Transcript Chapter 16 autism powerpoint Lecture Notes Page

Chapter 16
Drug Abuse
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Common Features of Addiction
 Physical versus Psychological Addiction
 Tolerance:
• The fact that increasingly large doses of drugs
must be taken to achieve a particular effect;
caused by compensatory mechanisms that
oppose the effect of the drug.
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Common Features of Addiction
 Physical versus Psychological Addiction
 Withdrawal symptoms:
• The appearance of symptoms opposite to those
produced by a drug when the drug is suddenly no
longer taken; caused by the presence of
compensatory mechanisms.
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Common Features of Addiction
 Positive Reinforcement
 Positive reinforcement:
• Addictive drugs have reinforcing effects. That is,
their effects include activation of the
reinforcement mechanism.
• This activation strengthens the response that
was just made, namely, taking the drug.
• Drugs with the most immediate effects tend to be
the most addictive.
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Common Features of Addiction
 Negative reinforcement
 Negative reinforcement:
• The removal or reduction of an aversive stimulus
that is contingent on a particular response, with
an attendant increase in the frequency of that
response.
• If taking a drug “turns off” aversive withdrawal
effects it is a negatively reinforced behavior that
will increase in frequency.
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Common Features of Addiction
 Craving and Relapse
 Craving:
• The desire to take a drug.
 Relapse:
• A return to the use of a drug following a period of
abstinence from use of the drug.
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Common Features of Addiction
 Craving and Relapse
 Brain mechanisms:
• Relapse appears to involve activation of the
mesolimbic system of dopaminergic neurons.
• Relapse caused by stimuli previously associated
with cocaine appears to involve the amygdala as
well as the mesolimbic dopamine system
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Common Features of Addiction
 Craving and Relapse
 Stress:
• Clinicians have long observed that stressful
situations can cause a former drug addict to
relapse.
• Stressful stimuli, even those that occur early in
life, increase an animal’s susceptibility to drug
addiction.
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Commonly Abused Drugs
 Opiates
 Cocaine and Amphetamines
 Nicotine
 Alcohol and Barbiturates
 Cannabis
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Common Features of Addiction
 Opiates:
• Opium is derived from a sticky resin produced by
the opium poppy and has been eaten or smoked
for centuries.
• Heroin is the most commonly abused opiate.
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Common Features of Addiction
 Neural Basis of Reinforcing Effects
 Opiate Administration:
• When an opiate is administered it stimulates
opiate receptors located on neurons in various
parts of the brain and cause a variety of effects
including:
Analgesia
Hypothermia
Sedation
Reinforcement
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Common Features of Addiction
 Neural Basis of Reinforcing Effects
 Periaqueductal gray matter (PAG):
• Stimulation of the PAG opiate receptors cause
analgesia.
 Preoptic area:
• Stimulation of the preoptic area opiate receptors
cause hypothermia (reduction of body
temperature).
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Common Features of Addiction
 Neural Basis of Reinforcing Effects
 Mesencephalic reticular formation:
• Stimulation of the opiate receptors in the
mesencephalic reticular formation cause
sedation.
 Ventral Tegmental area (VTA) and the nucleus
accumbens:
• Stimulation of the opiate receptors in the VTA and
nucleus accumbens play a role in the reinforcing
effects of opiates.
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Common Features of Addiction
 Cocaine and Amphetamine
• Cocaine and amphetamine have similar
behavioral effects, because both act as potent
dopamine agonists.
• The site of action of cocaine and amphetamine
are different.
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Common Features of Addiction
 Cocaine and Amphetamine
 Cocaine:
• Cocaine binds with and deactivates the
dopamine transporter proteins, thus blocking the
reuptake of dopamine after it is released by
terminal buttons, thus acting as a dopamine
agonist.
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Common Features of Addiction
 Cannabis
 Brain mechanisms:
• THC administration stimulates release of
dopamine in the nucleus accumbens and the
ventral tegmental area
• The drug appears to act directly on dopaminergic
terminal buttons-presumably on presynaptic
heteroreceptors.
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Copyright © Allyn & Bacon 2004
Common Features of Addiction
 Cocaine and Amphetamine
 Amphetamine:
• Amphetamine inhibits the reuptake of dopamine,
but its most important effects is to directly
stimulate the release of dopamine from terminal
buttons.
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Common Features of Addiction
 Cocaine and Amphetamine
 Effect of cocaine and amphetamine:
• The effects of cocaine and amphetamine seen in
people who abuse these drugs regularly include
psychotic behavior: hallucinations, delusions of
persecution (paranoid behavior), mood
disturbances, and repetitive motor behaviors.
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Common Features of Addiction
 Cocaine and Amphetamine
 Effect of cocaine and amphetamine:
• Prior abusers of methamphetamine showed a
decrease in the number of dopamine transporters
in the caudate nucleus and putamen, despite a
three year abstinence from the drug.
