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Samenvatting Psychopharmacology ()
- Instelling
- Universiteit Utrecht (UU)
Samenvatting van hoofdstuk 1, 5, 6, 7, 8, 9, 10 & 11 van het boek Psychopharmacology (
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Voorbeeld 7 van de 19 pagina's
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Voorbeeld van de inhoud
InhoudChapter 1: What are psychotic drugs? .................................................................................................... 2
Chapter 5: Principles of psychopharmacology ....................................................................................... 3
Chapter 6: Stimulants ............................................................................................................................. 5
Chapter 7: Mood stabilizers ................................................................................................................... 8
Chapter 8: Sedatives and social enhancers ........................................................................................... 11
Chapter 9: Antipsychotics .................................................................................................................... 13
Chapter 10: Psychedelics and related substances ................................................................................. 16
Chapter 11: Dependency ...................................................................................................................... 19
,SUMMARY PSYCHOPHARMACOLOGY (2021/2022) 2
Chapter 1: What are psychotic drugs?
Psychotropic drugs = Substances that influence behavior by acting on the central nervous system (brain).
→ E.g.: Caffeine, Alcohol, Nicotine, Sedatives, Antidepressants, Antipsychotics & Ritalin
Two categories of psychotropic drugs:
1. Recreational Use
o Reward effect
o Calming effect
o Addiction: Repeated self-administration
2. Medicinal Use
o Reduce, change, or otherwise control problem behavior
→ Atropine: Substance that has paralyzing effect; can enter brain from bloodstream, which causes people to
report effects such as slurred speech, drowsiness, or confusion.
→ Melatonin: Travels through bloodstream to transmit signals to part of brain (suprachiasmatic nucleus) that
functions as a biological clock.
Two ways to package a drug in a tablet:
1. Results in the fastest possible rise in blood levels to maximum value. Re-administer medication to
restore peak blood levels. Results in a rather erratic pattern of peaks & troughs in blood level
concentration.
2. Drug enters bloodstream more slowly, making it possible to achieve more constant blood level for
about eight hours after peak achieved by drug administration via first pack method. Ensures a more
constant blood level throughout the day & a more gradual course of effects on behaviour.
Efficacious: Technical term to indicate relationship between dose & occurrence of certain effects through dose-
response curve.
Potency = Denotes the amount of drug needed to produce a given effect.
Efficacy = The maximal effect that a drug produces irrespective of concentration (dose).
Affinity = The extent/fraction to which a drug binds to receptors at any given drug concentration or the firmness
with which the drug binds to the receptor.
Titration: Determining optimal dose.
→ Desired effect achieved for psychoactive drugs after chronic administration/intake.
➢ Up- & down-regulation usually refers to the regulation of the activity of certain receptors located on
cells by hormones.
- Downregulation = A reduction in the activity, sensitivity or number of these receptors.
- Upregulation = An increase in these receptors.
Agonists = Medication that mimics the action of the signal ligand by binding to & activating a receptor;
substances that mimic the action, stimulate its release or inhibit the breakdown.
Partial agonists = Drugs that bind to & activate a given receptor, but have only partial efficacy at the receptor
relative to a full agonist.
Antagonists = Medication that typically binds to a receptor without activating them, but instead, decreases the
receptor’s ability to be activated by another agonist; substances that inhibit or counteract the action.
Therapeutic effect = The response(s) after a treatment of any kind, the results which are judged to be
useful/favorable.
Dopamine antagonists: Block central dopamine receptors in the chemoreceptor trigger zone (CTZ) outside the
blood-brain barrier.
,SUMMARY PSYCHOPHARMACOLOGY (2021/2022) 3
Chapter 5: Principles of psychopharmacology
Grilly & Salamone
Psychopharmacology = Discipline that seeks to study the effects of drugs on behaviour, cognition & emotion.
McKim & Hancock:
Behavioral pharmacology = Study of effects of drugs on behavior.
Psychopharmacology = Studying the effects of drugs on psychiatric symptoms.
Stahl:
Pharmacology = Study of drugs that can affect the brain.
Two principles in psychopharmacology:
1. Dose Response Curve (DRC): Closely related to potency & efficacy concepts; provides insight into how
much of a substance must be administered to achieve a certain effect; results in an indication of optimal
dose (amount) or dosage (amount administered) to achieve desired effect; gives a clear picture of
maximum achievable effect of dust.
- X-axis: Indicates the increasing dose of the substance (mg/kg), where the first unit refers to the
amount of the substance & the second to the weight of the organism or person.
