Dopamine Function And Addiction

Question 1

How do amphetamines work?

Answer 1

Increase release and decrease uptake via reversal of the uptake pump
Inhibits dopamine breakdown via MAO inhibition

Question 2

What does high dose of systemic amphetamines dots a mouse?

Answer 2

Causes sterotypy - complex movements which are not goal directed)

Question 3

What does low dose amphetamines cause in mice?

Answer 3

Hyperactivity

Question 4

What are the possible explanations for dose dependanct reactions for amphetamines?

Answer 4

Larger release in dopamine within the NAc than striatum

Competition between behaviours

Question 5

What behaviour is produced by amphetamines injection into the NAc?

Answer 5

Hyperactivity

Question 6

What is the effect of amphetamine injection in the striatum?

Answer 6

Stereotypy

Question 7

What is the explanation for hyperactivity as a result of amphetamines?

Answer 7

Environment has become more salient due to increas ein dopamine - manifestation of urge to explore new environment

Question 8

What is operant conditioning?

Answer 8

Animal wil repeats behaviour is the consequence is rewarding e.g. Food, sex, water (driven by motivation)

Question 9

IN the Skinner box what causes an increase in dopamine?

Answer 9

Receiving a reward or a stimulus which has previously been associated with the reward

Question 10

What is the effect of a dopamine antagonist (Pimozide) on number of lever pressings on test days following conditioning?

Answer 10

They will decrease

Question 11

What will happen to number o levers presses of no reward is given after conditioning?

Answer 11

They will decrease

Question 12

What is the process by which an animal will decrease the number of times it presses the lever?

Answer 12

Extinction

Question 13

What is self stimulation?

Answer 13

Animals will work to receive an electrical stimulus of certain brain areas

Question 14

What areas are most effective for promoting self stimulation?

Answer 14

Ventral tegmental area

Median forebrain bundle (pathway between VTA and nucleus accumbens)

Question 15

What other areas (to a lesser extent) will animals self stimulate?

Answer 15

Prefrontal cortex

Nucleus accumbens

Question 16

What are the factors which influence self stimulation?

Answer 16

Drugs/ lesions

Question 17

What can be used to lesion areas containing tyrosine hydroxlase

Answer 17

6-OHDA

Question 18

What does 6-OHDA do when applied to NAc?

Answer 18

Blocks hyperactivity

Question 19

What is the effect on self stimulation on modification of applied current?

Answer 19

Self stimulation is not supported below a certain threshold

As the current increases so will press rate

Question 20

What occurs to press rate on lesions of the median forebrain bundle?

Answer 20

It will be abolished

Question 21

What will happen to press rate on self stimulation on low dose dopamine antagonists?

Answer 21

It will decrease i.e. Pressing lever will have a smaller effect therefore will not do as often

Question 22

What will happen to threshold current on addition of dopamine antagonists?

Answer 22

It will increase. I.e. Current which would normally support self stimulation will increase

Question 23

What is self administration?

Answer 23

Animals will work to receive drug infusions IV or intra cerebrally

Question 24

What drugs will be self administrated intravenously?

Answer 24

Cocaine
Amphetamine
Ethanol
Morphine
Nicotine

Question 25

What drugs will be administered locally for promote self admin?

Answer 25

Amphetamine into the NAc | Morphine into the VTA

Question 26

What factors influence the self administration of cocaine and amphetamine?

Answer 26

Potentiated by dopamine antagonists i.e. Will work harder to overcome blockage of receptors @ low doses of antagonists. At high doses of antagonist all receptors will be block thus behaviour will be attenuated

Question 27

What else attenuates self administration?

Answer 27

6-OHDA lesions of the NAC

Question 28

What is conditioned place preference?

Answer 28

Rats will go to chamber where they receive a reward

Question 29

After condition get a particular chamber with a reward what will happen when a rat is placed into the chamber again? (Without reward)

Answer 29

Rat will go back to chamber where it received the reward. Can measure % time spent in either chamber (old reward chamber vs non reward chamber)

Question 30

What rewards will cause the rat to increase time spent in reward chamber?

Answer 30

Amphetamine D1/D2 agonists Food (amphetamine will enhance the reinforced behaviour)

Question 31

What other things can cause an increase in dopamine within the NAc?

Answer 31

Adverse stimuli e.g. Mild food shock | Release on stimuli predictive of either an adverse or rewarding stimuli

Question 32

What does dopamine increase in the NAc signal?

Answer 32

The salience of a stimuli. Useful for learning. For example, if you find food under a certain type of tree, seeing that tree will increase dopamine level and drive the motivation to eat. Like wise, if a certain see if predictive of a predator seeing that tree will elicit an increase in dopamine

Question 33

How do drugs effect dopamine?

Answer 33

Of the drugs a mouse will self administer all increase dopamine directly or indirectly (NAc>dorsal striatum) All have addictive properties

Question 34

Why is it hypothesised that it is the potentiation of dopamine in the NAc which causes addiction?

Answer 34

The drugs all have different effects e.g. Some are stimulants, hallucinogens and others are depressants. Therefore, their addictive properties are unlikely to be related to their primary pharmacology but their ability to increase dopamine in the NAc

Question 35

what is a common property of addictive drugs?

Answer 35

Increase self stimulation Support self administration Show conditions place preference Enhance reinforced behaviours

Question 36

What do addictive drugs do?

Answer 36

'Hijack' the physiological reward/salience pathway which signals if things are pleasurable or important. This system is essential for reinforcing behaviours of importance

Question 37

What can stimuli associated with drugs do?

Answer 37

Stimuli like watching another person take drugs or seeing a needle will make the person want to take the drug = dependency

Question 38

What are the signs and symptoms associated with dependency?

Answer 38

``` Withdrawal Interests (decrease) Tolerance Harmful consequences Desire/compulsion Control of intake decreases ```

Question 39

Overall wha tis the function of dopamine in the NAc?

Answer 39

Reinforce behaviours which are associated with pleasurable or adverse events through release of dopamine in response to salient stimuli