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PSYT 301 > Neurobiology of Addiction > Flashcards

Neurobiology of Addiction Flashcards

1
Q

mesocortical DA pathways in the brain + functions (2)

A
  1. VTA -> PFC (executive functions)
  2. VTA -> NAcc (motivation)
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2
Q

what do commonly abused drugs all have in common

A

all stimulate DA transmission one way or another (at synapse level)

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3
Q

ways drugs increase DA signalling and at which part of the neuron (2)

A
  1. activating or disinhibiting VTA DA cell firing (at cell body level)
  2. increasing amount of synaptically released DA (at synaptic level)
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4
Q

ex of drugs that activate or disinhibit VTA DA cell firing (4)

A
  1. morphine
  2. heroin
  3. alcohol
  4. nicotine
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5
Q

ex of drugs that increase DA release at synapse (4)

A
  1. amphetamine
  2. cocaine
  3. methamphetamine
  4. phencyclidine
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6
Q

DA synthesis steps & enzymes (4)

A

phenylalanine -> tyrosine (hydroxyalse)
tyrosine -> L-DOPA (hydroxylase)
L-DOPA -> DA (L-AA decarboxylase)

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7
Q

synaptic DA transmission (9 elements)

A

axon terminal:
1. DA production
2. encapsulation of DA vesicles by vesicular transporters
3. voltage-gated calcium channels opened due to AP (increase in intracellular calcium)
4. vesicular fusion/exocytosis of vesicle + release of DA from vesicle in synaptic cleft
postsyn neuron:
5. DA in synaptic cleft bind to DAr on postsynaptic neuron
6a. activation of 2nd messenger processes
6b. COMT (on postsyn neuron) binds unbound extracellular DA and metabolizes it into 3-methoxytyramine
6c. DAT reuptakes into presyn neuron unbound DA from cleft
7c. DA binds to MAO and metabolizes it into DOPAC (inactivated); DOPAC -> HVA

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8
Q

role of MAO and COMT

A

MAO: inactivates DA (deamination) that is pumped from synaptic cleft via DAT
COMT: binds unbound DA from synaptic cleft and inactivates it (methylation)

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9
Q

amphetamine synaptic transmission (5 elements)

A
  1. vesicular transporter (axon terminal) prefer amphetamine over DA (internalizes more amphetamine molecules than DA)
  2. DA not taken up by vesicles floats around in presynaptic axon terminal
  3. increased [DA] in presynaptic axon terminal reverses the effect of DAT: instead of DA reuptake from synaptic cleft, DA release into synaptic cleft
  4. high amphetamine doses inhibit MAO in presynaptic axon terminal (no DA inactivation)
  5. increased unbound DA in synaptic cleft
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10
Q

cocaine synaptic transmission (3 elements)

A
  1. vesicular transporter not affected
  2. exocytosis not affected
  3. DAT blocked -> prolongs time that DA spends in synaptic cleft, increases DA binding to DAr on postsynaptic neuron
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11
Q

opiate (heroin, morphine) synaptic transmission (no drug vs with drug)

A
  1. no drug: GABA interneuron in VTA releases GABA that binds to DA neurons and stops neuron from firing too fast (inhibition)
  2. with drug: GABA interneuron inhibited (disinhibition) so decreased GABA binding to DA neuron and DA neuron fires faster
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12
Q

where do morphine and heroin bind (2)

A

u receptors on VTA GABA interneurons and NAcc GABA neurons that feedback to VTA cell bodies

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13
Q

what determines the level of sensitization

A

length of the off period

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14
Q

what is acute tolerance

A

decrease of NAcc DA levels and behavioral response with each dose (closely spaced repeated administration; 1-2 per day)

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15
Q

how long does sensitization last

A

months, years (maybe permanent) -> neuroadpative alterations to circuitry mediating actions of drugs

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16
Q

what is cross-sensitization

A

repeated administration of drug #1 will later sensitize to effects of different drug (even if never taken it before)

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17
Q

lever experiments: what happens with DAr blocker

A

animal presses the lever more often: like reducing the dose of the drug

18
Q

liking vs wanting vs learning

A

liking: pleasurable experience from rewards
wanting: motivation (willingness) to pursue rewards (how much effort willing to put to get the reward?)
learning: cues and events associated with rewards acquire predictive and incentive motivational properties

19
Q

motive circuit plays role in (2)