- Y-axis: Indicate effects of dose (e.g. subjective reporting, objective observation of behavior,
brain process or concentration of other substance somewhere in brain or body).
2. Receptor interaction: Belonging to the field of pharmacodynamics.
- Prepulse Inhibition (PPI) = Measure of the ability to regulate an excessive amount of
auditory stimulation.
▪ Hypothesis: Caused by overstimulation of a specific dopamine receptor (D2) in
certain areas of the brain. A substance that stimulates the D2 receptor should
weaken the PPI.
Hypothetical DCR:
Parameters DCR:
a = Potency → Position of the curve along the x-axis
b = Maximum efficacy → The greatest possible response
c = Slope → Change in response per unit dose and half maximum
dose
Therapeutic Window: Shows range between desired & unwanted effects of substance.
➢ Optimal dose differs per individual, so do DRCs for desired and undesired effects.
Psychopharmacology → Interaction between the effect of a substance and the effect of a change of task.
Pharmacodynamics: Describes biochemical & physiological effects of substances; receptor interactions; refers to
the mechanisms & effects of medications within the body (what does medication do to the body & how?).
Biochemical effect = Usually refers to the primary interaction with the receptor, which can bind to an ion
channel or to a transporter, which can somehow change something in the neuron.
Affinity = How well a substance binds to a receptor.
Physiological effect = Refers to the changes in the postsynaptic cell as a result of binding to the receptor of the
substance or to the neurotransmitter.
Receptor Efficacy = Deals with the degree to which the bond between the neurotransmitter and the receptor
results in a synaptic effect.
Pharmacokinetics: Deals with the fate of a substance that has somehow entered the body.
,SUMMARY PSYCHOPHARMACOLOGY (2021/2022) 4
➢ The substance must enter the brain to have a psychopharmacological effect. Unless injected directly
into brain, it must travel to brain via bloodstream.
➢ The blood-brain barrier is a major obstacle between bloodstream & brain. This is formed by a special
kind of lining on the inside of blood vessels that run through brain tissue. Substances that are
sufficiently soluble in fat can penetrate the blood-brain barrier sufficiently to have a psychoactive
effect.
➢ The ease with which substance can pass through the barrier determines the speed & intensity of the
effect of substance on the brain & therefore on behavior & subjective perception.
Rapid dosage forms → Lead to a rapid peak in blood concentration of substance, but also to even rapid decrease,
as blood is constantly pumped throughout the body.
Slow dosage forms → Cause peak blood levels to occur much more slowly & peak reached is not nearly as high
as injection directly into the bloodstream, since a lot of dust is lost in digestive tract & liver; relatively low
maximum level can however, be held longer, because it takes longer for all substances that can be absorbed into
the blood have actually been absorbed.
➢ Substances also differ in how much they resemble an acid, which is one of the factors that allows them
to acquire an electrical charge in the blood.
Ionization = Process by which substances can acquire an electrical charge in the blood.
→ Ionized molecules CANNOT cross the blood-brain barrier!
Tolerance: To achieve the same ((un)desired) effect, increasing doses of substance are needed.
➢ An influential theory (animal research) states that an important factor in the development of tolerance
is the gradual activation of compensatory processes. The compensation process is thought to be
dependent on 'cues'.
Cue = The way the substance is administered or the environment where it usually takes place.
Desensitization: Causes receptors to become less sensitive after repeated stimulation; usually occurs when the
receptor is stimulated more than usual; receptors become less sensitive by reducing the number of receptors
and/or the receptors that lose their affinity for the substance after repeated administration.
Sensitization: Receptors become hypersensitive after repeated administration of a substance with an agonist
effect.
Acute effect = The effect of the first administration of a drug.
Conclusie:
In voorgaande hoofdstukken zijn de algemene principes van hersenfunctie & psychofarmacologie besproken.
Volgende hoofdstukken zullen voornamelijk verwijzen naar de farmacodynamiek van biochemische &
fysiologische effecten, maar ook naar de rol van farmacokinetiek & de doseringen die nodig zijn om effecten te
bereiken op verschillende niveaus, van elementaire hersenfunctie tot gedrag in het algemeen. Het zal duidelijk
worden dat in sommige gevallen dezelfde farmacodynamiek kan optreden in anatomisch gescheiden
hersengebieden, maar in andere niet. Dit houdt rechtstreeks verband met de balans tussen de beoogde effecten
van de psychoactieve stoffen & hun minder gewenste bijwerkingen.
