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Chapter 9

PSY290H1 Chapter Notes - Chapter 9: Olfactory Tubercle, Headache, Amygdala

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Joe Kim

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Chapter Fifteen: Drugs and Addiction
15.1 Basic Principles of Drug Addiction
There are more than a billion people addicted to substances around the world
Pharmacological: scientific study of drugs
Drug Administration and Absorption
Psychoactive drugs: drugs that influence subjective experience and behaviour by
acting on the nervous system
drugs can be administered in four ways : oral, injection, inhalation, and absorption
(mouth, nose or rectum)
how they are taken determines the rate and degree at which it arrives at a site in the
body and its effect
Oral Ingestion
many drugs are taken this way
when swallowed they dissolve in the fluid of the stomach and carried to
in the intestine they are then absorbed into the bloodstream
drugs that can pass through the stomach wall have a faster effect (ex. Alcohol)
drugs that don’t get absorbed in the intestinal wall or are broken down to
metabolites must be taken through some other route
2 main advantages: easy to take and relatively safe
disadvantage: unpredictability – absorption to the bloodstream may depend on
the amount of food that is present in stomach
owhy some drugs are told to take on empty stomach or after a meal
effects of injections are strong, fast, and predictable
drug injections are made:
osubcutaneously (SC): into fatty tissue beneath skin
ointramuscularly (IM): intro large muscles
ointravenously (IV): directly into veins right underneath skin
Addicts prefer IV route because the bloodstream will deliver drug straight to
the brain
Disadvantage: once in the bloodstream difficult to counteract effects of
overdose, impurity and allergic reaction
oAlso they develop scar tissue, infections, and collapsed veins
Absorbed to the bloodstream via the capillaries in the lungs
Ex. Anesthetics are delivered through inhalation, also tobacco and marijuana
Disadvantage: difficult to regulate dose, if used chronically will damage lungs
Absorption through Mucous Membranes
Cocaine is taken through the nasal membrane
Absorbed through the mucous membrane of mouth , nose, or rectum
Causes damage to the membrane

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Drug Penetration of the Central Nervous System
once in bloodstream drugs are carried to the blood vessels of the CNS
blood-brain barrier prevents some harmful drugs from passing into the neurons of the
Mechanisms of Drug Action
some drugs (alcohol and other anesthetics) act on neural membranes throughout the
others bind to specific synaptic receptors
oaffecting the synthesis, transport, release and deactivation of specific
neurotransmitters, or effecting the chain of chemical reactions in post synaptic
neurons by activating receptors
Drug Metabolism and Elimination
drug metabolism: process of enzymes in the liver converting an active drug into its
non-active form
usually by preventing it from passing through the lipid membrane of cells, so it does
not pass through the blood-brain barrier
some drugs can pass as urine, feces, breath and mother’s milk
Drug Tolerance
drug tolerance: decreased sensitivity to a drug as a result of exposure to it
seen by: dose of drug has less of a effect or that it takes more of that drug to produce
the same effect (a shift in dose-response curve pg. 370)
3 main points to drug tolerance
1. Cross tolerance: one drug can produce tolerance for other drugs that act by
the same mechanism
2. Drug tolerance develops to some effects of a drug but not to others
ex. The nauseating effect of alcohol is gone, but you can still get really
drunk (only one effect subsided)
drug sensitization: increasing sensitivity to a drug
3. Not a single mechanism to drug tolerance, many different adaptive changes
occur to reduce effects
2 categories of changes underlie drug tolerance:
Metabolic tolerance: reduced amount of the drug getting to its site of action
Functional tolerance: changes that reduce the reactivity of the sites of action
Tolerance to psychoactive drugs is mainly functional
Exposure to drugs can reduce the number of receptors for it, decrease efficiency of
binding, diminish impact of receptor binding to activity of the cell
Drug Withdrawal Effects and Physical Dependence
Withdrawal syndrome: the sudden elimination of a drug that has been in the body
for a long period of time
Usually opposite effects to the initial ones of the drug
Ex. Sleeping pills often produce insomnia when not continuously taken

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Physically dependent: when an individual who experiences withdrawal reactions
when they stop taking a drug
Because withdrawal effect are opposite to initial effects it is thought that it may be
produced by the same neural changes that produce drug tolerance (figure 15.2 pg.
Drug Addiction: What is it?
Drug addict: are habitual drug users who continue to use a drug even though they
know the effects on health, social life, and repeated efforts to stop
Addicts do not just take drugs to stop withdrawal symptoms, or else it would be easily
15.2 Role of Learning in Drug Tolerance
Contingent Drug Tolerance
Contingent drug tolerance: demonstrations that tolerance develops only to drug
effects that are actually experienced
Focuses on what the subject is doing while under the influence of drugs
Before-and-after design : two groups receive the same amount of drugs, one
receives it before each test and the other receives it after a test. At the end both groups
receive drug followed by the test in order to measure its effects
Pinel did experiment with rats (used alcohol and mild convulsive amygdala
Found that rats given alcohol after the convulsive stimulation did not become
Those who were given alcohol before the convulsive stimulation became
Conditioned Drug Tolerance
Focus on the situation in which drugs are taken
Conditioned drug tolerance: demonstrations that tolerance effects are maximally
expressed only when a drug is administered In the same situation previously
2 groups of rats tested , given 20 injections of alcohol and 20 of saline, one group got
alcohol injection in test room and saline in colony room, other opposite
they measured the hypothermic response, tolerance was only observed in the
environment in which the rats received the alcohol injections (situational specificity
of drug tolerance)
hypothesis (Siegel and colleagues) : addicts are more likely to overdose in new
contexts, because in the usual locations they are tolerant and may increase the amount
the take, when taking the same amount in a new place (not tolerant) they are likely to
overdose (seen in rats who were administered large amounts of heroine in a novel
environment , died)
conditioned compensatory responses: conditioned stimuli that predict drug
administration come to elicit conditional responses opposite to the unconditional
effects of drugs
(conditional stimuli) exteroceptive stimuli : external, public stimuli ex. Drug
administered environment
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