PSY2061 Study Guide - Final Guide: Striatum, Nucleus Accumbens, Drug Action
11 Jun 2018
School
Department
Course
Professor
Nathaniel Parsons
PSY2061 Learning Objectives Week 9 S1 2018
Drugs
Understand the key biological factors involved in the vulnerability for addiction
Addiction is the accumulative effects of repeated drug emission. There are 3 stages of
addiction:
1. Initial drug taking: involving the mesolimbic dopamine system in the nucleus
accumbens (NAc)
2. Habitual drug taking: compulsivity associated with dorsal striatum and prefrontal
systems where cravings develop
3. Addiction: decreased prefrontal control of behaviour, leads to poorer decision making
and increased stress. Anticipation increases and pleasure from effect decreases
(cycle)
There are several factors which can lead to vulnerability for addiction. These includes genes,
where the expression of certain genes in the brain can put people at higher risk of addiction
(nature). Our brain circuits that are moderated by these genes and additionally our
personality traits moderated by these brain circuits are also risk factors for addiction.
Additionally, mental health disorders may put an individual at a higher risk for addiction.
Understand the basic principles of drug action: pharmacokinetics ->
pharmacodynamics
Pharmacokinetics involves the administration, absorption and excretion of drugs into the
body. There are several modes of administration. Absorption refers to the rate at which the
drug enters the bloodstream. Oral absorption is slow and potency is unpredictable
depending on the drug. Lung absorption is the most rapid and of maximum potency.
Injection is also rapid but there can be some loss of potency.
Distribution involves the delivery of the drug to organs in the body. Only a small portion of
the drug actually interacts with the brain. Factors influencing the interaction of the drug with
the brain include blood flow and solubility. The blood brain barrier (BBB) is what seperates
the blood vessels and brain tissue. Passage across BBB depends on lipophilicity,
electrostatic charge, molecular size, “active transport” (the ability of protein receptors on the
membrane to transfer the drug across the BBB. The psychoactive potency of a drug is linked
to how easily it can cross the BBB.
Vaccines are antibodies that bind to the drug so it can’t pass through the BBB. Therefore,
the psychoactive effects of the drug are not felt. It can require self-administration which a lot
of patients don’t follow up on.
Metabolism involves breaking down the drug into smaller molecules or changing fat soluble
drugs into water soluble drugs. Additionally, excretion eliminates the drug and its metabolites
(substance involved in process of metabolism). Drugs usually excreted in urine however they
can also be excreted through sweat, breath and saliva.
Pharmacodynamics involves the drug action – or the drugs effect on the body. Drug action
can work in a variety of ways:
• Mimicking the actions of neurotransmitters and occupying receptor binding sites,
taking the place of the neurotransmitter (nicotine replaces acetylcholine)
• Decreasing the activity of enzymes that destroy neurotransmitters (MAOIs)
• Altering the reuptake of a neurotransmitter (cocaine -> dopamine)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Understand the key biological factors involved in the vulnerability for addiction. Addiction is the accumulative effects of repeated drug emission. Anticipation increases and pleasure from effect decreases (cycle) There are several factors which can lead to vulnerability for addiction. These includes genes, where the expression of certain genes in the brain can put people at higher risk of addiction (nature). Our brain circuits that are moderated by these genes and additionally our personality traits moderated by these brain circuits are also risk factors for addiction. Additionally, mental health disorders may put an individual at a higher risk for addiction. Understand the basic principles of drug action: pharmacokinetics -> pharmacodynamics. Pharmacokinetics involves the administration, absorption and excretion of drugs into the body. Absorption refers to the rate at which the drug enters the bloodstream. Oral absorption is slow and potency is unpredictable depending on the drug. Lung absorption is the most rapid and of maximum potency.
