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Mechanisms of Drug Action

Mechanisms of Drug Action. Drug Agonists Mimic or enhance the activity of a neurotransmitter. ...Mechanisms of Drug Action. Drug Antagonists Block the activity of a neurotransmitter False Transmitter. Effects of Drug Use. Addiction Tolerance Withdrawal

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Mechanisms of Drug Action

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  1. Mechanisms of Drug Action • Drug Agonists • Mimic or enhance the activity of a neurotransmitter

  2. ...Mechanisms of Drug Action • Drug Antagonists • Block the activity of a neurotransmitter • False Transmitter

  3. Effects of Drug Use • Addiction • Tolerance • Withdrawal • Dependence-physical vs. psychological

  4. Classes of Psychoactive Drugs • Narcotics • Depressants • Stimulants • Psychedelics

  5. Narcotics • Main effects- analgesia and sleepiness • Natural source: opium poppy • Semisynthetic: heroin • Synthetic: prescription painkillers

  6. Mechanism of Narcotic Action • Endorphin agonist

  7. Long-Term Effects • Tolerance develops rapidly • Severe withdrawal symptoms • Strong psychological dependence

  8. Depressants • Act on central nervous system (CNS) • Reduce anxiety and induce drowsiness • Types: Alcohol and Sedative-hypnotics

  9. Alcohol • Ethyl alcohol • comes from fermented grains and fruits

  10. …Alcohol • Blood Alcohol Levels • Legal limit- .08 to .10

  11. Mechanism of Action • Depresses functioning of the reticular formation • Inhibits movement of Na+ into cell membrane • Increases effect of GABA on postsynaptic membrane • Increases effect of endorphin stimulation on opiate receptors

  12. Long-Term Effects • Tolerance • Withdrawal • Physical and psychological dependence

  13. Sedative-hypnotic drugs • Types • Barbiturates • Nonbarbiturates • Anti-anxiety • Antipsychotics

  14. Mechanismof Action • Depression of the CNS • Barbiturates and nonbarbiturates • Enhance the binding of GABA and increase action on the postsynaptic membrane • Anti-anxiety drugs • Attach to receptor sites and enhance the binding of GABA • Antipsychotic drugs • Block postsynaptic dopamine receptors • Impair the release of dopamine from presynaptic membrane

  15. Long-Term Effects • Tolerance • Withdrawal • Physical and psychological dependence • exception: antipsychotic drugs

  16. Stimulants • Activate sympathetic nervous system and reticular activating system

  17. Types of Stimulants • Amphetamines • Cocaine • Caffeine • Nicotine

  18. Mechanisms of Action • Amphetamines • Increase the release of norepinephrine and dopamine from presynaptic membrane and block reuptake of both • Cocaine • Stimulates noradrenergic and dopaminergic neurons by blocking reuptake of norepinephrine and dopamine • Caffeine • Blocks the release of adenosine, increasing activity of glutamate • Nicotine • Activates cholinergic (nicotinic) receptors and increases release of dopamine from presynaptic membrane

  19. … Mechanisms of Action • Caffeine • Blocks the release of adenosine, increasing activity of glutamate

  20. … Mechanisms of Action • Nicotine • Activates cholinergic (nicotinic) receptors and increases release of dopamine from presynaptic membrane

  21. Effects of Use • Tolerance develops quickly • Withdrawal ("crashing") • Physical and psychological dependence

  22. Psychedelics (Hallucinogens) • Alters sensory experience

  23. Types • Mescaline- derives from peyote cactus • Marijuana • Active ingredient THC • LSD and PCP- both synthetic drugs

  24. Mechanism of Action • LSD- serotonin agonist • THC- anandamide agonist

  25. Effects of Use • Unpredictability of effect • Flashbacks • Tolerance • Psychological dependence

  26. Addiction and Reinforcement • 1954- Olds and Milner's experiment with electrical brain stimulation

  27. Medial Forebrain Bundle (MFB) • Located in the limbic system • Reinforcing Effect of MFB Stimulation • Motivational Influence of MFB Stimulation • Influence of Reinforcers on MFB Function • Influence of Deprivation on the MFB

  28. Mesotelencephalic Reinforcement System • Tegmentostriatal pathway • Regulates the motivational properties of reinforcers

  29. ...Mesotelencephalic Reinforcement System • Nigrostriatal pathway • Memory consolidation

  30. Role of Dopamine in Reinforcement • Ventral Tegmental Area (VTA) • Nucleus Accumbens (NA) • Opiates

  31. Treatment of Heroin Addiction • Methadone- endorphin agonist

  32. … Treatment of Heroin Addiction • Naltrexone-opiate antagonist

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