introduction to addiction and the brain

Question 1

define neuropharmacology

Answer 1

branch of pharmacology that deals with the action of drugs on the nervous system

Question 2

what is a neurotransmitter?

Answer 2

naturally occurring chemical that carry chemical signals (messages) from one neuron (nerve cell) to the next target cell

Question 3

define psychotropic

Answer 3

drugs that affect a person’s mental state

Question 4

identify 4 classic neurotransmitters involved in addiction

Answer 4

• dopamine
• noradrenaline
• serotonin
• acetylcholine

Question 5

what is another name for serotonin?

Answer 5

5-hydroxytryptamine, 5-HT

Question 6

what drugs release neurotransmitter dopamine?

Answer 6

amphetamines
cocaine

Question 7

what drugs release neurotransmitter noradrenaline?

Answer 7

amphetamines
cocaine

Question 8

what drugs increase serotonin?

Answer 8

ecstasy (MDMA)

Question 9

what drug activates acetylcholine receptors?

Answer 9

nicotine

Question 10

what is chemical transmission?

Answer 10

the way a signal gets from one neuron/brain cell to the next

chemical transmission relies on number of different signalling pathways and chemical systems

Question 11

why do we have neurotransmitters?

Answer 11

due to the need for communication within the brain and the rest of nervous system

neuron and nerve cells need to communicate with eac hother

Question 12

describe the nerve transmission process

Answer 12

dendrites -> cell body (soma) -> axon -> axon terminal

• neural signals travel electrically along nerve fibres
• neurotransmitters cross a synaptic gap/cleft between nerve cells to reach next neuron
• crosses synaptic cleft through process of diffusion

Question 13

what are neurotransmitters stored in?

Answer 13

synaptic vesicles

Question 14

how are neurotransmitters received at end of axon terminal?

Answer 14

• receptors
• these are specially configured to receive and be activated by the neurotransmitter that is released
• this unlocks a postsynaptic response as an ‘agonist’

Question 15

what is similar about psychotropic drugs and neurotransmitters and how does this affect receptors?

Answer 15

• psychotropic drugs and neurotransmitters have similar chemical structures
• meaning they can activate or block receptors that are intended to recognise brain’s own neurotransmitters

Question 16

what is it meant by ‘AGONIST’ with regards to neurotransmitters?

Answer 16

• AGONISTS are substances that bind to synaptic receptors
• these INCREASE the effect of neurotransmitter
• has the net effect to increase neurotransmission (as a direct or indirect agonist)

Question 17

what is it meant by ‘ANTAGONIST’ with regards to neurotransmitters?

Answer 17

• ANTAGONISTS are substances that bind to synaptic receptors
• these DECREASE the effect of a neurotransmitter (these block receptor)
• has the net effect to decrease neurotransmission (as a direct or indirect antagonist)

Question 18

what do ‘autoreceptors’ do?

Answer 18

• found presynaptically
• act like thermostats
• regulate neurotransmitter release and neuronal firing at neuron terminal and cell body
• neurotransmitters/drugs acting here can reduce further release at the termal so further neurotransmission is reduced

Question 19

what effect can drugs have on synaptic transmission?

Answer 19

• can have a net positive effect (as direct or indirect agonist)
• can have a net negative effect (as direct or indirect antagonist)

Question 20

give an example of drug action that acts as an agonist

Answer 20

amphetamines

stimulate release of dopamine and noradrenaline

Question 21

give an example of drug action that acts as an antagonist

Answer 21

cocaine

blocks the reuptake of dopamine and noradrenaline

Question 22

What are the short term effects of MDMA/Ecstasy?

Gerra et al. (2000) study looking at the effects of MDMA/ecstasy

Answer 22

• drug increases serotonergic (5-HT)
• serotonergic = affecting serotonin neurotransmitter
• drug increases levels of serotonin

Question 23

What is the suggested long term effect of MDMA/Ecstasy?

Gerra et al. (2000) study looking at the effects of MDMA/ecstasy

Answer 23

• evidence that serotonin can become depleted
• indicating neurotoxicity (altering of normal activity of nervous system)
• results in cell death in serotonergic pathways

Question 24

Outline Gerra et al. (2000) study looking at the effects of MDMA/ecstasy

Answer 24

• uses an indirect measure to look at effect
• looks at measuring serotonergic function indirectly
• done by issuing challenge test
• fenfluramine is a drug that increases serotonin release
• increased serotonin has effect on pituitary gland –> this is shown as hormonal change (specifically prolactin response
• plasma prolactin is looked at to measure the effect of fenfluramine
• a normal response should show that an increase of fenfluramine would results in an increase in plasma prolactin as fenfluramine increases serotonin which increases hormonal response of prolactin

Question 25

Outline findings of Gerra et al. (2000) study looking at the effects of MDMA/ecstasy

Answer 25

'normal' volunteers - show an increased prolactin response to fenfluramine - consistent with what was expected of normal response 'MDMA' users - showed a reduced prolactin response to fenfluramine - suggests that MDMA users serotonergic function is depressed - additionally, reduced response to prolactin persists in ppts who previously used MDMA but do not presently - suggests long term effects of long term use of MDMA - evidence consistent with neurotoxicity and death of pathways --> if change was functional, some recovery would be expected when drug use stops but this is not the case

Question 25

Outline findings of Gerra et al. (2000) study looking at the effects of MDMA/ecstasy

Answer 25

'normal' volunteers - show an increased prolactin response to fenfluramine - consistent with what was expected of normal response 'MDMA' users - showed a reduced prolactin response to fenfluramine - suggests that MDMA users serotonergic function is depressed - additionally, reduced response to prolactin persists in ppts who previously used MDMA but do not presently - suggests long term effects of long term use of MDMA - evidence consistent with neurotoxicity and death of pathways --> if change was functional, some recovery would be expected when drug use stops but this is not the case

Question 26

Outline Miczek & Mutschler (1996) study looking at the effects of social stress in lab animals

Answer 26

- lab animals used - social stress brings about physiological response - rats trained to respond by pressing level for cocaine or food reward - before social stress introduced, rats responded more for lever - social stress introduced - social stress manufactured by placing an 'intruder' which was another male rat - intruder would attack (wire mesh placed to prevent injury) - lasted 60 minutes - after social stress, rats showed increase response for cocaine but not for food reward - shows selective effect of social stress on cocaine-reinforced responding - shows drug as very powerful reward

Question 27

How does Miczek & Mutschler (1996) rat study apply to addiction in humans?

Answer 27

- suggests role of stressful life events in relapse of human drug users