1. Prepared by Jeffrey W. Grimm Western Washington University
PowerPoint Presentation for Biopsychology, 9th Edition by John P.J. Pinel
Prepared by Jeffrey W. Grimm
Western Washington University
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2. Chemicals That Harm with Pleasure
Chapter 15
Drug Addiction and the
Brain’s Reward Circuits
Chemicals That Harm with Pleasure
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3. Basic Principles of Drug Action
Psychoactive drugs: drugs that influence subjective experience and behavior by acting on the nervous system
Drug administration: route of administration influences the rate at which and the degree to which the drug reaches its site of action.
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4. Drug Administration and Absorption
Ingestion: oral route
Easy and relatively safe
Absorption via digestive tract is unpredictable.
Injection: bypasses digestive tract
Subcutaneously (SC): under the skin
Intramuscular: into large muscles
Intravenously (IV): into veins; drug delivered directly to brain
Inhalation: Tobacco and Marijuana
Absorbed through capillaries in lungs
Absorption through Mucous Membranes
Nose, mouth, rectum
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5. Mechanisms of Drug Action
In order for a psychoactive drug to have an effect, it must get to the brain; it must pass through the blood–brain barrier.
The actions of most drugs are terminated by enzymes in the liver: drug metabolism.
Small amounts may also be excreted in urine, sweat, feces, breath, and mother’s milk.
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Drug Tolerance
Drug tolerance is decreased sensitivity to a drug as a consequence of exposure to it.
Cross tolerance: exposure to one drug can produce tolerance to similar drugs.
Example: alcohol and benzodiazepines
Tolerance often develops to some effects and not others.
Functional
Decreased responsiveness at the site of action, fewer receptors, decreased efficiency of binding at receptors, receptors less responsive
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7. Drug Withdrawal Effects and Physical Dependence
Seen When Drug Use Is Terminated
Withdrawal symptoms are the opposite of the drug’s effects.
The body has made changes to compensate for the drug’s presence and functions normally with the drug present.
Severity of withdrawal varies according to the drug and the pattern of use.
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Addiction: What Is It?
“Addicts” are those who continue to use a drug despite its adverse effects on health and social life.
Addiction and physical dependence may occur together or separately.
After withdrawal symptoms due to physical dependence have subsided, addicts may still crave the drug.
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9. Five Commonly Abused Drugs
Tobacco
Alcohol
Marijuana
Cocaine
Opiates
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Tobacco
Nicotine: tobacco’s major psychoactive ingredient
About 70 percent of those who experiment with smoking become addicted.
Only about 20 percent of attempts to quit are successful.
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11. Effects of Long-Term Tobacco Use
Smoker’s syndrome: chest pain, labored breathing, wheezing, coughing, increased susceptibility to respiratory infections
Smokers are susceptible to various lethal lung disorders: pneumonia, bronchitis, emphysema, and lung cancer.
Quitting smoking typically results in major health benefits.
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Alcohol
A Depressant
Heritability estimate for alcohol addiction is about 50 percent.
Metabolic and functional tolerance develops.
Alcohol affects almost every tissue in the body.
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13. Effects of Chronic Alcohol Consumption
Severe Withdrawal in Three Phases
5–6 hours after quitting drinking: tremors, nausea, sweating, vomiting, etc.
15–30 hours after quitting drinking: convulsive activity
24–48 hours after quitting drinking: delirium tremens; this may last 3–4 days.
Korsakoff’s Syndrome
Cirrhosis
Fetal alcohol syndrome affects children of mothers who are heavy alcohol users during pregnancy.
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Marijuana
Cannabis sativa: common hemp plant
THC is marijuana’s primary psychoactive constituent, although over 80 others are present.
Endogenous transmitter is anandamide.
High doses impair short-term memory and interfere with tasks involving multiple steps.
Addiction potential is low.
Negative effects of long-term use are far less severe than those associated with alcohol and tobacco.
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15. Adverse Effects of Heavy Marijuana Use
Respiratory Problems Such as Cough, Bronchitis, Asthma
Single large doses can trigger heart attacks in susceptible individuals.
There is no evidence that marijuana causes permanent brain damage.
There is a possible correlation between marijuana use and schizophrenia, but no causal link has been shown.
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16. Medicinal Uses of Marijuana
Treats Nausea
Blocks Seizures
Dilates Bronchioles of Asthmatics
Decreases Severity of Glaucoma
Reduces Some Forms of Pain
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17. Cocaine and Other Stimulants
Stimulants increase neural and behavioral activity.
Cocaine and its derivatives are commonly abused.
Crack is a potent, cheap, and smokeable form of cocaine.
Cocaine is an effective local anesthetic.
Synthetic analogues procaine and lidocaine are used today.
Cocaine binges or sprees may lead to cocaine psychosis.
Looks like paranoid schizophrenia
While tolerance may develop to some effects of cocaine, sensitization is seen to motor and convulsive effects.
Although cocaine is highly addictive, withdrawal is relatively mild.
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Other Stimulants
Amphetamine (“Speed”)
Effects like cocaine; can produce psychosis
MDMA (“Ecstasy”)
Impairs dopaminergic and serotonergic function in animal studies; human relevance unclear
Impairs executive function, inhibitory control, and decision making (as shown by cortex and limbic functional brain scan abnormalities)
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19. Opiates: Heroin and Morphine
Morphine and codeine are obtained from the opium poppy.
Opiates: these drugs and others with similar structures or effects
Medicinal Uses
Analgesics (painkillers)
Treatment of cough and diarrhea
High Risk of Addiction
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Opiate Addiction
Addicts are drawn to use by the rush following IV injection.
Tolerance and physical dependence develop.
The desire to avoid withdrawal adds to an addict’s motivation to use.
Although opiates are highly addictive, direct health hazards are relatively minor.
There are many health hazards related to the use of needles.
The severity of opiate withdrawal has been exaggerated.
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21. Treatment for Heroin Addiction
Methadone binds to opiate receptors.
Produces less pleasure
Administered orally
Prevents withdrawal
Buprenorphine: similar to methadone but longer lasting
Substituting a Less Dangerous Drug for the Abused Drug
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Comparison of the Hazards of Tobacco, Alcohol, Marijuana, Cocaine, and Heroin
Alcohol and tobacco are associated with the greatest negative impact on public health.
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