Addictions Flashcards
What are the main two mechanisms behind why humans abuse drugs?
Tolerance (basis of physical dependence)
Reward centre (basis of psychological craving)
What is tolerance defined as?
Reduced response to a drug caused by previous administration
What is dispositional tolerance?
Tolerance that develops vie allowing less of the drug to reach the receptors that it acts on. Can occur due to:
Less drug being absorbed
Drug being metabolized at a different rate
More of the drug being excreted
What is pharmacodynamic tolerance?
Tolerance that occurs due to the drug having less effect at the receptors it binds to. Can occur due to:
Change in receptor number (fewer)
Change in receptor efficiency (eg. less cAMP produced)
How does the development of tolerance lead to withdrawal symptoms and dependence?
- Individual takes the drug and this alters the homeostatic balance of some transmitter in the brain
- The body senses this alteration and produces an adaptive response that puts the body back into homeostasis with the presence of the drug
- The individual then stops taking the drug which puts the body out of homeostasis once again.
- The person craves and depends on the drug to get back to homeostasis, until the body can produce yet another adaptive response
How does the withdrawal effect often relate to the acute effect of a drug?
The withdrawal effect is often the opposite of the acute effect
Due to development of tolerance, the drug pushes homeostasis to the left, the body balances it back to centre, then stopping the drug sends the body to the right
Eg Cocaine: acute effect is elevated mood, withdrawal effect is depressed mood
What is dependence in relation to tolerance of a drug?
Dependence is the continued adminsteration of a drug to avoid the withdrawal effects that have been developed through building tolerance to a drug
What is the anatomical location of the reward pathway in the brain?
Neurones project from the ventral tegmental area, on to the nucleus accumbens and finally into the prefrontal cortex
How do drugs influence the reward pathway?
They tap into the reward pathway by increasing dopamine levels
This produces the psychological phenomena of craving
How does heroin influence the reward pathway?
Heroin increases firing rate of dopaminergic neurones
How does amphetamine influence the reward pathway?
It increases dopamine release
How does cocaine influence the reward pathway?
Inhibits the uptake of dopamine
What are some of the reasons you shouldn’t stimulate your reward centre with drugs?
Societal - most drugs are illegal and therefore taking drugs requires involvement in illegal activity
Motivational / brain functioning - if you stimulate your brain with drugs all the time you will have less of a drive to stimulate it in other ways (sex / food)
Is there such thing as an addictive personality?
Some studies have found links between genetic variations and predisposition to addiction
Some people may be genetically predisposed to addiction due to the exaggerated response of their reward system to stimulants
By what mechanism does cocaine stimulate the reward pathway?
Monoamine reuptake inhibitor
So increases synaptic levels of dopamine, serotonin and noradrenaline
