5- Psychoactive Drugs Flashcards
5 types of drugs that act on the dopamine system
L-DOPA
Antipsychotic drugs
Recreational drugs
Cocaine
Amphetamine
What does L-DOPA treat?
Parkinson’s disease
What is Parkinson’s caused by?
A loss of dopamine neurons
What do Parkinson’s patients have difficulty doing?
Initiating movements
How does L-DOPA treat Parkinson’s?
Compensates for the loss of neurons
What can L-DOPA do to make dopamine?
Cross the blood-brain barrier and enzymes in neurons convert precursor to dopamine
How does L-DOPA cause relief from Parkinson’s symptoms?
It increases in the brain
What side effects are common with L-DOPA?
Hallucinations, delusions, other psychotic symptoms
What do antipsychotic drugs treat?
Psychotic disorders
What is schizophrenia caused by?
An excess of dopamine- thought to be an excess of mesolimbic dopamine
How do antipsychotic drugs operate?
By interfering with dopamine receptors in the brain- acting as blockers
What receptor do antipsychotic drugs block?
D2
What do antipsychotic drugs reduce operation of?
The dopamine system
What does antipsychotic drugs efficacy hinge on?
Ability to bind to a D2 receptor
What is the side effect of antipsychotic drugs often binding to nigrostriatal pathways by mistake?
Can affect motor functions- very similar to Parkinson’s disease
Why is dopamine implicated in recreational drugs?
Dopamine is involved in producing reward and pleasure
What was cocaine previously used as?
As mental illness treatment and a coca-cola ingredient
When and why was cocaine banned?
In 1922 because people became aware of harmful effects
Short-term effects of cocaine use (7 points)
- Increased energy levels
- Decreased appetite
- Mental alertness
- Increased heart rate and blood pressure
- Constricted blood vessels
- Increased temperature
- Dilated pupils
Long-term effects of cocaine use (5 points)
- High risk of addiction
- Irritability and mood disturbances
- Restlessness
- Paranoia
- Auditory hallucinations
Medical consequences of cocaine use (4 points)
- Cardiovascular (disturbances in heart rhythms, heart attacks)
- Respiratory (chest pain, respiratory failure)
- Neurological (strokes, seizures, headaches)
- Gastrointestinal (abdominal pain, nausea)
How does cocaine increase dopamine levels?
By inhibiting reuptake
What happens when cocaine blocks the transporter opening?
It closes the passage and prevents the transporter from doing its job so dopamine remains high in the synapse
What are amphetamine effects similar to?
Cocaine effects
Amphetamine effects at low doses (7 points)
- Energised and attentive
- Mood improvement
- Reduced appetite
- Increased wakefulness
- Improved reaction time
- Fatigue resistance
- Increased muscle strength
Amphetamine effects at higher doses (3 points)
- Risk of psychosis
- Addiction
- Risk of seizure, stroke, coma, heart attack
What are amphetamines prescribed for?
ADHD, narcolepsy, obesity, depression
Why are amphetamines rarely prescribed now?
As there is a high risk of harm
What do amphetamines cause the neuron to do?
Release more dopamine
What do amphetamines disrupt?
Storage of dopamine into vesicles
With amphetamines, dopamine is released without…
Triggering an action potential
What is the difference between amphetamines and cocaine?
Amphetamines are less euphoric but more stimulating than cocaine
How are amphetamines similar to cocaine? (2 points)
- Increased dopamine signalling in the mesolimbic pathway
- Increased dopamine in the nigrostriatal pathway leads to enhanced basal ganglia and thalamic activity
3 types of drugs that act on the serotonin system
- Selective serotonin reuptake inhibitors (SSRIs)
- MDMA (ectasy)
- Hallucinogens
Example of an SSRI
Prozac
How do SSRIs inhibit reuptake of serotonin?
By blocking transporter
What can more serotonin in the synapse exert influence on?
Other neurons
Are all patients responsive to SSRIs?
No
What is the half-life of fluoxetine (prozac)?
1-4 days
What does MDMA trigger a neuron to do?
Release more serotonin
How does MDMA enter a cell?
Via a passage of serotonergic transporter and triggers release of serotonin
What can MDMA also have effects on?
Norepinephrine and dopamine transporters
What does MDMA indirectly increase?
