Addiction – Session 2: Neurobiology and neurocognitive
aspects
Literature: Theme 2. Neurobiology and neurocognitive aspects
2.1 Biological mechanisms and neurotransmitters
- Moss, A. C., & Dyer, K. R. (2010). Psychology of Addictive Behaviour. New York: Palgrave
MacMillan. Chapter 2 The biology of addictive behaviors
- Leshner, A. I. (1997). Addiction is a brain disease, and it matters. Science, 278(45), 45–47
- Casey, B. J., & Jones, R. M. (2010). Neurobiology of the Adolescent Brain and Behavior:
Implications for Substance Use Disorders . Journal of the American Academy of Child and
Adolescent Psychiatry, 49(12), 1189–1201. doi:10.1016/j.jaac.2010.08.017
2.2 Craving, aandachtsbias and loss of control
- Moss, A. C., & Dyer, K. R. (2010). Psychology of Addictive Behaviour. New York: Palgrave
MacMillan. Chapter 4 Understanding Addictive behaviors as a problem of control
- Franken, I. H. A. (2003). Drug craving and addiction: integrating psychological and
neuropsychopharmacological approaches. Progress in Neuro-Psychopharmacology and
Biological Psychiatry, 27(4), 563–579. doi:10.1016/S0278-5846(03)00081-2
- Field, M., & Cox, W. M. (2008). Attentional bias in addictive behaviors: A review of its
development, causes, and consequences. Drug and Alcohol Dependence, 97(01-Feb), 1–20.
doi:10.1016/j.drugalcdep.2008.03.030
2.3 Consequences of substance abuse
- Forray, Ariadna,. (2016). Substance use during pregnancy. F1000Research, 5, 887–887.
doi:10.12688/f1000research.7645.1
- Galanter, M., Kleber, H. D., & Brady, K. T. (Eds.). (2015). Textbook of substance abuse
treatment. Arlington: American Psychiatric Publishing. Chapter 40 Perinatal Substance use
disorders
- Squeglia, L. M., & Gray, K. M. (2016). Alcohol and Drug Use and the Developing Brain.
Current Psychiatry Report, 18(46), 1–10. doi:10.1007/s11920-016-0689-y
2.4 Markers
- Frederick, J. A., & Iacono, W. G. (2006). Beyond the DSM: Defining endophenotypes for
genetic studies of substance abuse. Current Psychiatry Reports, 8(2), 144–150.
doi:10.1007/s11920-006-0014-2
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,Moss, A. C., & Dyer, K. R. (2010). Psychology of Addictive Behaviour. New York: Palgrave
MacMillan. Chapter 2 The biology of addictive behaviours.
The Biology of addictive behaviour:
Introduction:
- The brain strives for a balance and when the balance is upset, the brain will seek to adapt to
redress this imbalance, by minimizing the effects of the drugs
- Drug: chemical substance, with a known chemical structure that produces a biological and
psychological effect when it is administered. Drugs can be obtained from plants, animals,
genetic engineering, or may be synthetic. Administered to the body. All drug abuse produce a
sought after or pleasurable effect. They are rewarding to use in some way.
- Phases of drug use:
o Routes of administration: smoke, inject, or drink it. Change how long it takes for us to
feel the effect, how intense the effect is, and how long it lasts
o Absorption and distribution: how does the drug reach the brain
o Metabolism and excretion the effects of the drug will wane, the body will break
down the drug molecules and remove it.
- Drugs work mainly on receptors (and enzymes, neurotransmitter carriers and ion channels),
receptors are protein molecules that recognize and respond to endogenous chemical
compounds called neurotransmitter(which sends messages between the cells in the brain).
Individual classes of drugs only bind to certain receptors
- Tolerance and physical dependence show that the body will adapt, leading to a reduction in
the effect of the drug. Therefore this may lead us to increase the among and frequency
Routes of administration:
- Common routes of administration for drugs of abuse:
o Oral (drinking with a liquid or taking a pill). Slowest way of administrating
o Injection: injecting into a vein (intravenous), into a muscle (intramuscular), or slightly
under the skin (subcutaneous). Very effective, feel the effects very quickly. But also
dangerous (skin lesions, vein damage, injecting crushed pills may cause damage, HIV
or AIDS).
o Inhalation: heated vapours or smoking
o Application to skin: applying an ointment
o Mucous membranes: by sniffing a drug (intranasal) or holding liquid in your mouth.
Slow way of administrating drugs
- Route of administration will depend on chemical characteristics of the drug and personal
preference. Chemical structures can
be changed. Choice can also be
guided by how fast people want their
drug to act. The slower the onset of
drug action, the more gradual the
build up of the effect and the longer it
will seem to last.