,SUMMARY PSYCHOPHARMACOLOGY (2021/2022) 5
Chapter 6: Stimulants
Stimulants = Class of substances that have a stimulating effect on the body & especially in the brain.
→ 'Sympathomimetic' effect: They stimulate the activity of the sympathetic nervous system.
Stimulants…
- Prepare the body for above-average activity levels by monitoring heart rate & blood pressure increase, widen
bronchi in lungs to facilitate oxygen uptake & activity of stimulate sweat glands.
- Increase the speed with which people can respond to stimuli.
- Improve ability to detect relevant information & make people more alert.
- Have effect on human brain activity.
➢ Electroencephalogram (EEG) can be used to assess general brain activation level & stimulants have the
observed effect of increasing brain activation level.
Main neurotransmitter systems & stimulants with which they respond:
• Adenosine system → Responds to caffeine.
• Acetylcholine system → Responds to nicotine.
o ACh: Neurotransmitter mainly involved in the impulse transmission from nerve cells to
skeletal muscle cells; it transmits stimuli to other places in the body.
o The action potential releases ACh in the terminal of a nerve cell. This ACh diffuses through
the synaptic cleft & activates the latter by binding to the ACh receptor. After activation of this,
if this concerns a second nerve cell, an electrical signal is generated again; if it is a muscle cell,
the receptor activation induces muscle contraction. After a short time, the ACh in the synaptic
space is rapidly broken down by the enzyme acetylcholinesterase into the metabolites choline
& acetate, which are reused to ACh in the original nerve cell.
• Noradrenaline system → Responds to amphetamine, cocaine & methylphenidate.
o Methylxanthines such as caffeine, theobromine, etc. can enhance the receptors for
noradrenaline & provide a more potent effect. Drugs such as cocaine, MDMA & amphetamine
stimulate (each in a different way) the action of noradrenaline.
• Dopamine system → Responds to amphetamine, cocaine & methylphenidate.
o Drugs like cocaine & methylphenidate inhibit presynaptic reuptake of dopamine, leaving more
dopamine in the synaptic cleft & overstimulation of the dopamine pathways (especially the
mesolimbic circuit). These drugs also stimulate so-called opiate receptors. Their cells have the
property that they cancel the inhibitory effect of certain neurotransmitters (such as GABA).
Caffeine:
- Increases responsiveness & mood, which occurs at extremely low doses, while higher doses do not result in
more pronounced effects.
- Potent, but not very effective, substance, with obvious effects on general brain activity, a small sympathetic
activating effect & some effects on the human ability to perform specific tasks, depending on the individual.
- Has a beneficial effect in people who are believed to have relatively little activated brains (extroverted),
compared to people with a presumed high level of activation (introverted).
- Reduces the contribution of relatively slow brain waves (theta and alpha).
- Blocks the adenosine receptor in the nervous system (adenosine antagonist).
Adenosine:
- Substance produced by the brain.
- Inhibiting effect when bound to the adenosine receptor → Reduces secretion of neurotransmitters (e.g.
dopamine, acetylcholine, noradrenaline, glutamate or GABA).
Left: Adenosine (A) is bound to the adenosine receptor,
relatively little secretion of the neurotransmitter.
Right: Caffeine (C) blocks the adenosine receptor, increasing
secretion of the neurotransmitter.
,SUMMARY PSYCHOPHARMACOLOGY (2021/2022) 6
Xanthines/methylxanthines → Caffeine, theophylline (tea) & theobromine (chocolate)
fMRI = Variant of MRI method that identifies where in brain neurons have been active & where they are located.
Gaba:
- Inhibiting neurotransmitter
Left: The reuptake transmitter does its job & there is relatively
little neurotransmitter in the synapse.
Right: Amphetamine (A) blocks the reuptake transmitter &
more neurotransmitter is available in the synapse.
Amphetamine:
- Slowly broken down by liver; effects noticeable within 30 min.; lasts for a long time.
- Stimulate the release of dopamine & norepinephrine in the central nervous system → stimulates CNS
- Mixture of two mirror-image molecules: Dextroamphetamine or Dexedrine.
- Mild variant: Methylphenidate = Ritalin → ADHD
- Interact with the reuptake transmitters in two ways:
- Binds to transporter & therefore block it, which reduces reuptake, so more neurotransmitter (e.g.
dopamine, noradrenaline & serotonin) is available in the synapse to do post-synaptic things.
