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PSYB65H3 Study Guide - Final Guide: Neurotransmitter Receptor, Anxiolytic, Temporal Lobe

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Ted Petit
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PSYB65: Human Brain and Behaviour
Lecture 7 Mechanisms of drug action, psychopharmacology of neural stimulants (Chapter 9, 15)
Monday, November 5, 2012
Global Overview of How Drugs are Classified
1. Prescription drugs
o Doctors prescribe them for you
o What drugs are considered legal or illegal varies over time and across different countries
2. Over-the-counter drugs
o Don’t need a prescription from a doctor
o Example: in Canada, Codene can be bought through over-the-counter
o In the US, it’s considered illegal to buy Codene from the pharmacy (must be prescribed by a doctor)
3. Social drugs
o Social types that can be bought on a regular basis
o Examples: Nicotine, alcohol, caffeine (coffee, tea, Coke, Pepsi, etc.)
4. Drugs that are not produced commercially or, if they are produced commercially, they are not produced
for their psychoactive effects
o No one manufactures it, so you can’t just go out to the store to buy it
o Example: Marijuana
o Example: Airplane glue produced commercially but not produced for its psychoactive effects
Tolerance and Withdrawal Overview
A concept that if a drug is taken repeatedly, most drugs show a decreasing behavioural effect
o Basically, the more you take the drug, the less behavioural effect it has
What causes tolerance to occur?
If you have drugs that alter a transmitter system, the more you stimulate/alter the system, the postsynaptic side
of the system will compensate
o Example: the more you stimulant a system, the more it will compensate by either reducing the number
or sensitivity of the receptors
If you’re using something that slows the system down (like a depressant), you’re getting under-activity of the
system, then the system will compensate by increasing the number or sensitivity of the receptors
The Mechanism of Tolerance
Whenever you take a stimulant(drug) it will cause an excess amount of NT to be released so there is more
transmitter substancehyper stimulation of synaptic receptors PLASTIC RESPONSE: reduce the number of
the postsynaptic receptors and it will compensate for the over active stimulation, so then the postsynaptic
neuron won’t fire regularly because it has its own regulation : so over time when you take the same amount of
drug over time, you don’t get the same, strong enough effect behaviourally (decrease of sensitivity in the
receptors) TOLERANCE: you take the same amount of drug and you don’t feel as high after a long period of
It’s never permanent on the brain, cyanide is permanent
Example of Cause with Stimulant
Whenever a drug (ex. stimulant) is taken normally, it will cause excess amounts of transmitters to be released
due to different mechanisms winds up with more transmitter substances stimulating the postsynaptic neurons

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As more and more neurotransmitters are released and there is hyper-stimulation of the receptors, receptors are
bombarded; there is classic response from postsynaptic receptor that will result in the reduce the number of
sensitive of the postsynaptic receptors
Will start reducing the number of receptors that it has to compensate for overactivation postsynaptic will not
fire as often (self-regulates / tones down sensitivity of receptors)
Example of Cause with Depressant
Depressant is slowing down functional activity decreases activation of postsynaptic cell realizes that it is not
hitting the normal number activity that it should, will start to increase in the number / sensitivity of postsynaptic
Will respond by building more receptors to compensate for the depression of brain same amount of drugs
that will stop 4 receptors will not have to stop 8 receptors
Instead of person being depressed, the drugs will no longer have the same
dramatic event, won’t be relaxed as much
Depends on the drug that whether a tolerance effect may be produced
Withdrawal definition
If you have been taking the drug for over a long period of time (a very long time) and then you suddenly stop
taking it
Once you stop, you obviously begin to have cravings for the drug
o Example: smokers
In general, the behavioural effect of withdrawal is exactly the opposite of the effect of the drug itself
The effects can be quiet severe
The Mechanisms of Withdrawal
The presynaptic isn’t bombarding the postsynaptic side
When a person comes off a drug, they postsynaptic cell is being under stimulated and will go below average
When someone who is taking a stimulant and comes off of it, they become depressed and eventually come
back to normal. When they are withdrawing from the stimulant, they are tired, they are sad, exhaustion
A person who is on a depressant gets super stimulated (ie: shaking, seizures) and high and comes back to
Withdrawal from a depressant can be life threateningyou run the risk of the brain going into a seizures and
becoming too active, you can’t take someone off a depressant cold turkey
If you give a person a stimulant, and then take it away, they will become depressed (tired)
If you give them a depressant (barbiturates, alcohol), and then take it away, they will have a excited period of
time (hyperexcitable brain) agitation, good chance it can cause a seizures and death
o Don’t ever take a person off depressants right away, because the consequences can be severe (can
cause death)
o Give them valium, that helps substitute the depressant without the behavioural effects
Applies to all drugs
Person enjoys and becomes depend on the drug
o Implies that the person wants to have the drug, a behavioural or physical dependence on the drug, a
requirement for the drug
However, there are different levels of addiction:

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(1) Psychological Addiction
The person has become behaviourally dependent on the particular drug
o Very attached to the drug and can’t let go of it
Not a meaningful term, but has a slight meaning
(2) Physical Addiction
On withdrawal, if you take the drug away, there has to be some physical withdrawal symptoms
Symptoms can be something that is measured
o There is a clear physical indication that can be seen
o Examples: sweating, changes in Galvan response, seizures, blood pressure, body temperature
As a general rule: the more rapid the affect (behavioural) of the drug, the more addicting the drug is
EXAMPLE: cocaine grows on the coca tree, and people in Bolivia use the leaves to take the cocoa leaves and make
a tea because it’s a light stimulant
imported into Canada in very concentrated. CRACK cocaine: is much more
concentrated, and gives an instant rush and injected cocaine becomes more addicting
o Same chemical in a form with a powerful rapid effect, it can become very very addicting
Activates the Central Nervous System
All of these stimulants cause an arousal in the cortical EEG
o When they take a stimulant, the EEG will shift into an arousal state and they inhibit sleep
Mild Stimulant Caffeine
Many students ingest this stimulant
Found in coffee and tea
Inhibits sleep
Coffee has more caffeine than tea (they have many levels of caffeine depending on the type, but tea usually has
less caffeine than coffee)
Many headache remedies has caffeine within them
Stimulates the digestive system
Tolerance: some tolerance does develop towards caffeine, but it’s very little
Withdrawal: headache (because caffeine stops headache), constipation (must be drinking 6-8 cups of coffee a
Toxicity: it’s not very toxic, it’s estimated 70-100 cups of coffee at one time can be toxic and it can kill you
Mechanism: it inhibits the breakdown of cyclic AMP (cAMP), it causes an increase in the amount of cAMP, this
leads to an increase in glucose production which causes heighten cellular activity
o Works with cellular activity rather than neurotransmitters
Found in tobacco leaves (formed into cigars and cigarettes)
It mimics ACh , thereby stimulating at the postsynaptic neurons also known as nicotinic receptors
Other effects: also causes release of adrenaline, which causes an increase in heart-rate and blood-pressure
Tolerance: some does develop, but it’s not bad (example: smokers would smoke about ½ pack a day and
maintain that)
Withdrawal: craving leads to depression
Toxicity: not very high, can be a problem for infants who have eaten/chew a cigar; it can cause death
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