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Nucleus Accumbens Shell and Core Dopamine modifications during operant responding for sucrose
No full textNUCLEUS ACCUMBENS SHELL AND CORE DOPAMINE MODIFICATIONS DURING OPERANT RESPONDING FOR SUCROSE
No full textNatural and pharmacological rewarding primary stimuli potentiated mesolimbic dopamine (DA) transmission. Stimuli conditioned (CS) to these rewards (food, sex, drugs of abuse) (US), are essential to support the motivated behaviour, and it is well known that drugs-CSs increased mesolimbic DA. Much discrepancies exist about the impact of food-CSs on nucleus accumbens (NAc) DA. In particular it has been reported that after classical conditioning paradigm, NAc-shell DA shows responsiveness to food US, but it is unresponsive to food-CS, while NAc-core DA is both affected by food-CS and US.
The aim of our study was to clarify the role of NAc DA in the responsiveness to CS and to US using a self-administration paradigm (FR1 and FR5).
Coupling the microdialysis technique to this paradigm we have studied DA transmission in NAc-shell and core during: 1)sucrose pellets seeking behavior, 2)conditioned cues exposure and 3)non-contingent presentation of sucrose pellets.
The main finding of our study was that NAc-shell DA has been activated not only by the conditioned cues but also by food after the instrumental conditioning, and that when both stimuli are presented in the same moment the increase of DA is strengthened and prolonged.
We also found that during the acquisition process DA in the shell, but not in the core, increased in parallel to the progress of the training process.
We can conclude that DA in the NAc-shell plays an important role on the acquisition and expression of motivated behavior in food consumption
Differential activation of accumbens shell and core dopamine by sucrose reinforcement with nose poking and with lever pressing
No full textIn order to investigate the role of modus operandi in the changes of nucleus accumbens (NAc) dopamine (DA) transmission in sucrose reinforcement, extracellular DA was monitored by microdialysis in the NAc shell and core of rats trained on a fixed-ratio 1 schedule to respond for sucrose pellets by nose poking and lever pressing respectively. After training, rats were tested on three different sessions: sucrose reinforcement, extinction and passive sucrose presentation. In rats responding by nose poking dialysate DA increased in the shell but not in the core under reinforced as well as under extinction sessions. In contrast, in rats responding by lever pressing dialysate DA increased both in the accumbens shell and core under reinforced and extinction sessions. Response non-contingent sucrose presentation increased dialysate DA in the shell and core of rats trained to respond for sucrose by nose poking as well as in those trained by lever pressing. In rats trained to respond for sucrose by nose poking on a FR5 schedule dialysate DA also increased selectively in the NAc shell during reinforced responding and in both the shell and core under passive sucrose presentation. These findings, while provide an explanation for the discrepancies existing in the literature over the responsiveness of shell and core DA in rats responding for food, are consistent with the notion that NAc shell and core DA encode different aspects of reinforcement
Nucleus Accumbens and Prefrontal Cortex Dopamine modifications during operant responding for sucrose
No full textMesolimbic dopamine (DA) plays a key role in the responsiveness to rewarding properties of natural and pharmacological stimuli. These stimuli are able to give rise to motivated behavior, and it is well known that conditioned stimuli (CS), linked with rewards (food, sex, drugs of abuse) (US), are essential to support it.
The purpose of this investigation was to clarify the role of mesolimbic and mesocortical DA in the responsiveness to food and food-CS using an instrumental conditioning paradigm with fixed-ratio (FR) 1 (1 nose poke corresponds to 1 sucrose pellet) or 5 (5 nose pokes correspond to 1 sucrose pellet).
We have coupled a self administration paradigm with microdialysis technique to study DA transmission in the NAc shell and core and in the prefrontal cortex during: 1) sucrose pellets seeking behavior, 2) extinction phase and 3) non-contingent presentation of sucrose pellets.
The main finding of our study was that NAc shell DA has been activated not only by the conditioned cues but also by food after the instrumental conditioning, and that when both stimuli are presented in the same moment the increase of DA is strengthened and prolonged.