Absorption:
- Absorption: the process by which a
drug enters the blood stream after it
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, has been administered. The difference in time for a drug to produce an effect can be
explained by rates of absorption, numbers and nature of barriers to cross to get into the
bloodstream.
- Factors that determine speed and success with which a drug will cross these cellular barriers:
o The degree to which the drug is soluble in lipids (fats): so how easy the drug can
move through a cellular membrane (made of lipids) is determined by the degree to
which the drug will be dissolved in the membrane lipids.
o The degree of ionization of the drug: the ionized version of a drug is much less likely
to cross the cellular membrane than the deionized form proportion ionized
molecules in drugs.
o The size of the drug molecule: smaller molecules will pass faster through the
membrane, also the vehicle in which the drug is administered can be important as
some are designed to release the drugs slowly over time.
o The difference in concentration of the drug on the two sides of the membrane: the
greater the difference the more rapid the movement (diffusion)
- Routes of administration:
o Intravenous Injection: quickest rate of absorption
o Inhalation: second quickest, as lungs are specialized in absorption (high lipid
solubility and small molecules)
o Mucous membrane: heavier barrier by several layers of cells
o Intramuscular or subcutaneous injection: rate of absorption is very depend on how
close the injection site is to a blood vessel
o Oral route: slowest rate of absorption as most of the absorption will happen in the
small intestine, little in mouth and stomach (acid environment, much ionization). If
the stomach is empty, the drug will travel to the small intestine much faster. The
small intestine ranges from weakly acidic at one end to weakly alkaline at the other,
increasing absorbance.
- Absorption rates are influences by the route of administration, chemical properties of the
drug, conditions at the site of administration, individual health factors.
Distribution:
- The process of drug movement through body into the brain.
- The easier the drug is absorbed, the more widely and evenly the drug is distributed. The drug
becomes diluted before reaching the brain.
- Important barriers to cross are the lining of the gastrointestinal tract and the blood brain
barrier:
o Blood-brain barrier: cellular lining of the capillaries of the brain which makes it
difficult for drugs to enter the brain and is a defence against chemicals and other
foreign bodies. Large, ionized or non-lipid soluble molecules will have difficulty
crossing this barrier.
Drug elimination: metabolism and excretion:
- Metabolism and excretion are how the body eliminates a drug and terminates its effect
o Metabolism: the way in which the body breaks down the drugs, making it easier to
remove, and involves a chemical reaction within the body to form a product which is
easily excreted. The chemicals produced to metabolize the drugs are Metabolites
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, which in case of activity may produce an effect in the brain similar to the original
drugs.
o Excretion: the elimination from the body o the drug and its metabolites
- Drug excretion:
o Gasses through the lungs by breathing, but also alcohol and other solvents
o Non-gasses: body fluids including saliva, sweat, tears, mucous secreted from nose,
urine, human breast milk.
Mostly urine importance of kidneys as they filter the blood. Ionized or
non-lipid soluble cannot re-enter circulation. Therefore, metabolized drugs
are formed into ionized products.
- Drug metabolism:
o Takes mostly place in the liver as the liver has a high concentration of enzymes which
can inactivate the drugs to a form more easily excreted by the kidneys
Time-effect and dose-effect relationships:
- The length of time it takes for a drug to stop producing the effect and leave the body is
governed by many factors including characteristics of the drug and the form in which it is
taken, the route of administration and the health and functioning of the body.
- The role of metabolism and excretion on drug concentrations over time: the rate to which a
concentration of a drug will rise and fall.
o Rate higher when there is a higher concentration of drugs in the system compared.
There are exceptions to this and some drugs will be metabolized at a constant rate;
when drugs require a particular enzyme to be metabolized and the availability of
these enzymes is limited.
o The processes of absorption, distribution and elimination do not occur
independently, they operate in the same time resulting in a constant fluctuation in
concentration of drug at the site of action
- The role of individual variability on drug concentrations over time:
o Individual differences such as body weight, gender, age, health status and those due
to genetic make-up will affect the time course of a drug’s presence and the intensity
of its effect.
Women have a different body compositions compared to men
Both very young and the very old have a reduce ability to metabolize and
excrete drugs than other people
An individual’s genetic make-up is expressed in protein structures and may
alter drug action in multiple ways e.g. the amount of the enzyme
responsible for metabolism of certain drugs may be missing. It shows how
we respond to a drug, either positively or negatively
Drugs and the central nervous system:
- The principles of neurotransmission:
o Neurons: specialized cells that both receives information from other neurons and
pass the information on to other neurons, so to continue the information flow
throughout the brain
o Reward pathway: a pathway of neurons that passes through the limbic region. If
activated, we will feel happy. All drugs abuse activation of the reward pathway
o Action potential: information send through a neuron
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