Handout - Lecture_12_-_Reward_and_addiction

Handout - Lecture_12_-_Reward_and_addiction - Motivation,...

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Unformatted text preview: Motivation, Operant conditioning PRESENT STIMULUS REMOVE STIMULUS BEHAVIOR INCREASES Positive Reinforcement Negative Reinforcement BEHAVIOR DECREASE S Punishment Extinction A Skinner box Intra-cranial self-stimulation (ICSS) Brain Reward Systems Self-stimulation- Olds & Milner, 1954- medial forebrain bundle - fibers running through the basal forebrain and lateral hypothalamus Why does reward circuitry exist? Primitive neural structures that give rise to reward circuitry Critical systems include those neural structures involved in mediating motivated behaviors and emotion (e.g., limbic structures) The Role of Dopamine in Reward Systems Mesolimbic pathway comprised of cells emanating from VTA and terminating in nucleus accumbens Dopamine antagonists suppress ICSS rates Permanent lesions suppress ICSS rates Extracellular Dopamine in Nucleus Hernandez & Hoebel, Life Sci. 42: 1705- 1712 D o p a m i n e % of the first sam ple 70 100 130 160 50 100 150 200 M inutes No Food Food Available Dopamine Involvement in Reward Systems Dopamine agonists are self-administered systemically and directly into brain Animals will work to terminate dopamine antagonist administration and humans report them to be dysphoric Lesioning mesolimbic dopamine neurons disrupts motivated behaviors Dopamine Involvement in Reward Systems High doses of dopamine antagonists decrease self-administration of several drugs of abuse. Destruction of dopamine systems leads to reduction or extinction of drug self-administration So maybe drugs of abuse are reinforcing/addictive because they hijack natural reward systems Click to edit Master subtitle style 1/5/11 Drug effects and drugs reward Understanding Drug Effects Drug Tissue e.g. stomach Blood (central) Brain & spinal cord (peripheral) Organs, metabolism Understanding Drug Effects Pharmacokinetics- Drug levels at target neural tissue will depend on - Route of administration- Level of concentration Relationship between route of delivery and Understanding Drug Effects Pharmacokinetics- Drug levels at target neural tissue will depend on - Route of administration- Absorption- E.g., Nicotine- acidity decreases buccal nicotine absorption Understanding Drug Effects Pharmacokinetics- Drug levels at target neural tissue will depend on - Route of administration- Absorption- Distribution- E.g., blood brain barrier (heroin vs. morphine)- Heroin has a higher abuse potential because it can pass the blood brain barrier easier and once it is in the brain it transforms into morphine. (metabolic pathway) Understanding Drug Effects Pharmacokinetics- Drug levels at target neural tissue will depend on - Route of administration- Absorption- Distribution- Elimination- Metabolism- Excretion Understanding Drug Effects...
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This note was uploaded on 01/05/2011 for the course PSY 10994 taught by Professor Ericdonny during the Spring '08 term at Pittsburgh.

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Handout - Lecture_12_-_Reward_and_addiction - Motivation,...

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