Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Brain & behaviour > Lecture 4 - Dopamine, Drugs and Reward > Flashcards

Lecture 4 - Dopamine, Drugs and Reward Flashcards

You may prefer our related Brainscape-certified flashcards:
The Brain flashcards
1
Q

What are the 3 Dopamine Pathways in the CNS

A
  1. Nigrostriatal Pathway - Motor Regulation
    - last lecture
    - Substantia Nigra Compacta -> Basal Ganglia
  2. Mesolimbic Pathway - Reward, euphoria, intense emotions
    - VTA -> Nucleus Accumbens
    - this lecture
  3. Mesocortical Pathway - personality, perseverance, compulsion
    - VTA -> Prefrontal Cortex
    - this lecture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Outline the Ventral Tegmental Area (VTA)

*******X

A
  • In midbrain (mesencephalon)
  • Medial (inside of) SNc (substantia nigra)
  • Involved in reward & learning, intense emotions, goal-driven behaviour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What % of Dopaminergic Neurons are in the Mesolimbic and Mesocortical Pathways?
*****

A

50-60% of all dopamingergic neurons

  • there are dopaminergic neurons elsewhere, but most are here
  • Neurons for dopamine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline the Mesolimbic pathway

A
  1. Starts at VTA
    - Dopamine neurons origin is here
  2. Projects mainly to Nuclues Accumbens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does GABA do to Dopamine in mesolimbic pathway

A

GABAergic interneurons within VTA provide long lasting (tonic) inhibition of DA neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What other inputs are them in the Mesolimbic Pathway

*******

A
  1. Glutamate (From cortex)
  2. Acetylcholine (ACH)
  • Involved in Reward signalling, learning and goal-directed behaviour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to the mesolimbic pathway during reward?

*******

A
  1. See an actual reward, or just a cue that indicates a reward will be coming
  2. Increases VTA dopaminergic neuron firing
    or
  3. Lack of actual/ expected reward
  4. decreased firing
  5. Results in increase/ decrease in Nuclues Accumbens Shell DA levels

Important for reward0based learning and goal-driven behaviour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is DA sensitivity linked to?

A
  • Nurture: Linked to personality traits like extraversion, sensation-seeking, reward seeking
  • Nature: just biology
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What did Di Chiara et al (1999) do?

*******

A

Looked at amount of DA in NAc Shell during food and sex

  • when the food box is empty, dopamine isnt firing too much, as soon as food arrives, the dopamine shoots up in the brain
  • During sex there is a massive spike
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Outline when Dopamine spikes in cue and of reward

A
  • When a reward is cued and delivered, Dopamine neurons only respond to the cue eventually (conditioning)
  • When the cue occurs, dopamine peaks, and stays high until reward comes, but is no way near as big of a peak
  • If no reward comes, dopamine drops - can impact mood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is activated when DA Binds to receptor

A

When DA binds to receptor, it activates g-proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does level of dopamine affect the amount of receptors?

A
  1. MORE DOPAMINE = LESS RECEPTORS
    - If there is more dopamine, the brain doesnt need to work as hard to recapture it all
  2. LESS DOPAMINE = MORE RECEPTORS
    - needs to make sure it is all captured as there isnt very many
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does cocaine do to your receptors over time

A

Cocaine increases dopamine, but gives you too much

  • as your brain is used to having loads, it doesnt need many receptors
  • it knows cocaine will come later so dont need many receptors working hard to get as much DA back up
  • therefore has less dopamine as default
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do Opiods, Amphetamines and Cocaine do to this system?

A
  1. Amphetamines do release and removal
  2. Opioids just do Release
  3. Cocaine just do removal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Outline receptor subtypes

A

there are receptor subtypes

  • which are mainly targeted by Dopamine Antagonists
  • when treating psychosis, Sz or delierium - you use dopamine antagonists here, like Anti-psychotics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the 2 enzymes that break down dopamine

A
  • Once DA has done its job, brain breaks it down, loops it back around, metabolises it and reuses it
  1. COMT
  2. MAO
  • Breaks it down into its metabolites - dopamines byproducts that can be used for other things
17
Q

Outline the process of Dopamine crossing the synapse

A
  1. Sodium comes down, merges with vesicle, pushes dopamine down
  2. Depending on the message, is where it goes
    3a. If it goes to: D1 Family of receptors - excitatory, stimulates cAMP, stimulates
    3b. If it goes to: D2 family of receptors - inhibitory, deactivates cAMP, message doesnt continue
    - this is the second messenger process
  3. Can then be: reuptaken if theres too much left, or get broken down by MAO/ COMT
18
Q

What is the receptor that reuptakes dopamine

A

DAT-1 receptor

19
Q

When DA is broken down, by MAO & COMT, what does it get turned into?

