Psychoactive drugs Flashcards
What effects do psychoactive drugs cause?
They cause profound changes in perception, mood and behaviour
What are some other terms used to describe psychoactive drugs?
Psychotomimetic
Psychotropic
Psychoactive
(these all cause mind alterations and hallucinations)
Where do many hallucinogens occur from?
many are naturally occuring
Name 2 naturally occuring hallucinogens?
Ayahuasca
Peyote
Tell me about Ayahuasca (caapi)
obtained from?
Its active constiuent?
What recpetors does it have an effect on?
- Obtained from vines
- The active constituent is harmaline
- Gives an hallucinogenic effect
- The harmala alkaloid are psychoactive in humans
- interact with 5-HT signalling in the brain and is a acetylcholinesterase inhibitor
Tell me about peyote
Why is it used?
What is it obtained from?
Whats the active constituent?
What receptors does it interact with?
- Peyote is used by native Americans in religious ceremonies
- This is a cactus.
- The active constituent is Mescaline
- This is a hallucinogenic alkaloid
- Binds to and activates the serotonin 5-HT2C receptors
- Also stimulates the dopamine receptors, but it’s unclear whether it possesses dopamine receptor agonist properties or initiates the release of dopamine).
Compare the following hallucinogens with their dose, duration of action and therefore potency?
Psilocybin
Mesacaline
Lysergic acid diethylamide (LSD)
Which ones are natural and which ones are synthetic?
Potency (least to most)
Mesacaline > Psilocybin > LSD

When was LSD first synthesised and why was it created?
Why was it synthesised? 10th century there were roughly 40,000 victims in France of ergotism and they suffered from gangrene. It was due to the rye from their rye bread.
What is LSD a derivative of?
Naturally occuring ergot alkaloids
This is a fungus that grows on rye and less commonly wheat e.g., compound ergotamine is an examples of an ergot alkaloid
What type of effects do ergot alkaloids cause?
In the past, due to the effects of the ergot’s what did they try and use them for?
Peripheral Vasocontriction
The derivatives were sought which could be used to control post-partum bleeding
When was LSD first synthesised and who did this?
In 1943, Albert Hoffman, working for Sandoz, was the first to synthesise LSD and the first to ingest it
What type of effects was recorded to have been experienced by LSD?
Explain a bit about each of these effects
- Somatic (mild autonomic changes of mydriasis- pupil dilation, tachycardia, tachypnoea- fast breathing, hyperthermia- high body temperature, hypertonia- too much muscle tone so the limbs are hard to move and hyperglycaemia- high glucose levels)
- Perceptual (5HT2A receptors plays a crucial role in changes in perception and thought)
- Psychological (stimulates serotonin-2A or 5HT2A receptor which is involved in mood and cognition)
- Synaesthesia is the mixing of the senses (LSD bring about this)
What two hallucinogens is there a cross tolerance between?
What does this mean?
What does this suggest?
There is a cross tolerance between Mescaline and LSD
Cross-tolerance can be defined as a specific type of drug tolerance that is formed through continued use of another drug with similar effects
·This suggests that both psychotomimetic act at the same class of receptor site

The structure of LSD, mescaline and 5-HT are all what type of structures?
These structures are similar as are all indoleamine like structures
Indolamines are a classification of monoamine neurotransmitter, along with catecholamines and ethylamine derivatives.
Why does tolerance come about in the brain?
Brain undergoes neuroadaptation and downgrades the pathways that mediates the effects of the drug. The brain tries to rebalance the signalling network in the body. Hence how tolerance comes about
What did early in vitro pharmacological studies show about LSD interactions?
Showed that LSD interacts with 5-HT receptors in the peripheral vasculature
What does LSD act as in the periphery?
It acts as a 5-HT2 receptor antagonist
What receptors mediate the effect of LSD on the vasculature smooth muscle?
5HT2 receptors
What does LSD decrease the levels of?
LSD decreases the levels of 5-HT metabolites when adminstered to rate
Explain neurotransmitter turnover and what this means
Explain this process involving LSD
Neurotransmitter turnover:
In the brain theres 5-HT synases that release 5-HT which acts on post synaptic neurons. Post-synaptic receptors of 5-HT and pre-synaptic autoreceptors of 5-HT which regulate signalling through this network. 5-HT can bind to the autoreceptors and inhibit further 5-HT release. A negative feedback mechanism.
With an antagonist like LSD, it can act at the pre- and post- synaptic 5-HT2 receptors. Which leads to more 5-HT release metabolites CSF plasma urine. However, LSD was found to decrease the level of metabolites hence LSD is a 5-HT2 receptor agonist.
In the brain LSD acts as a 5-HT receptor agonist/ partial agonist
Where does LSD act in the brain?
What does it effect?

How does LSD alter perception
Think about what neurons it has an effect on
- Look at reticular activating system as this deals with the input of the modality specificity input
- LSD decreases the firing rate of raphe neurones (5-HT1A receptor)
- In the raphe cell body has local projections (dendrites) which can release 5-HT (dendritic release)- usually released at nerve ending of axonal projection. The dendritic release can act on the 5-HT1A receptors. If LSD is applied, the firing rate of these neurons is decreased as it acts on the 5-HT1A receptors.
- Another proof that LSD is an agonist at 5-HT receptors
- Raphe neurons send extensive projection to the forebrain

Even though LSD and Mescaline are shown to have cross tolerance which suggests they act on the same neurotransmitter pathways, how is the effect on perception different between these two hallucinogens?
…but investigation of further classes of hallucinogens showed that they did not all exert this effect (e.g., mescaline).
This firing effect was not done by mescaline; and other effects that LSD caused on 5-HT receptors.
Tell me about the results and experiments done on rats when scientists lesion the raphe nucleus of rats
Lesioning the raphe nucleus in rats: they can still discriminate between saline and LSD. Suggests that Raphe nuclei is involved with LSD but not the hallucinogenic properties of the drug
The below technique is used to know when rats are hallucinating:
































