Chapter 6 (MT2) Flashcards
Drugs and Hormones
Psychopharmacology
The study of how drugs affect the nervous system and behaviour
What influences how drugs effect people?
Secondary or unintended actions of the drugs
Individual differences (genetic makeup, adverse childhood experiences, sex, age, height)
Drugs
Chemical compounds administered to produce a desired change
Psychoactive drugs
Substance that acts to alter mood, thought, or behaviour, used to manage a neuropsychological illness
Route of administration (definition and examples)
The way a drug enters and passes through the body to reach its target
- injecting directly to brain
- injected into muscles
- injected into bloodstream
- absorbed through skin
- inhaled into lungs
- rectally (suppository)
- orally
- weak acids pass from stomach to bloodstream
- weak bases pass from intestines to bloodstream
Where are drugs broken down (catabolized)
Kidneys, liver, intestines
How are drugs excreted
Urine, feces, sweat, breast milk, exhaled air
Some cannot be removed and can build up/become toxic (eg. Hg)
What prevents most substances (including drugs) from entering the brain via the bloodstream?
The blood brain barrier, using tight junctions
Why do substances move into and out of the bloodstream more easily?
Endothelial cells in capillaries are not tightly joined
Which three brain regions lack a blood brain barrier?
Area postrema (allows toxic substances to enter to induce vomiting)
Pituitary gland (entry of chemicals that influence pituitary hormones)
Pineal gland (entry of chemicals that effect day/night cycles)
What else enters the brain despite the blood brain barrier?
Fuel (oxygen and glucose)
Amino acids to build proteins
Some drugs
What are the two ways that molecules of vital substances cross the blood brain barrier?
Small molecules pass through the endothelial membranes
Complex molecules carried across membrane by active transport systems or ion pumps
Agonists
Antagonists
Agonists increase neurotransmission, antagonists decrease it
How do drugs modify synaptic actions (how they work)
(1) Synthesis of neurotransmitter in cell body, axon, or terminal
(2) Packaging and storage of neurotransmitter in vesicles
(3) Release of transmitter from presynaptic terminal
(4) Receptor interaction in postsynaptic membrane
(5) Inactivation by reuptake into presynaptic terminal for reuse, or by enzymatic degradation of excess neurotransmitter
Tolerance
Decreased response to a drug with repeated exposure
A learned behavior results when a response to a stimulus
weakens with repeated presentations
Metabolic tolerance
Increase in number of enzymes in the liver, blood, or brain needed to break down a substance
Cellular tolerance
Activities of brain cells adjust to minimize effects of the substance
Learned tolerance
People learn to cope with being intoxicated
Sensitization
The increased responsiveness to successive doses of a substance
What may underly the development of beneficial effects of drugs?
Sensitization - drugs may need to be taken for several weeks
What must happen before someone becomes dependent on a drug?
One must be sensitized by numerous experiences with the drug away from the home environment
What can produce effects resembling sensitization that prime the nervous system for addiction?
Life experiences, especially stressful ones
Categorization of psychoactive drugs (based on their primary neurotransmitter system of action)
- Adenosinergic antagonist
- Cholinergic agonist
- GABAergic agonists
- Glutamatergic antagonists
- Dopaminergic agonists
- Dopaminergic antagonists
- Serotonergic agonists
- Opiodergic agonists
- Cannabinergic agonsists
Zoopharmacognosy
Behaviour where nonhuman animals self-medicate
Adenosinergic
Caffeine (mild dependence)
- Binds to adenosine receptors without activating them (adenosine induces drowsiness)
- Inhibits an enzyme that breaks down cAMP (increase in cAMP results in more energy)
- promotes release of other neurotransmitters (like dopamine), leading to stimulant effects
Cholinergic
Cholinergic = mimic ACh
Nicotine (dependence involves psychological and physical aspects)
(tobacco, tomato, potato, eggplant)
(stimulant in low doses, dampens neuronal activity at high doses)
- nicotine stimulates ACh nicotinic receptors, indirectly causes the release of other neurotransmitters (dopamine gives reinforcement)
GABAergic
(lower dose)
normal
anxiety relief
disinhibition
sedation (median dose)
sleep
general anesthesia
coma
death
(higher dose)
Alcohol, benzodiazepines (valium, xanax)
Glutamergic
Receptors of glutamergic system: NMDA, AMPA, kainite
Antagonists for the NMDA receptor can produce hallucinations and out-of-body experiences (PCP, ketamine)
Both PCP and ketamine produce feelings of detachment/dissociation from the environment/self because they distort perceptions of sight/sound (dissociative anesthetics)
Dopamine agonists
Methamphetamine (synthetic)
Amphetamine (adderall) and methylphenidate (ritalin) are prescribed for ADHD
Cocaine, amphetamine, meth all used recreationally
The use of dopamine antagonist drugs that preferentially
bind to D2 receptors has improved the functioning of people with schizophrenia
Tardive dyskinesia
Movement disorder resulting from long term use of D2 antagonists characterized by involuntary, repetitive movements such as grimacing, lip smacking, rapid jerking or slow writhing movements
Serotonergic
Used recreationally (good and bad trips)
Naturally occurring (plants and mushrooms): mescaline, DMT, psilocybin
Synthetic: LSD, MDMA (ecstacy)
Major depression (and what is prescribed?)
