Intra-Accumbens Amphetamine Increases the Conditioned Incentive Salience of Sucrose Reward: Enhancement of Reward “Wanting” without Enhanced “Liking” or Response Reinforcement
Objective: To measure hedonic impact using taste reactivity to assess positive hedonic reaction patterns elicited by sucrose and determine whether intra-accumbens amphetamine increases sucrose 'liking'
Materials & Equipment Checklist
8 items
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Equipment4
not specified • not specified • not specified • not specified
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Protocol Steps
View Abstract
Amphetamine microinjection into the nucleus accumbens shell enhanced the ability of a Pavlovian reward cue to trigger increased instrumental performance for sucrose reward in a pure conditioned incentive paradigm. Rats were first trained to press one of two levers to obtain sucrose pellets. They were separately conditioned to associate a Pavlovian cue (30 sec light) with free sucrose pellets. On test days, the rats received bilateral microinjection of intra-accumbens vehicle or amphetamine (0.0, 2.0, 10.0, or 20.0 μg/0.5 μl), and lever pressing was tested in the absence of any reinforcement contingency, while the Pavlovian cue alone was freely presented at intervals throughout the session. Amphetamine microinjection selectively potentiated the cue-elicited increase in sucrose-associated lever pressing, although instrumental responding was not reinforced by either sucrose or the cue during the test. Intra-accumbens amphetamine can therefore potentiate cue-triggered incentive motivation for reward in the absence of primary or secondary reinforcement. Using the taste reactivity measure of hedonic impact, it was shown that intra-accumbens amphetamine failed to increase positive hedonic reaction patterns elicited by sucrose (i.e., sucrose “liking”) at doses that effectively increase sucrose “wanting.” We conclude that nucleus accumbens dopamine specifically mediates the ability of reward cues to trigger “wanting” (incentive salience) for their associated rewards, independent of both hedonic impact and response reinforcement.
1
Lever press training
Rats were trained to press one of two levers to obtain sucrose pellets
not specifiednot specified
Note: Initial training phase to establish instrumental response
View evidence from paper
“Rats were first trained to press one of two levers to obtain sucrose pellets”
2
Pavlovian conditioning
Rats were separately conditioned to associate a Pavlovian cue (30 second light) with free sucrose pellets
30 seconds per cue presentationnot specified
Note: Separate from lever press training to establish cue-reward association
View evidence from paper
“They were separately conditioned to associate a Pavlovian cue (30 sec light) with free sucrose pellets”
3
Bilateral microinjection
On test days, rats received bilateral microinjection of intra-accumbens vehicle or amphetamine at doses of 0.0, 2.0, 10.0, or 20.0 μg/0.5 μl
not specifiednot specified
Note: Injections were bilateral into nucleus accumbens shell; different doses tested across sessions
View evidence from paper
“On test days, the rats received bilateral microinjection of intra-accumbens vehicle or amphetamine (0.0, 2.0, 10.0, or 20.0 μg/0.5 μl)”
4
Lever pressing test without reinforcement
Following microinjection, lever pressing was tested in the absence of any reinforcement contingency while the Pavlovian cue alone was freely presented at intervals throughout the session
not specifiednot specified
Note: No sucrose or cue-based reinforcement during test; only Pavlovian cue presentation
View evidence from paper
“lever pressing was tested in the absence of any reinforcement contingency, while the Pavlovian cue alone was freely presented at intervals throughout the session”
5
Taste reactivity measurement
Hedonic impact was measured using taste reactivity to assess positive hedonic reaction patterns elicited by sucrose
not specifiednot specified
Note: Measured to determine if amphetamine increased sucrose 'liking' independent of 'wanting'
View evidence from paper
“Using the taste reactivity measure of hedonic impact, it was shown that intra-accumbens amphetamine failed to increase positive hedonic reaction patterns elicited by sucrose”
Subjects / Specimens
Species
rat
Strain
not specified
Age
not specified
Sex
unknown
Weight
not specified
Rats were trained to press levers and conditioned to associate Pavlovian cues with sucrose