A
  1. ability to predict reward availability
  2. attributing motivational value to cues
20
Q

challenge in studying motive circuit

A

predictive and incentive motivational properties of cues acquired together -> dissociating them is difficult

21
Q

how overcome challenge of studying motive circuit

A

pavlovian conditioned approach -> cue (lever) predicting reward is separated in space from location of reward (separate wanting from liking)

22
Q

2 types of rats observed in PCA

A
  1. sign trackers (want the reward)
  2. goal trackers (like the reward)
23
Q

behavior of STs (3)

A
  1. persistently engage with lever that predicts reward
  2. retrieve reward after lever is retracted
  3. treat the lever as ‘highly desirable’ (has incentive value) -> willing to work for reward
24
Q

behavior of GTs (3)

A
  1. rarely interact with lever
  2. lever gains predictive value (animal waits for the reward where it will be delivered)
  3. don’t find lever attractive
25
Q

conclusions from PCA concerning the lever (2)

A
  1. lever (CS) predictive of reward and evokes conditioned response in STs and GTs
  2. lever has incentive salience only for STs
26
Q

PCA mirrored to drug addicts

A

drug-associated cues have predictive value and incentive value -> drives compulsive drug-seeking behavior

27
Q

NAcc DA release in STs: PCA session 1 vs 5

A

session 1: DA release when get reward (US)
session 5: DA release when press lever (CS)

28
Q

NAcc DA release in GTs: PCA session 1 vs 5

A

session 1: DA release when get reward (US)
session 5: DA release when get reward (and a bit when lever activated)

29
Q

what does differential release of DA in STs vs GTs indicate

A

NAcc DA is necessary to process incentive salience of reward cues, but not to encode their predictive value

30
Q

DAr blockade in STs and GTs

A

impaired acquisition and expression of STs; little effect on behavior of GTs

31
Q

how does stress impact drug use (4)

A
  1. exposure to stressors = risk factor in drug addiction
  2. increases abuse liability of drugs (increases likelihood of engaging in drug-taking)
  3. contributes to escalation from recreational use to compulsive drug-seeking
  4. increases likelihood of relapse in abstinent drug addicts
32
Q

HPA axis

5 elements

A

higher order brain areas (hippocampus & PFC) -> PVN releases CRH -> AP releases ACTH -> adrenal cortex releases CORT -> CORT negative feedback at all levels

33
Q

how does constant stress influence drug taking (3 elements)

A

constant stress -> less effective at turning off HPA axis -> CORT levels stay high -> prolonged brain exposure to CORT (bad) -> influences drug taking

34
Q

relationship between stress, HPA axis and DA transmission (2)

A
  1. NAcc responses to stimulants is sensitized in stressed animals
  2. stimulant-induced DA release in NAcc depends on HPA axis
35
Q

DA release in (a) stressed animals (b) ADX animals (c) animals treated with CRH

A

(a) sensitized response/DA release
(b) low DA release
(c) potentiated DA release (as if stressed)

36
Q

morphological remodeling in PFC following chronic exposure to stress (2)

A
  1. dendritic retraction + spine loss in pyramidal glutamatergic neurons (decreased excitatory input)
  2. dendritic/spine proliferation in GABA interneurons (increased inhibitory input)
37
Q

events that precipitate relapse to drug-taking (sufficient for relapse; wanting) (3)

A
  1. drug itself -> drug-induced relapse
  2. conditioned stimuli -> reward cue-induced relapse
  3. stress -> stress-induced relapse
38
Q

brain circuitry implicated stress-induced relapse (4)

A
  1. VTA DA projection to PFC
  2. NE projection from LTN to CeNA
  3. CRH in BNST
  4. HPA axis
39
Q

meaning of (a) VTA (b) PFC (c) LTN (d) CeNA (e) BNST

A

(a) ventral tegmental area
(b) pre-frontal cortex
(c) lateral tegmental nucleus
(d) central nucleus of the amygdala
(e) bed nucleus of stria terminalis

40
Q

effect of maternal care on HPA axis stress response during adulthood (3)

A
  1. maternally separated when pups -> high stress response + impaired negative feedback when adults
  2. early life adversity -> increased stress responsivity -> increased vulnerability to disease (including to drug addiction)
  3. maternally separated when pups -> willing to work a lot more for reward

PSYT 301 (9 decks)

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