Drugs. Drug : a substance that on entering the body changes the body or its functioning. An agonist mimics or enhances the effect of a neurotransmitter.

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CHAPTER 5

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  1. CHAPTER 5 Drugs, Addiction, and Reward Psychoactive Drugs

  2. Psychoactive Drugs • Drug : a substance that on entering the body changes the body or its functioning. • An agonist mimics or enhances the effect of a neurotransmitter. • An antagonist may occupy the receptors without activating them, simultaneously blocking the transmitter from binding to the receptors. • Psychoactive drugs are those that have psychological effects, such as anxiety relief or hallucinations.

  3. Psychoactive Drugs • Addiction: • preoccupation with obtaining a drug • compulsive use of the drug in spite of adverse consequences • high tendency to relapse after quitting • Typically defined as an individual showing both withdrawal and tolerance. • Withdrawal: • negative reaction that occurs when drug use is stopped • Body’s compensatory reaction. • Tolerance: • individual becomes less responsive to the drug • requires increasing amounts of the drug to produce the same results.

  4. Psychoactive Drugs: opiates • Opiates • derived form the opium poppy. • Can also be synthetically made • Act on opiate receptors or endorphin receptors • Several important effects: • analgesic (pain relieving) • hypnotic (sleep inducing) • produce a strong euphoria (sense of happiness of ecstasy). • Types of opiates: • Morphine: pain relief, surgical pain relief, cancer • Derivatives include codeine, vicodin, oxycotin, etc... • Heroin • synthesized from morphine • marketed as an over-the-counter analgesic until its dangers were recognized • now it is an illegal drug in the U.S.

  5. Opiate drug action • Endorphins: • body produces its own natural opiates, which are neuromodulators • Released when in pain, motor exertion, stress • Endogenous opiates: • Endogenous = made by the body. • Opiate drugs are effective because they mimic endorphins • Because of CNS effects and cognitive effects, very high likelihood of abuse.

  6. Psychoactive drugs: the depressants • Depressants: • drugs that reduce central nervous system activity. • Sedatives: calming drugs • Barbiturates including amobarbital (Amytal); pentobarbital (Nembutal); secobarbital (Seconal) and Phenobarbitol (Luminal) • Anxiolytic: anxiety-reducing drugs: • Benzodiazepines ("minor tranquilizers") including • Klonopin; diazepam (Valium); estazolam (Prosom); flunitrazepam (Rohypnol) ; lorazepam (Ativan) ; midazolam (Versed); nitrazepam (Mogadon) ; oxazepam (Serax) ; triazolam (Halcion); ;ttemazepam (Restoril; , Normison, Planum; Tenox, Temaze) ; chlordiazepoxide (Librium)

  7. Psychoactive drugs: the depressants • Hypnotic drugs: induce sleep-like states: • Nonbenzodiazepines: Zolpidem; Zaleplon; Zopiclone; Eszopiclone • Antihistamines: Diphenhydramine (Benadryl); Doxylamine; Hydroxyzine; Promethazine • Others: • gamma-hydroxybutyric acid (Xyrem) ; Glutethimide • Chloral hydrate • EthchlorvynolLevomepromazine; Chlormethiazole

  8. Sedative effects on cns • Barbiturates • Suppress inhibitory centers • in small amounts: act selectively on higher cortical centers, especially those involved in inhibiting behavior • In low doses :produce talkativeness, increased social interaction, • Higher doses: sedatives and hypnotics. • Barbiturates do not reduce pain, but they do reduce the anxiety associated with pain. • Barbiturates produce their effects by decreasing glutamate activity and increasing GABA activity. • They operate at the barbiturate receptor on the GABAA complex.

  9. Benzodiazepines- an alternative to barbiturates? • A few decades ago: • Barbiturates = drug of choice for treating anxiety • Also as most common drug for situations requiring sedation. • BUT: high liability potential for addiction and high rate of accidental or intentional death. • Benzodiazepines: largelyreplaced barbiturates • produce anxiety reduction, • Also induce sedation and muscle relaxation. • operate at the benzodiazepine receptor on the GABAA complex. • At first, thought non-addictive • Today know that are highly addictive

  10. Psychoactive drugs: Alcohol • Ethanol, or alcohol: • is a drug • fermented from fruits, grains, and other plant products. • Is a DEPRESSANT • It acts at many brain sites to produce euphoria, anxiety reduction, sedation, poor motor coordination, and cognitive impairment • Why is it a depressant? • Depresses CNS • Inhibits areas of the brain that inhibit acting out, inappropriate behavior, etc..

  11. How does alcohol affect the CNS? • Alcohol inhibits the release of glutamate (the most prevalent excitatory neurotransmitter). • Glutamate reduction produces a sedating effect; • Chronic use results in a compensatory increase in the number of glutamate receptors, • This increase probably accounts for the seizures that sometimes occur during withdrawal.

  12. How does alcohol affect the CNS? • Alcohol also increases the release of gamma-aminobutyric acid (GABA; • the most prevalent inhibitory neurotransmitter). • Alcohol specifically affects the A subtype of GABA receptor. • The combined effect at these two receptors is: • sedation, • anxiety reduction, • muscle relaxation, • inhibition of cognitive and motor skills.

  13. Alcohol abuse effects • Cirrhosis of the liver, • Common side effect of chronic alcoholism • in its severest form is fatal. • Vitamin B1 deficiency • associated with chronic alcoholism • can produce brain damage and Korsakoff’s syndrome

  14. Alcohol abuse effects • Korsakoff’s syndrome • Neurological syndrome due to alcohol damage, B1 deficiency • involves severe memory loss along with sensory and motor impairment. • Alcohol withdrawal symptoms • involves tremors, anxiety, and mood and sleep disturbances; • Delirium tremors • more severe reactions • hallucinations, delusions, confusion, and in extreme cases, seizures • possible death.

  15. Why are Psychoactive Drugs “bad”? • Do tell us a great deal about brain functioning! • BUT: pattern of effect they produce is usually unlike normal functioning. • Drugs are wide acting: • affect wide areas of the brain indiscriminately • normal activation tends to be more discrete and localized • Can’t control drug effects • Not act only in ways you want them to. • May overstimulate, “burn out” neurons • May result in long term damage to system

  16. Addiction • Agonist treatments replace an addicting drug with another drug that has a similar effect. • Opiate addiction is often treated with a synthetic opiate called methadone. • Antagonist treatments involve drugs that block the effects of the addicting drugs. • Drugs that block opiate receptors are used to treat opiate addictions and alcoholism because they reduce the pleasurable effects of the drug. • Another experimental strategy is to interfere with the dopamine reward system. • Baclofen reduces dopamine activity in the ventral tegmental area by activating GABAB receptors on dopaminergic neurons.

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