- Promote the reverse-transport process.
- Sympathomimetic effect ascribed to the interaction with noradrenergic transmission.
- Long-term use:
- Long-term increased release of dopamine → Desensitization of dopamine receptors.
- Long-term use → Damage to dopamine neurons → Less release of dopamine → Receptors become
over-sensitive.
Methamphetamine:
- A potent full agonist.
- Completely inhibits or reverses the transport direction of dopamine, noradrenaline & serotonin transporters.
- Inhibit reuptake (e.g. dopamine & noradrenaline) & promote reverse transport.
- Long-term effect: Amphetamine psychosis (e.g. symptoms of schizophrenia) → Possibly caused by
excessive activity of the dopamine system.
Dextroamphetamine:
- Inhibit reuptake & promote reverse transport.
- Stimulates central nervous system & increases the release of mainly noradrenaline & dopamine as an agonist &
reuptake inhibitor; also affinity for serotonin, but in most cases this is negligible.
Methylphenidate:
- Influences reuptake.
- Little effect on reverse transport away from the brain.
- Reduces dominance of theta waves.
- Related to an increase in the amount of dopamine available.
- Inhibits the noradrenaline reuptake transporter & the dopamine transporter.
Atomoxetine:
- Selectively inhibits the noradrenaline reuptake transporter & NOT the dopamine transporter.
- Dopamine reuptake is performed by the noradrenaline transporter.
, SUMMARY PSYCHOPHARMACOLOGY (2021/2022) 7
Cocaine:
- Blocking noradrenaline transporters & especially dopamine transporters.
- Blocks the reuptake of serotonin, noradrenaline & dopamine into neuron from the synaptic cleft in the brain →
Creates a greater concentration of these three neurotransmitters.
- Little effect on reverse transport away from the brain.
- Has beneficial effect on cognitive function in experienced users.
- Long-term effects: Disastrous for cognitive functioning (e.g. arteriosclerosis).
➢ Cocaine strongly resembles methamphetamine, but methamphetamine last much longer.
Alcohol + Cocaine = Cocaethylene → Delays the breakdown of cocaine & has un itself similar effects.
➢ The method of administration (oral vs. injection, smoking or snorting) has the greatest effect on the
sympathetic & subjective effects of both cocaine & methylphenidate.
Nicotine:
- Pronounced subjective effects: No sense of euphoria, no altered sensory perception & unclear mix of calming
& stimulating effects.
- Stimulates nicotine-acetylcholine receptor (nAChR = Activating link in the sympathetic nervous system) &
therefore indirectly stimulates dopamine → Gives nicotine sympathomimetic effects → nAChR is
hypersensitive in smokers.
- Opens sodium ion channels in the brain → Partially results in action potentials & the release of
neurotransmitters in the synaptic connections with other neurons.
- Leads to desensitization of nicotine receptor in skeletal muscles.
- Might have a positive influence on human learning ability.
- Nicotine affects the ACh receptors, but breaks down poorly compared to ACh → Receptors are overstimulated
& with repeated use, the receptors become temporarily less sensitive & more receptors are produced. Tolerance
and withdrawal symptoms occur.
- Indirect effect on the availability of dopamine in the nucleus accumbens (reward system).
Modafinil:
- Blocks dopamine & noradrenaline transporters (just like amphetamine & methylphenidate).
- Influences the orexin-histamine system → Effect of activating the cortex.
- Increases serotonin levels in rats.
- Increases heart rate & blood pressure.
- Enhances feelings of excitedness & alertness.
Acetylcholine-esterase inhibitors:
- Inhibit the breakdown of acetylcholine by inhibiting the esterase → Increase in the amount of acetylcholine
available & therefore increased stimulation of the ACh receptors.
AMPAkines:
- Agonistic effect on the AMPA-glutamate receptor.
Conclusie:
Stimulantia zijn zeer verschillend in hun werkingsmechanisme & hun effecten overlappen elkaar slechts
gedeeltelijk. Sympathische effecten van de verschillende stimulerende middelen zijn redelijk consistent, maar
hun gedragseffecten kunnen sterk variëren, evenals hun potentieel voor verslaving. Voor sommige stoffen, zoals
methylfenidaat, zwaait de balans tussen positieve effecten op gedrag e& ongewenste bijwerkingen zo ver naar de
gunstige kant dat ze geschikt zijn voor een breed scala aan klinische toepassingen. Ook voor gezonde personen
kunnen deze & andere stoffen interessante toepassingen bieden.
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