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Common Features of Addiction
 Cocaine and Amphetamine
 Effect of cocaine and amphetamine:
• Both drugs are potent dopamine agonists, these
drugs activate the mesolimbic system and
reinforce drug-taking behavior.
• Both drugs increase the concentration of
dopamine in the nucleus accumbens that is a
critical site in the reinforcing effect of the drugs.
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Common Features of Addiction
 Cocaine and Amphetamine
 Effect of cocaine and amphetamine:
• Long-term cocaine or amphetamine use does not
produce tolerance and is even likely to produce
sensitization to the effects of the drug.
• Withdrawal from cocaine does not cause physical
symptoms, but it does cause unpleasant feelings,
including dysphoria and decreased ability to feel
pleasure.
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Common Features of Addiction
 Nicotine
 Nicotine:
• Nicotine is an addictive drug and it accounts for
more deaths than the so-called “hard drugs”.
• The World Health Organization reported that onethird of the adult population of the world smokes.
• Investigators estimate that by the year 2020,
tobacco will be the largest single health problem
worldwide, with 8.4 million deaths per year.
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Common Features of Addiction
 Nicotine
 Nicotine:
• Forty percent of people continue to smoke after
having had a laryngectomy (which is usually
performed to treat throat cancer).
• More than 50 percent of heart attack survivors
continue to smoke, and about 50 percent of
people continue to smoke after submitting to
surgery for lung cancer.
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Common Features of Addiction
 Nicotine
 Nicotine:
• Nicotine stimulates acetylcholine receptors and
increases the activity of dopaminergic neurons of
the mesolimbic system, which contain these
receptors, and caused dopamine to be released
in the nucleus accumbens.
• Injections of a nicotine agonist into the ventral
tegmental area will reinforce a conditioned place
preference.
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Common Features of Addiction
 Alcohol and Barbiturates
 Alcohol:
• Alcohol has greater costs to society than any
other drug.
• A large percentage of deaths and injuries caused
by motor vehicle accidents are related to alcohol.
• The leading cause of mental retardation in the
Western world today is alcohol consumption by
pregnant women.
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Common Features of Addiction
 Alcohol and Barbiturates
 Sites of action:
• Alcohol has two primary sites of actions. It serves
as an indirect agonist at GABAA receptors and as
an indirect antagonist at NMDA receptors.
• Stimulation of both receptors systems triggers
apoptosis (cellular death).
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Common Features of Addiction
 Alcohol and Barbiturates
 Behavioral effects:
• At low doses alcohol produces mild euphoria and
has an anxiolytic effect (reduces anxiety).
• At higher doses alcohol produces uncoordination
and sedation.
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Common Features of Addiction
 Alcohol and Barbiturates
 Behavioral effects:
• The mild euphoria of alcohol provides positive
reinforcement for continued drinking.
• Alcohol also relieves anxiety and continued use
is negatively reinforced.
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Common Features of Addiction
 Alcohol and Barbiturates
 Brain mechanisms:
• Alcohol, like other addictive drugs, increases the
activity of the dopaminergic neurons of the
mesolimbic system and increases the release of
dopamine in the nucleus accumbens.
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Common Features of Addiction
 Alcohol and Barbiturates
 Brain mechanisms:
• Alcohol enhances the action of GABA and
GABAA receptors and interferes with the
transmission of glutamate at NMDA receptors.
• The perceptual effects of alcohol are mimicked
by both GABA agonists and NMDA antagonists.
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Common Features of Addiction
 Alcohol and Barbiturates
 Brain mechanisms:
• Observations strongly suggest that NMDA
receptors are responsible for the seizures
produced by alcohol withdrawal.
• The sedative effect of alcohol also appears to
exerted at the GABAA receptor.
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Common Features of Addiction
 Cannabis
 Cannabis:
• THC is the active ingredient in marijuana.
• The site of action is the endogenous cannabinoid
receptor in the brain, the CB1 receptor, has been
discovered, and the distribution of this receptor
has been mapped.
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Common Features of Addiction
 Cannabis
 Brain mechanisms:
• The hippocampus contains a large concentration
of THC receptors.
• Marijuana is known to affect people’s memory by
disrupting the normal functioning of the
hippocampus.
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Common Features of Addiction
 Cannabis
 Long-term damage:
• The effects of long-term marijuana use include
bronchitis, increased risk of lung cancer, poor
ability to control the use of the drug, minor
impairments of attention and memory, and slower
choices in decision making tasks.
• Cognitive impairments from long-term use
appear to be subtle.
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Heredity and Drug Abuse
 Heritability Studies of Humans
• In general, studies have found that the heritability
of smoking is just as strong as that of alcoholism.
• A twin study found that alcoholism and nicotine
dependence have genetic factors in common,
which explains why alcoholics are often addicted
to nicotine.
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