A

Homovanillic Acid (HVA)

20
Q

Where do most addictive drugs act on in this system?

*******

A
  • Most addictive drugs cause an increase of DA release from the VTA (Start of the pathway)
  • VTA is the start of both the mesolimbic and mesocortical pathways, so drugs target here
  • Opiods, heroin
  • Amphetamines (ritalin, speed)
  • Benzos
  • Cannabinoids
  • Nicotine, alcohol etc
21
Q

Whats the difference between Chemical and psychological addiction?

A
  1. Chemical Addiction
    - long term impact as brain chemically adjusts, e.g. amount of receptors
  2. Psychological addiction
    - might relieve stress so you want to keep doing it
22
Q

How do amphetamines, cocaine, Nicotine and morphine effect DA levels?

A
  1. Amphetamine
    - Massive hugh spike of dopamine, food was 500, this is like over 1000
    - just doesnt last too long
  2. Cocaine
    - high lasts much longer, but its not as high
  3. Morphine
    - Doesnt have a single spike, but does increase DA over time
    - effects lots of other NT’s so the effects on DA arent as drastic as other drugs
  4. Nicotine
    - does spike, but not as high as others
23
Q

What is the difference between endogenous endorphins and exogenous

A
  1. Endogenous Endorphines - natural endorphines
    - e.g. Dynoprhine
  2. Exogenous
    - what your putting in
    - morphine, heroin, opium etc
24
Q

How do Opiods effect Dopamine

******

A
  • Opiods impact the G-protein coupled receptors which have inhibitory and excitatory subtypes
  • Opiods sit in the receptor and inhibits GABA release
  • As GABA inhibits dopamine, when you inhibit GABA, much more dopamine is released
25
Q

How do Benzodiazepines effect Dopamine

*******

A
  • Similarly to Opiods
  • They dont directly impact the DA neurons
  • But they effeect the GABA receptor, stops GABA from inhibiting DA release
  • GABA communicates to DA neuron with how much DA to fire, when GABA Cant communicate this message, DA doesnt know how much to release, so just releases loads
  • Interact strongly with a1 GABA-A receptors, in GABA interneurons in VTA
26
Q

How does Nicotine effect Dopamine

************

A
  • Indirectly impacts on dopamine
  • Nicotine activates reward pathways - has its own effects, but does impact on DA
  • the VTA projects to the Tegmental Pedunculopontine Nucleus (TPP) - this is a region to do with non-DA-mediated reward
  • In the standard system, GABA goes to TPP to tell it to regulate dopamine. Nicotine slows down GABA, so the TPP doesnt inhibit dopamine as much
  • Nicotines impact on reward can be blocked by lesion/ GABA inhibition of TPP
27
Q

Which pathway will Antagonists have a stronger effect on?

A

Antagonists, like anti-psychotics will have a stronger effect on the D2 pathway (inhibitory), compared to the D1 pathway (excitatory)

28
Q

Outline DA reuptake inhibitors

******

A
  • Can use L-dopa to treat PD, but another treatment is to stop reuptake, we can use a few of these drugs:
  • They inhibit DAT from removing DA from synapse, increasing the amount of DA transmission
    •NDRI’s (Norepinephrine & Dopamine)
    • SDRI’s (Serotonin & Dopamine)
    •SNDRI (Serotonin, Nore, DA)
    •TRI = triple reuptake inhibitor, does all 3

•DRI (Dopamine) - not used that much as it only targets DAT 1 receptor, but other receptors clean up in synapse

29
Q

What is NDRI used for?

*******

A

Depression, ADHD, Narcolepsy, Parkinsons Disease

30
Q

What are examples of SNDRI’s?

A

Cocaine and Amphetamines are both SNDRI’s - inhibit the reuptake of all of these
- leads to euphoria, motor activity, appetite, psychosis

31
Q

How does Cocaine effect Dopamine

A

Cocaine sits right on the reuptake transporter, so none of the dopamine is being cleaned up
- Cocaine has a massive impact, on the reuptake phase, not release phase

  • Different drugs have different effects depending on at which point they impact dopamine
32
Q

What are the 2 variants of COMT breaking down Dopamine

*************

A

After stressor, lots of DA released, COMT has 2 ways of breaking down DA:

  1. Slow form
    - Lots of DA hanging around, clean it slower
    - leads to better concentration, cognitions - perhaps because brain stays more alert for longer
  2. Fast form
    - With less DA
    - Brain goes mental when there is a stressful event, and afterwards brain can settle down quickly

Individual differences in how our brain calms down after a stress

Brain & behaviour (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions