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39.1: Introduction to Psychopharmacology

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    Psychopharmacology is the study of how drugs affect behavior. If a drug changes your perception, or the way you feel or think, the drug exerts effects on your brain and nervous system. We call drugs that change the way you think or feel psychoactive or psychotropic drugs, and almost every- one has used a psychoactive drug at some point (yes, caffeine counts). Understanding some of the basics about psycho- pharmacology can help us better understand a wide range of things that interest psychologists and others. For example, the pharmacological treatment of certain neurodegenerative diseases such as Parkinson’s disease tells us something about the disease itself. The pharmacological treatments used to treat psychiatric conditions such as schizophrenia or depression have undergone amazing development since the 1950s, and the drugs used to treat these disorders tell us something about what is happening in the brain of individuals with these conditions. Finally, understanding something about the actions of drugs of abuse and their routes of administration can help us understand why some psychoactive drugs are so addictive. In this module, we will provide an overview of some of these topics and discuss some current controversial areas in the field of psychopharmacology.

    Behaviorism_1.gif
    Figure \(\PageIndex{1}\): Drugs that alter our feelings and behavior do so by affecting the communication between neurons in the brain. [“SUBNET Final 1” by DARPA is in the public domain.]

    Psychopharmacology, the study of how drugs affect the brain and behavior, is a relatively new science, although people have probably been taking drugs to change how they feel from early in human history (consider the practice of eating fermented fruit, mixing up ancient beer recipes, and chewing on the leaves of the cocaine plant for stimulant properties as just some examples). The word psychopharmacology itself tells us that this is a field that bridges our understanding of behavior (and brain) and pharmacology, and the range of topics included within this field is extremely broad.

    Virtually any drug that changes the way you feel does this by altering how neurons communicate with each other. Neurons (more than 100 billion in your nervous system) communicate with each other by releasing a chemical (a neurotransmitter) across a tiny space between two neurons (the synapse). When the neurotransmitter crosses the synapse, it binds to a postsynaptic receptor (protein) on the receiving neuron and the message may then be transmitted onward. Obviously, neurotransmission is far more complicated than this, but the first step is understanding that virtually all psychoactive drugs interfere with or alter how neurons communicate with each other.

    There are many neurotransmitters. Some of the most important in terms of psychopharmacological treatment and drugs of abuse are outlined in Table \(\PageIndex{1}\). The neurons that release these neurotransmitters, for the most part, are localized within specific circuits of the brain that mediate these behaviors. Psychoactive drugs can either increase activity at the synapse (these are called agonists) or reduce activity at the synapse (antagonists). Different drugs do this by different mechanisms, and some examples of agonists and antagonists are presented in Table \(\PageIndex{2}\). For each example, the drug’s trade name, which is the name of the drug provided by the drug company, and generic name (in parentheses) are provided.

    Table \(\PageIndex{1}\):Neurotransmitters and Their Related Behaviors or Diseases

    Neurotransmitter

    Abbreviation

    Behaviors or Diseases Related to These Neurotransmitters

    Acetylcholine

    Ach

    Learning and memory; Alzheimer’s disease; muscle movement in the peripheral nervous system

    Dopamine

    DA

    Reward circuits; motor circuits involved in Parkinson’s disease; schizophrenia

    Norepinephrine

    NE

    Arousal; depression

    Serotonin

    5HT

    Depression; aggression; schizophrenia

    Glutamate

    GLU

    Learning; major excitatory neurotransmitter in the brain

    GABA

    GABA

    Anxiety disorders; epilepsy; major inhibitory neurotransmitter in the brain

    Endogenous opioids

    Endorphins, enkephalins

    Pain; analgesia; reward

    Table \(\PageIndex{2}\) provides examples of drugs and their primary mechanisms of action, but it is very important to realize that drugs also have effects on other neurotransmitters. This contributes to the kinds of side effects that are observed when someone takes a particular drug. The reality is that no drugs currently available work only exactly where we would like in the brain or only on a specific neurotransmitter. In many cases, individuals are sometimes prescribed one psychotropic drug but then may also have to take additional drugs to reduce the side effects caused by the initial drug. Sometimes individuals stop taking medication because the side effects can be so profound.

    Table \(\PageIndex{2}\):Drugs and Their Primary Mechanisms of Action and Uses

    Drug

    Mechanism of Action

    Use

    Agonist/Antagonist

    l-dopa

    Increases synthesis of DA

    Parkinson’s disease

    Agonist for DA

    Adderall (mixed salt amphetamine)

    Increases release of DA, NE

    ADHD

    Agonist for DA, NE

    Ritalin (methylphenidate)

    Blocks removal of DA, NE, and lesser (5HT) from synapse

     

    ADHD

    Agonist for DA, NE mostly

    Aricept (donepezil)

    Blocks removal of Ach from synapse

    Alzheimer’s disease

    Agonist for Ach

    Prozac (fluoxetine)

    Blocks removal of 5HT from synapse

    Depression, obsessive compulsive disorder

    Agonist for 5HT

    Seroquel (quetiapine)

    Blocks DA and 5HT receptors

    Schizophrenia, bipolar disorder

    Agonist for DA, 5HT

    Revia (naltrexone)

    Blocks opioid postsynaptic receptors

    Alcoholism, opioid addiction

    Antagonist (for opioids)

     


    39.1: Introduction to Psychopharmacology is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.

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