recreational drugs Flashcards
what are recreational drugs?
any substance used in a non therapeutic manner for its effects on motor, sensory, emotional or cognitive activities
what neurotransmitter is released when exposed to a rewarding stimulus?
dopamine
what pathway is MOST ASSOCIATED with reward?
mesolimbic dopamine pathway
where do dopamine levels rise when reward pathway is activated?
nucleus accumbens
what is another important pathway in the reward pathway?
mesocortical dopamine pathway
where does the mesocortical dopamine pathway originate and travel to?
orignates in ventral tegmental area
travels to cerebral cortex
why is the mesolimbic pathway the main structure of the reward system?
it is consistently activated during rewarding experiences
what is cocaine?
- 15-30 mins of euphoria, energy and alertness
- white powder
what is heroin?
- made from morphine and extracted from opium
- originally used to treat pain and sleeplessness
- white/brown powder
- usually injected
what is amphetamine?
- originally used to treat asthma and sleep disorders, narcolepsy
- white, pink, yellow or grey powder
- snorted, drank or injected
describe the effect of cocaine
- blocks binding site of reuptake receptors
- prevents reuptake of dopamine
- reuptake inhibitor
- excess dopamine in synapse
- overstimulation of post synaptic receptors = initial euphoria
- brain relies on cocaine to maintain high degree of pleasure associated with artificially elevated levels of some neurotransmitters
- increased sensitivity produces depression when withdrawn
describe the effects of heroin
- binds to same receptors as natural opioids
- acts as agonist
- reduces amount of inhibitory neurotransmitters so dopamine flood synapse
- inhibits GABA release- in the reward pathway (especially the VTA) heroin stops the release of GABA, which normally inhibits dopamine release. As a result, dopamine floods the synapse, especially in the nucleus accumbens- part of the brain’s reward pathway.
- brain adapts and relies on heroin for normal function
- withdrawal = low mood, anxiety
describe the effects of amphetamine
- imitates dopamine and diffuses through membrane into terminal button
- forces dopamine out of vesicles
- dopamine is amplified and overbinds, causing intense high
- increases action of norepinephrine by producing rush of adrenaline
- reduces inhibitory effect of glutamate which regulates dopamine levels, making neurons more readily excitable
strength PEE
- compliment of methodology PET
- brain (PET) scans
- directly assess neurotransmission
- compare drug abusing and non drug abusing individuals
- correlate a drugs transit through the brain by monitoring fluctuations of a neurotransmitter
strength PEE
- compliment of methodology fMRI
- monitors metabolic activity in selected brain regions
- each neurotransmitter has a unique distribution among brain regions so locations with heightened or decreased activity levels help provide clues as to the nt involved
- objective and scientific
- controlled conditions
strength PEE
- compliment of methodology lab
- researchers compare individuals with drug exposure history compared to those who dont
- may compare a behaviour or symptom
- high control over extraneous variables
strength PEE
- application
- drugs have been developed to help heroin withdrawal
- naloxone blocks opiate receptors and prevents heroin occupying them
- does not produce euphoria so helps reduce symptoms
- through greater knowledge of drugs and their transmission, effective treatments have been made.
weakness PEE
- generalisability
- higher control over animals as unethical to test on humans
- low generalisation
- siginificant differences in terms of relative size and developments
weakness PEE
- reductionist
- brain and nt functioning are very complex
- one explanation is too simplistic
- too simple to say that drugs inhibit or excite
- ignores social factors of why we initially take drugs
weakness PEE
- criticism of methodology
- brain scans cannot get to level of synaptic transmission
- hard to study mode of action of drugs at synapses
strength PEE and CA
- supporting evidence Olds and Milner
- electrodes in rats brain
- rats press lever and self stimulate
- suggests that there are places in the brain where stimulation is rewarding enough that animals stimulate themselves frequently
- demonstrates the idea of a reward pathway in the brain where desire for pleasure overrides effects of pain
- cannot be generalised to humans
- but good EV controls
strength PEE and CA
- supporting evidence Volkow
- used PET scans
- track dopamine transporter activity in humans during a cocaine induced high
- found when more cocaine occupying dopamine receptors = more intense high
- this supportds the evidence from animal studies
- good spatial resolution
- however invasive and cannot isolate brain areas
weakness PEE
- opposing study
- Alexander
- gave rats morphine hydrochloride for 57 days and when the were brought to the Rat Park they chose the plain water instead of the water laced with morphine
- therefore this suggests that addiction is a result of the environment and not due to biology, suggesting that the explanation of addiction due to solely neurotransmission is incomplete.