Hormones such as oxytocin
What is the duration of MDMA action?
4-6 hours
How long does it take for serotonin levels to normalise with MDMA?
Within 24-48 hours
Do hallucinogens act as agonists or antagonists?
Agonists
What can hallucinogens cause?
Distortion in a person’s perception of reality, and can cause changes in thoughts, moods and consciousness
4 examples of hallucinogens
LSD
Psilocin
Mescaline
DMT
What is the discussion regarding hallucinogens and SSRIs?
Whether hallucinogens should be used as a therapeutic treatment when people aren’t responsive to SSRIs
What area does nicotine bind to nicotonic receptors and what does this lead to?
Ventral tegmental area, leads to neural activity that triggers release of dopamine in the mesolimbic pathway
When is nicotine released?
By burning a cigarette
What is smoking a major risk factor? (6 points)
Heart attacks
Strokes
Bronchitis
Cancers
High blood pressure
Alzheimer’s disease
How addictive is nicotine?
Highly
Effects nicotine has on the central nervous system (4 points)
- Pleasure
- Arousal and enhanced vigilance
- Improved task performance
- Anxiety relief
Effects of nicotine on the cardiovascular system (5 points)
- Increased heart rate
- Increased cardiac output
- Increased blood pressure
- Coronary vasoconstriction
- Cutaneous vasoconstriction
Effects of nicotine on other systems (3 points)
- Appetite suppression
- Increased metabolic rate
- Skeletal muscle relaxation
What is the half-life of nicotine?
30 minutes
3 individual differences in elimination of nicotine
Smokers metabolise faster
Gender differences
Genetic differences
What is the most widely consumed stimulant?
Caffeine
What is the caffeine molecule structurally similar to?
Adenosine
What is adenosine?
An inhibitory neurotransmitter that suppresses CNS activities
What does caffeine do to adenosine receptors?
Block them
What can caffeine cause?
Increased release of other neurotransmitters
Effects of caffeine in the cortex at normal doses (4 points)
- Rewarding effect, feel competent
- Alertness, sustained attention, faster thought
- Reduced fatigue, lower need for sleep
- Fine motor coordination, timing accuracy and arithmetic may be impaired
Effects of caffeine with heavy doses (5 points)
- Agitation
- Anxiety
- Tremors
- Panting
- Insomnia
How long does it take for caffeine to be absorbed?
Within 45 minutes
How is caffeine distributed?
Rapidly, circulating through body
How big are caffeine molecules?
Small enough to cross the blood-brain barrier
Why does the half-life of caffeine vary?
According to liver enzyme level
Why are some people more sensitive to caffeine?
They have more efficient metabolism due to enzymes
What is the major psychoactive ingredient in cannabis/marijuana?
Tetrahydrocannabinol
What receptor does cannabis bind to?
The cannaboid CB1 receptor
What does cannabis trigger?
The release of dopamine
What does the mesolimbic dopamine release from cannabis lead to?
Feelings of euphoria
2 potential medical benefits of cannabis
Can act as a painkiller for chronic pain
Can be as effective as opioids
2 consequences of long-term habitual cannabis use
Associated with a decline in memory function
More brain tissue loss the longer cannabis is smoked regularly
What is another word for alcohol?
Ethanol
How is alcohol function at a cellular level understood?
Poorly
How is alcohol a depressant?
It suppresses neural activities in the CNS
What mechanism is involved in alcohol?
Alcohol triggers release of GABA and leads brain into a ‘sedation’ state
What does alcohol increase release in?
Dopamine in the mesolimbic pathway
2 things that alcohol decreases
- Serotonin and noradrenaline: increases risk of depression
- Glutamate: impaired memory
3 things alcohol increases
- Dopamine in the brain reward circuit
- Endogenous opiates
- GABA: sedation, motor impairments
How does alcohol cross the blood-brain barrier?
Easily by diffusion
How is alcohol metabolised?
By liver
What is alcohol transformed to?
Water and CO2
What is Korsakoff’s syndrome?
A chronic memory disorder
2 consequences of Korsakoff’s syndrome
- Persistent learning and memory problems (retrograde and anterograde amnesia)
- Action coordination difficulty
What is heavy alcohol use linked to in the brain?
Brain shrinkage particularly in prefrontal lobes