Mood disorder characterized by prolonged feelings of worthlessness and guilt, disruption of normal eating habits, insomnia, a general slowing of behaviour, and frequent thoughts of suicide
Serotonergic agonists prescribed
Opioid
Any endogenous or exogenous compound that binds to
opioid receptors to produce morphine-like effects
Sleep-inducing (narcotic) and pain-relieving (analgesic) properties
Three sources of opioids
– Isolated (morphine, codeine)
– Altered (heroin, oxycodone)
– Synthetic (fentanyl and methadone)
Five classes of opioid peptides
Dynorphins, enkephalins,
endorphins, endomorphins, and nociceptin
Active ingredient of opium
Morphine
(codeine and morphine isolated from opium in 1805)
Physiological changes of opioid ingestion
– Altered pain perception
– Euphoria
– Constipation
– Respiratory depression
– Decreased BP
Semi-synthetic and synthetic opioids
SS: Heroin and oxycodone
S: Fentanyl
What is a competitive inhibitor of opioids?
Naloxone (narcan)
Cannabinergic
Tetrahydrocannabinol (THC) is one of 84 cannabinoids and the main psychoactive constituent in cannabis
- THC alters mood by binding to cannabidiol (CB1) receptor and with CB2 receptors on glial cells/other body tissue
What disorders is THC and CBD useful for?
– Relieves nausea & vomiting (chemo)
– Stimulates appetite (anorexia)
– Chronic pain
- MS
– Epilepsy
– Glaucoma
Substance use disorder
A pattern of drug use in which people rely on a drug chronically and excessively, allowing it to occupy a central place in their life
Withdrawal symptom
Physical and psychological behaviour displayed by an addict when drug use ends
Addiction
A complex brain disorder characterized by escalation, compulsive drug taking, and relapse; called substance use disorder per the DSM-5
Psychomotor activation
Increased behavioural and cognitive activity so that at certain levels of consumption, the drug user feels energetic and in control
Adverse childhood experiences (ACEs)
Environmental factors associated with an increased risk of drug initiation and drug addiction including:
– emotional, physical, and sexual abuse or neglect, mental illness/substance abuse/incarceration of/by a household member, parental separation/divorce, & witnessing violence against one’s mother
Are men or women more sensitive to drugs?
Are men or women more likely to abuse drugs?
Women, women
The neural basis of addiction: wanting-and-liking theory
When a drug is associated with certain cues, the cues themselves elicit desire for the drug
wanting = craving
liking = pleasure
With repeated use:
– Tolerance for liking develops, and the expression of liking decreases
– Wanting sensitizes, craving increases
Where is the decision to take a drug made?
Prefrontal cortex
- drug activates opioid systems related to pleasurable experience
- wanting drugs springs from dopaminergic activity
Why aren’t we all addicted to drugs?
Genetics - no specific gene, but any explanation of drug use requires genetic and learning components
Epigenetics - can account both for the enduring behaviours that support addiction and for the tendency of drug addiction to be inherited
How does chronic alcohol use cause brain damage?
Alcohol does not directly cause damage to thalamus/limbic system:
Alcoholics typically obtain low amounts of thiamine (vitamin
B1) in their diet, and alcohol interferes with intestinal absorption of thiamine
Where does the strongest evidence that drugs cause brain damage come from?
Strongest evidence comes from the study of the synthetic
amphetaminelike drug MDMA (Ecstasy)
– In animal studies, doses of MDMA (approximating those
taken by human users) result in the degeneration of very fine serotonergic nerve terminals
Feedback system of hierarchical control of hormones
- Hypothalamus produces
neurohormones - Neurohormones stimulate
pituitary gland to secrete
hormones into bloodstream - Hormones influence endocrine
glands - Endocrine glands release
hormones & send feedback to
the brain
Functions of hormones
Treat/prevent disease, replacement therapy, counteract aging, increase strength & endurance
Classes of hormones
Peptide or steroid
Steroid hormone
Fat-soluble chemical messenger synthesized from cholesterol. E.g., gonadal (sex) hormones, thyroid
Peptide hormone
Chemical messenger synthesized by cellular DNA that acts to affect the target cell’s physiology. E.g., insulin, growth hormone
Functional groups of hormones
(1) Homeostatic hormones: Maintain internal metabolic balance and regulation of physiological systems
(2) Gonadal (sex) hormones: Control reproductive functions, sexual development, and behaviour
(3) Glucocorticoids: Secreted in times of stress; important in protein and carbohydrate metabolism
Anabolic-androgenic steroids
A class of synthetic hormones related to the male sex hormone testosterone that have both muscle-building (anabolic) and masculinizing (androgenic) effects
Stressor
A stimulus that challenges the body’s
homeostasis and triggers arousal
Stress response
Physiological and behavioural arousal and attempts to reduce stress
Activating a stress response
Fast acting: primes body immediately for fight or flight (epinephrine)
Slow acting: mobilizes the body’s resources to confront a stressor and repairs stress related damage (cortisol)
