2 - Biochemistry & Physiology of Drug Addiction

Question 1

What does the CNS (central nervous system) consist of? What are each responsible for?

Answer 1

Brain - sensory
Spinal cord - motor

Question 1

What does the PeNS (peripheral nervous system) consist of? What are each responsible for?

Answer 1

Somatic nervous system (voluntary) - sensory & motor
Autonomic nervous system (involuntary) - sympathetic - increase & parasympathetic - decrease

Question 2

What is the amygdala responsible for?

Answer 2

• Emotional & social processing, emotional responses, storage of emotional events
• Creates conditioned response to certain stimuli

Question 3

What is the nucleus accumbens (NA) responsible for?

Answer 3

• Motivation, reward, feeding drug addiction
• Drugs create shortcut to brain’s reward system by flooding NA w/ dopamine

Question 4

What is the hippocampus responsible for?

Answer 4

• Formation of memories & spatial navigation
• Creates memories of rapid sense of satisfaction from drug use

Question 5

What are the different neurons and their responsibilities?

Answer 5

Sensory neuron - carries impulse to interneurons
Interneurons - interpret the impulse
Motor neurons - carries impulse to muscles

Question 6

What happens at the synapse?

Answer 6

1. Action potential (AP) arrives and depolarises presynaptic neuron
2. Ca+ ion channels open, causing influx of Ca+ ions in neuron
3. Influx causes vesicles containing neurotransmitters (NTs) to fuse at end plate of presynaptic neurone
4. NTs released into synaptic cleft
5. NTs bind to receptors on postsynaptic neurone - either excite or inhibit
6. NTs in synaptic cleft recycled during ‘reuptake’. Transporter channel pumps NT back into presynaptic neuron (sometimes NT broken down via enzymes) where it re-enters the vesicles to be used again.

Excite - voltage gated Na+ ion channels open, causing influx. Carries AP over

Inhibit - voltage gated Na+ ion channels remain closed. No influx causes AP to stop

Question 7

What does glutamate do?

Answer 7

• Brain on
• Memory, movement, sensation

Question 8

What does GABA (gamma aminobutyric acid) do?

Answer 8

• Brain off
• Sleep, sedation
• Decrease anxiety and muscle tension

Question 9

What do endocannabinoids do?

Answer 9

Regulates pain, appetite, co-ordination, learning

Question 10

What does serotonin do?

Answer 10

Regulates mood, anxiety, appetite, sleep cycle, temperature

Question 11

What does noradrenaline do?

Answer 11

Increases alertness, attention, blood pressure, mood, anxiety

Question 12

What does dopamine do?

Answer 12

Increase motivation, drive, pleasure, enjoyment

Question 13

What does acetylcholine do?

Answer 13

Regulates sleep cycle, alertness, memory

Question 14

What does adenosine do?

Answer 14

Regulates tiredness & hunger

Question 15

What do endorphins do?

Answer 15

Increase pleasure, reward, decrease pain

Question 16

What does substance P do?

Answer 16

Regulates pain, stress responses

Question 17

What does cholecystokinin do?

Answer 17

When to eat, may manage anxiety

Question 18

How do drugs affect the limbic system at the synaptic level?

Answer 18

• Lock onto neuron, act like a pump, increase NT release
• Block reabsorption of NT, cause unnatural flood of NT

Question 19

How does cocaine, amphetamines & nicotine affect the limbic system?

Answer 19

Cocaine - blocks reabsorption of dopamine, accumulation of dopamine

Amphetamines - stimulate excess release of dopamine, body can’t keep up with reabsorbing it

Nicotine - stimulate release of dopamine, other substance in cigarette smoke blocks monoamine oxidase

Question 20

What is monoamine oxidase?

Answer 20

Enzyme that breaks down dopamine

Question 21

What is the cycle of drug use?

Answer 21

Use drug to increase dopamine (feel high)
Have feelings of pleasure
Nervous systems combats this by lowering dopamine receptors
Must take more drug to feel high
*Start drug to feel high, continue drug to not feel low

Question 22

What is withdrawal? Refer to NTs

Answer 22

• Drug is substituted for body’s natural NTs, so body stops making it naturally/reduces NT receptors
• Body’s physiological response to lack of drug presence (dependence)
• Body’s physiology returns to normal after, stop craving drug

Question 23

What is abstinence?

Answer 23

• Prolonged period of time where addict does not use drugs

e.g.
Drugs use results in decrease in dopamine transporter levels. Methamphetamine users abstain and these levels recover

Question 24

What receptors do opiates act on?

Answer 24

Mu, Delta, Kappa

Question 25

What receptors does nicotine act on?

Answer 25

Nicotinic acetylcholine

Question 26

Are amphetamines an agonist/antagonist? What effect does this have?

Answer 26

Indirect agonist of dopamine by stimulating release

Question 27

What receptors do cannabinoids act on?

Answer 27

CB1 and CB2

Question 28

Is cocaine an agonist/antagonist? What effect does this have?

Answer 28

Indirect agonist of dopamine, inhibits dopamine transporter

Question 29

What receptors does ethanol act on?

Answer 29

GABA agonist, NMDA (N-methyl-D aspartic acid) antagonist

Question 30

What receptors do benzodiazepines act on?

Answer 30

GABA

Question 31

What is drug addiction caused by?

Answer 31

Disorder caused by decrease in NTs and genetics