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Chapter Four

Chapter Four. Psychopharmacology Version Dated 21 Sep 2009. Chapter 4 Psychopharmacology. Neurotransmitters, Neuromodulators, and Neurohormones. Identifying Neurotransmitters Must be synthesized within the neuron

andrew-slater
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Chapter Four

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  1. Chapter Four Psychopharmacology Version Dated 21 Sep 2009

  2. Chapter 4Psychopharmacology

  3. Neurotransmitters, Neuromodulators, and Neurohormones • Identifying Neurotransmitters • Must be synthesized within the neuron • In response to an action potential, the substance is released in sufficient quantities to produce an effect in the postsynaptic cell • We should be able to duplicate the action of a suspected neurotransmitter experimentally on a postsynaptic cell • Some mechanism exists that ends the interaction between the neurotransmitter and the postsynaptic cell

  4. Figure 4.2 Major Categories of Neurotransmitters, Neuromodulators, and Neurohormones

  5. Neurotransmitters • Types of Neurotransmitters • Small molecule transmitters – meet all or most of criteria and play a vital role in neurotransmission • Neuropeptides – at least 40 act as neurotransmitters, neuromodulators, and neurohormones • Gaseous neurotransmitters – some gases transfer information from one cell to another

  6. Table 4.1 Features of Small-Molecule Transmitters and Neuropeptides

  7. Figure 4.3 The Distribution of Cholinergic Systems in the Brain

  8. Figure 4.4 Catecholamines Share a Common Synthesis Pathway

  9. Figure 4.5 Dopaminergic Systems in the Brain

  10. Figure 4.6 Noradrenergic Systems in the Brain

  11. Figure 4.8 The Distribution of Serotonergic Pathways in the Brain

  12. Figure 4.9 The NMDA Glutamate Receptor

  13. Figure 4.10 The GABAA Receptor Interacts with Several Drugs

  14. Figure 4.11 Distribution of Opiate Receptors in the Human Brain

  15. Drug Actions at the Synapse • Agonists enhance the activity of a neurotransmitter • Antagonists reduce the activity of a neurotransmitter

  16. Drug Actions at the Synapse • Neurotransmitter Production • Manipulating the synthesis of a neurotransmitter will affect the amount available for release • Neurotransmitter Storage • Interfering with the storage of a neurotransmitters in vesicles within a neuron • Neurotransmitter Release • Drugs can modify the release of a neurotransmitter in response to the arrival of an action potential

  17. Drug Actions at the Synapse • Receptor Effects • Can mimic the action of a neurotransmitter at the site • Can block the synaptic activity by occupying a binding site • Can influence the activity of the receptor • Reuptake Effects and Enzymatic Degradation • Deactivation of neurotransmitters

  18. Figure 4.12 Drug Interactions at the Cholinergic Synapse

  19. Figure 4.14 Drug Interactions at the Dopaminergic Synapse

  20. Figure 4.15 Drug Interactions at the Serotonergic Synapse

  21. Basic Principles of Drug Effects • Administration of Drugs • Method of administration leads to different effects on nervous system • Blood-brain barrier • Individual Differences • Drug effects influenced by body weight, gender, and genetics • Placebo Effects • User expectations influence drug effects • Double-blind experiment

  22. Figure 4.16 Concentration of a Drug in the Blood Supply Depends on the Method of Administration

  23. Basic Principles of Drug Effects • Tolerance and Withdrawal • Tolerance = lessened effects as a result of repeated administration • Withdrawal = occurs when substance use is discontinued; opposite of the effects caused by the discontinued drug • Addiction • Compulsive need to use the drug repeatedly • Causes of addiction • Treatment of addiction

  24. Figure 4.17 Tolerance and Withdrawal Can Result from Compensation

  25. Figure 4.18 The Nucleus Accumbens Participates in Reward and Addiction

  26. Effects of Psychoactive Drugs • Stimulants – increase alertness and mobility • Caffeine – antagonist for adenosine • Nicotine – agonist at the nicotinic cholinergic receptor • Cocaine and Amphetamine • Cocaine – dopamine reuptake inhibitor • Amphetamine – stimulates dopamine and norepinephrine release and inhibits their reuptake • Club Drugs: Ecstasy and GHB • MDMA – stimulates release of serotonin and oxytocin; toxic to serotonergic neurons • GHB – mimics inhibitory effects of GABA

  27. MDMA Ecstasy Destroys Serotonergic Neurons

  28. Figure 4.20 Caffeine Content of Common Products

  29. Effects of Psychoactive Drugs • Opiates • Synthesized from sap of opium poppy • Morphine, codeine, heroin • Endorphin receptors • Marijuana • THC – agonist at receptors for endogenous cannabinoids • Cannabinoid receptors in the hippocampus and prefrontal cortex

  30. Effects of Psychoactive Drugs • Other hallucinogens – have the ability to produce false perceptions • Mushrooms – agonist for GABA and glutamate • Mescaline – acts on serotonergic neurons • Phencyclidine (PCP) – antagonist at the NMDA glutamate receptor • LSD – serotonergic agonist

  31. Effects of Psychoactive Drugs • Alcohol • Agonist at the GABAA receptor • Stimulates dopaminergic reward pathways • Damaging effects on health • St. John’s Wort • Effective for mild depression • Interactions with other drugs

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