Outline5REVISED - THE SHADED PORTION OF THIS OUTLINE IS...

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1 THE SHADED PORTION OF THIS OUTLINE IS MATERIAL THAT WAS NOT COVERED IN CLASS AND WHICH WILL NOT BE ON THE TEST Outline 5: Drugs - Mechanisms of Action I. Some Basic Concepts and Definitions Drugs - What is a drug? Psychoactive Drugs -any chemical substance that alters mood or behavior as a result of alterations in the functioning of the brain Tolerance -decreased sensitivity to the effects of a drug as a result of exposure -Tolerance can be represented as a shift in the dose response curve - There are many neuronal and other mechanisms for tolerance - Tolerance effects include those resulting from increased breakdown of the drug and from neuronal adaptation to the drug effects -Conditioned drug tolerance and situationally specific tolerance Sensitization - increased sensitivity to the effects of a drug as a result of exposure - a given drug may have some effects to which an individual develops a tolerance and other effects to which the individual develops a sensitization. Withdrawal Syndromes - typically effects opposite to those produced by the drug Addiction (one definition) - habitual drug use with adverse social and/or health effects that resists attempts to stop the drug use Physical dependenc y - the onset of withdrawal syndromes upon removal of the drug The mesolimbic dopamine system (AKA - mesotelencephalic DA system)- is often implicated as the basis of many of the rewarding aspects of drugs that are taken recreationally and that are abused This system originates in nuclei in the hypothalamus. Bundles of neurons here project to the ventral tegmental area (VTA). Dopamine releasing neurons in the VTA project to the nucleus accumbens , septum and prefrontal cortex.
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2 The nucleus accumbens especially has been implicated in the reinforcing properties of some drugs. II. Overview of Synaptic Mechanisms of Drug Action A. Drugs can be: Agonists - drugs which mimic or enhance the effects of a neurotransmitter Antagonists - drugs which reduce or block the effects of a n neurotransmitter B. Drug Effects on Synaptic Transmission- Drugs can influence -neurotransmitter synthesis -neurotransmitter release -receptor binding
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3 -receptor activation -neurotransmitter reuptake -neurotransmitter breakdown Drugs can also influence -cellular metabolism -numbers of receptors -efficacy of receptors -gene expression
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