Reward, reinforcement and drugs of abuse

Question 1

What is reward?

Answer 1

Subjective - the feeling of happiness or well-being and is linked to euphoria.

Question 2

What is reinforcement?

Answer 2

This is performing a behaviour in order to obtain a stimulus such as a reward.

Question 3

What can rewarding substances and behaviours lead to?

Answer 3

Addiction.

Question 4

What is addiction/drug dependence?

Answer 4

The desire to seek/experience drug effects that take precedence over other needs and dominates the lifestyle. Harm to yourself and the community is caused.

Question 5

What is psychological dependence?

Answer 5

Craving, compulsion, loss and control due to the addiction.

Question 6

What is physical dependence?

Answer 6

When stopping a drug causes a withdrawel syndrome.

Question 7

What is tolerance?

Answer 7

When continued use of a drug results in the need for increasing doses for equivalent effect.

Question 8

What is withdrawel?

Answer 8

Physical symptoms as a result of not taking drugs.

Question 9

What were the experiments done with Olds and Milner in 1954?

Answer 9

They identified brain sites that were rewarding and reinforcing in rats and stimulated these areas and observed the behaviours in the rats.

Question 10

What was found from the experiments with Olds and Milner?

Answer 10

If the rats were allowed to self deliver stimulation they preferred this to food, water and sex and would cause stimulation to levels of collapse.

Question 11

What is the biological basis behind reward?

Answer 11

Pathways that contain dopamine, noradrenaline and 5HT are linked to reward.

Question 12

What is the most preferred pathway for the rats?

Answer 12

The dopamine pathway.

Question 13

What happened if rats were given a D1/D2 antagonist?

Answer 13

They no longer seeked the reward.

Question 14

What is the name of the behaviour the rats completed?

Answer 14

Intra-cranial self-stimulation (ICSS)

Question 15

What did the ICSS result in?

Answer 15

Dopamine release in the accumbens.

Question 16

Where are the most rewarding sites found?

Answer 16

The medial forebrain bundle.

Question 17

What are the most sensitive areas in the MFB?

Answer 17

THe ventral tegemental area and the nucleus accumbens.

Question 18

What is the dopamine pathway in the accumbens thought to be?

Answer 18

The underlying system providing the rewarding stimulus.

Question 19

What was found in monkeys are the tegmental area?

Answer 19

If a light stimulus was provided before a rewarding stimulus was given, even just seeing the light caused the tegmental area to fire action potentials after repetition. If there was light but no reward there is inhibition, resulting in disappointment.

Question 20

What was a similar experiment done with rats?

Answer 20

If they were given intravenous drugs to self-administer, they self administered to death.

Question 21

What drugs used by humans will be self-administered by rats?

Answer 21

Amphetamine, cocaine, nicotine, ethanol, heroin, codeine, morphine, methadone, PCP, THC, caffeine, diazepam and ecstasy.

Question 22

What drug used by humans will not be self-administered by rats?

Answer 22

LSD.

Question 23

What happens is dopamine neurons are lesioned?

Answer 23

This was prevent self-administration of the drugs.

Question 24

Where do recreational drugs release dopamine?

Answer 24

In the accumbens.

Question 25

What drugs do not cause increased dopamine in the accumbens?

Answer 25

Diazepam and LSD.

Question 26

What drugs cause increased dopamine in the accumbens?

Answer 26

Amphetamine, cocaine, nicotine, alcohol, heroin, coedine, morphine, methadone, PCP, THC and caffeine.

Question 27

Why doesn’t diazepam cause increased dopamine in the accumbens?

Answer 27

Rats still seek it out but there is a different mechanism behind this.

Question 28

How does amphetamine cause increased dopamine levels in the accumbens?

Answer 28

It gets taken up into the terminal and causes more dopamine to be released from vesicles.

Question 29

How does cocaine cause increase dopamine levels in the accumbens?

Answer 29

It blocks the reuptake of dopamine into the terminals.

Question 30

How do opiates such as morphine, heroin and methadone cause increase dopamine release in the accumbens?

Answer 30

THey inhibit GABA neurons via mu receptors and inhibit gaba release from nerve terminals. They disinhibit projection neurons which causes increase firing.

Question 31

How does cannabis cause increased dopamine release in the accumbens?

Answer 31

It acts similarly to heroin and opiates. The THC inhibits GABA neurons via CB1/CB2 receptors which causes increase excitability. They are similar but not as powerful as opiates.

Question 32

How does alcohol cause increase dopamine release in the accumbens?

Answer 32

It increases the excitation of the VTA neurons by blocking potassium channels, reduces action potential repolarisation, causes increased firing and increases dopamine release.

Question 33

What other actions does alcohol have?

Answer 33

It decreases after-hypolerpolarisation, it is a GABA allosteric modulator, it is an NMDA receptor antagonist and a calcium channel antagonist.

Question 34

How does nictotine act to increase dopamine at at the accumbens?

Answer 34

It acts at multiple sites via a nicotinic ACh receptors. It depolarises and excites VTA neurons and indirectly excites VTA neurons by increasing glutamate release. Increased firing results in increased DA release in the Nucleus accumbens and also indirectlyexcites the accumbens spiny neurons by glutamate release.

Question 35

What are natural releases of dopamine?

Answer 35

Eating nice food, sex, music.