Lecture 34- Drugs and the brain Flashcards
What is a common feature of the drugs that affect behaviour?
-often small molecules (ethanol, nicotine, heroin, valium, LSD, cocaine)
What are the three reasons why people use recreational or abused drugs?
- Pleasure -hedonic drugs are typically addictive and users exhibit tolerance along with addiction(-heroin= exhibit desensitization -shift to the pleasure from the effect to just taking the drug) 2. Novelty or unreality- psychadelic drugs are less commonly considered addictive, provide and experience that is interesting or stimulating 3. some drugs are highly addictive (tobacco) and are not associated with tolerance (no associated change in behaviour execept for seeking the drug)
What aspects of brain function do these drugs affect?
- Behaviour 2. “Mental state”: Motivation, perceived salience, meaning and significance, arousal/vigilance, hedonic experience, emotional states and experiences
Why do these drugs work?
-must mimic some thing natural in our brain -the drugs must imitate neurotransmitters to have an effect -many abused drugs appear to act by modulating neurotransmission at the synapses of the diffuse modulatory systems particularly serotonin, dopamine and noradrenaline
What are drugs with mind altering effects called?
-psychoactive -these can be considered hedonic, psychedelic, stimulant
What is LSD?
-psychedelic drug, hallucinogen -produces distortions of sensations and abnormal associations between sensory experiences -in the 1960s and 1970s it was legal and widely promoted by users as mind expanding -probably a serotonin antagonist but its action is complex and not well understood -LSD is serotonin agonist but sth else must be involved as it doesn’t affect everything in the brain only selective
What are stimulant drugs?
-amphetamines and cocaine -seem to act on aminergic transmission (noradrenaline and dopamine) -however heroin is an opiate and also modulates aminergic systems…
Why are hedonic drugs so addictive?
-the uniting principle of addictive drugs appears to be that they enhance synaptic dopamine by means that dissociate it from normal behaviour control and they act to reinforce their own acquisition -modulating dopamine from VTA to accumbens -efefct on dopaergic transmission= all drugs that are addictive have this effect -increase in dopamine
What is the action of amphetamines?
-
How does cocaine work?
-plasma membrane dopamine uptake transporter blocker -enhances dopamine
What is the majority of communication between neurons like?
-chemical
What are the variations of synaptic arrangements in neurons? (4)
- direct effect on a few
- neuroendocrine transmission= vasopressin, hormones can affect big effect
- want big effect= selective
- single neuron of the dopamine system will make en passant connections with many other neurons
- unusual pattern of connectivity
- change of the state of the brain
Why do drugs work in subtle ways?
-as you wouldn’t want big changes= that could lead to problems! -that is why effect on diffuse modulatory systems (metabotropic channels)
In which diffuse modulatory systems do addictive drugs act most often?
-dopamine system -VTA to nucelus accumbens change is what makes drugs addictive -heroin, nicotine, cocaine…
What can paranoia be a side effect of?
-common in schizophrenic illness -side effect of medication or recreational drugs such as marijuana, and particularly stimulants such as methamphetamine and crack cocaine