Drug Addiction- the science

Question 1

How do drug addictions develop

Answer 1

There are two different systems completely unrelated to one another?

Tolerance- physical dependence
Reward centre- the basis of psychological cravings

Question 2

What is meant by tolerance

Answer 2

Reduced responsiveness to a drug chased by previous administrations

Question 3

What sort of drugs is this seen in?

Answer 3

Opioids, ethanol, barbiturates, benzodiazepines

Question 4

Describe the machinism of tolerance

Answer 4

Drug in—————————— Receptor ————————Drug out

        Less drug absorbed.              Fewer drug receptors 
        Drug metabolised faster.      Less efficient drug receptors 
        More drug excreted

DISPOSITIONAL RESPONSE PHARMACODYNAMIC TOLERANCE

Question 5

Next slide

Answer 5

Extra bit

Question 6

How does tolerance lead to withdrawal symptoms?

Answer 6

The drug has an effect and the body has an adaptive response to compensate. Therefore when you stop the drug the balance swings and the compensatory mechanism becomes no longer compensatory

Question 7

What can be said about the withdrawl effect?

Answer 7

It is always the reverse of the drugs acute effect

E.g. opioid withdrawl= diarrhoea despite opioids producing constipation acutely

Development of to,erase may lead to physical dependence in order to avoid the unwelcome withdrawl effects of the drugs

Question 8

What is the reward pathway?

Answer 8

Neurones project from the ventral tegmetnal area to the nucleus accumbens and prefrontal cortex

When VTA neurones are stimulated dopamine is released
This causes a sensation of reward/pleasure

Question 9

What drugs tap into reward pathways and therefore increase dopamine levels

Answer 9

Heroin increased firing rates of dopaminergic neurones
Amphetamine increases dopamine release
Cocaine inhibits dopamine uptake
Alcohol does it too

This leads to cravings

Question 10

Can you use drugs to treat addiction?

Answer 10

Yes you can use other drugs to knock out the receptors that the reward stimulus acts on, however this reduced other positive stimulus and decreases the individuals quality of life.

Question 11

Is there such a thing as an addictive personality

Answer 11

Yes some people have certain receptors expressed that respond more positively to the pleasurable stimulus and therefore have stronger reward pathways and be more addictive to those compared to other