Flashcards in Principles Of Neuroscience Lecture 33 Drugs And The Brain Deck (37)
What are the general features of psychoactive drugs?
Resemble endogenous chemicals
What are some common psychoactive drugs?
What are the two reasons that psychoactive drugs are used?
1. Pleasure - Hedonic drugs
2. Novelty - Psychadelic drugs
What are the features of hedonic drugs?
- tolerance exhibited by the users
What are the features of psychedelic drugs?
- not as addictive as hedonic drugs
- not associated with tolerance
What is interesting about tobacco?
It is highly addictive, however, the users do not show tolerance
What aspects of brain function are affected by psychoactive drugs?
- psychomotor agitations
2. Mental function
Which functions of the PFC are altered by drugs?
- Perceived salience
- Emotional state
- Meaning and significance
- and vigilance
- Hedonic experience
How do psychoactive drugs act?
Since they are small and lipophilic, they can cross the blood brain barrier
There are chemical homologous in the brain with their own receptors. Drugs bind to see receptors and alter the kinetics of neurons
Describe what the research of opiate receptors lead to
Researchers were looking for the opioid receptor
Once they found it, they discovered the endogenous compound; endorphins
What are the different classes of neurotransmitters?
Amino acids: glutamate, glycine, GABA
Small amines: noradrenaline, acetylcholine
What systems in the brain do psychoactive drugs work on?
The neuromodulatory systems
What is the effect of LSD?
How does it act in the brain?
LSD causes hallucinations, "mind expanding" experiences
How do amphetamines and cocaine act in the brain?
These hijack the dopamine and noradrenaline systems
Which general features seems to be always seen in addictive drugs?
Give an example
Enhancement of the dopaminergic signal transduction
Eg. nicotine acts on nAChR, leading to increased dopamine
What are the four different types of connections between neurons?
Which does the neuromodulatory system use?
a. Simple - vision and motor control
b. Endocrine (big effect)
c. Amplification - ANS, preganglionic neurons controlling blood flow
d. Highly divergent (en passant) - the neuromodulatory systems
Describe the subtle action of drugs
The drugs bind to the metabotropic receptors in the neuromodulatory systems and subtle alter the kinetics and excitability of the neuron
They do not vastly change the activity of the neurons
Which sort of things does the serotonin system affect?
What is the nucleus in the serotonin neuromodulatory system?
Raphe nucleus in the brain stem
What is the nucleus in the dopamine neuromodulatory system?
Substantia nigra and Ventral tegmental area in the brain stem
Describe the action of cocaine on one of the neuromodulatory systems
Cocaine increases the concentration of dopamine at the synapse in the nucleus accumbens
Describe the action of heroin and nicotine on one of the neuromodulatory systems
Heroin and nicotine increase the action of the dopamine neurons in the VTA
What are the different causes of hallucinations?
- Side effect of medication
- Crack cocaine
Describe how seemingly different drugs can have similar effects
Marajuana and crack cocaine both cause hallucinations, even thought they are very different in function
Why is alcohol the biggest drugs problem?
It accounts for the most reduction in life span and deaths as well as it costs 4.5 billion dollars, over twice the cost of all illicit drugs
Describe the model of the effect of alcohol
Cause: volume drunk and patterns of drinking
Acute effects: intoxication -> injury, acute social and psychological problems
Chronic effects: dependence and toxicity -> chronic injury and social and psychological problems
What are some chronic diseases caused by alcohol?
Neuro psychotic diseases (epilepsy, unipolar depression, PTSD, schizophrenia)
Diseases associated with drinking during pregnancy
What is the aetiology of FAS?
Alcohol crosses the blood brain barrier of the barrier; causing damage
What are the external features of FAS?
Flattened mid face
Low nose arch
Smooth upper lip
Small eye openings
What are the internal features of FAS?
Small brain, large gap between the hemispheres
The prefrontal cortex is the most affected
How is FAS diagnosed?
1. Decreased cognitive function:
- concentration, impulsiveness
- learning disabilities
- maths skills
- social perception
- IQ below the 3rd pcentile
2. Anatomical features of the brain
- callosal dysgenesis
- migration abnormalities
Where does alcohol act in the brain?
On GABA receptors (different site to benzodiazepine)
What are the acute effects of alcohol acting in the brain? (4)
1. Potentiate as well as antagonise GABA's effects
2. Decrease GABA receptor density in the brain -> anxiety
3. Increases glutamate receptors in the hippocampus -> memory affected
4. Stimulates the release of serotonin (mood), endorphins (cravings) and dopamine (addiction)
What are the chronic effects of alcohol on the brain?
- Reduced brain volume, especially the white matter and PFC
- Thiamine deficiency
- Liver disease (hallmark of complicated alcoholics)
Describe what is meant by the coherent effects of psychoactive drugs
These drugs somehow do not cause massive disorganisation of brain activity, but have coherent, subtle effects on the brain
Give examples of why neurotransmitters are not solely responsible for functions of the brain
Serotonin not solely responsible for mood
Dopamine not solely a molecule that produces reward and pleasure