We can conclude that DA in the NAc shell plays an important role on the acquisition and expression of motivated behavior in food consumption
DOPAMINE RESPONSIVENESS IN THE NUCLEUS ACCUMBENS SHELL AND CORE DURING ETHANOL AND SUCROSE SELF-ADMINISTRATION
No full textEthanol is a psychoactive compound of several beverage abused by humans and it is well known that, as well as other drugs of abuse, increases dopamine (DA) transmission preferentially in the nucleus accumbens (NAc) shell.
The aim of our study was to investigate by microdialysis the role of the NAc shell and core DA in the response to ethanol and to ethanol-conditioned stimuli (ethanol-CS) using an instrumental conditioning paradigm with fixed-ratio 1 (FR1).
Rats were trained to acquire sucrose and ethanol oral self-administration under a FR 1 paradigm (1 nose poke corresponds to 0.25 ml administration of 20% sucrose or 10% ethanol in 20% sucrose solutions).
We found that oral ethanol, either self-administered or given passively, produces an increase of DA transmission in the shell and in the core, strengthened during the self-administration session, while ethanol-CS increased DA preferentially in the NAc shell. Sucrose oral self-administration and its conditioned cues affects DA exclusively in the shell, but the passive administration increases DA in the shell and in the core.
These data suggest that the two compartments of the NAc are differently implicated in the responsiveness to natural and to pharmacological rewards. While DA transmission in the NAc shell seems to play a key role in the operant responding for both sucrose and ethanol, the DA core appears to be more involved in the responsiveness to ethanol
Changes of dopamine transmission in the nucleus accumbens shell and core during ethanol and sucrose self-administration
No full textEthanol is a psychoactive compound of several beverage abused by humans and it is well known that, as well as other drugs of abuse, increases dopamine (DA) transmission preferentially in the nucleus accumbens (NAc) shell.
The aim of our study was to investigate by microdialysis the role of the NAc shell and core DA in the response to ethanol and to ethanol-conditioned stimuli (ethanol-CS) using an instrumental conditioning paradigm with fixed-ratio 1 (FR1).
Rats were trained to acquire sucrose and ethanol oral self-administration under a FR 1 paradigm (1 nose poke corresponds to 0.25 ml administration of 20% sucrose or 10% ethanol in 20% sucrose solutions).
We found that oral ethanol, either self-administered or given passively, produces an increase of DA transmission in the shell and in the core, strengthened during the self-administration session, while ethanol-CS increased DA preferentially in the NAc shell. Sucrose oral self-administration and its conditioned cues affects DA exclusively in the shell, but the passive administration increases DA in the shell and in the core.
These data suggest that the two compartments of the NAc are differently implicated in the responsiveness to natural and to pharmacological rewards. While DA transmission in the NAc shell seems to play a key role in the operant responding for both sucrose and ethanol, the DA core appears to be more involved in the responsiveness to ethanol
Changes in dopamine transmission in the nucleus accumbens shell and core during ethanol and sucrose self-administration
No full textEthanol, like other substances of abuse, preferentially increases dopamine (DA) transmission in the rat nucleus accumbens (NAc) following passive administration. It remains unclear, however, whether ethanol also increases NAc DA transmission following operant oral self-administration (SA). The NAc is made-up of a ventro-medial compartment, the shell and a dorso-lateral one, the core, where DA transmission responds differentially following exposure to drugs of abuse. Previous studies from our laboratory investigated changes in dialysate DA in the NAc shell and core of rats responding for sucrose pellets and for drugs of abuse. As a follow up to these studies, we recently investigated the changes in NAc shell and core DA transmission associated to oral SA of a 10% ethanol solution. For the purpose of comparison with literature studies utilizing sucrose + ethanol solutions, we also investigated the changes in dialysate DA associated to SA of 20% sucrose and 10% ethanol + 20% sucrose solutions. Rats were trained to acquire oral SA of the solutions under a Fixed Ratio 1 (FR1) schedule of nose-poking. After training, rats were monitored by microdialysis on three consecutive days under response contingent (active), reward omission (extinction trial) and response non-contingent (passive) presentation of ethanol, sucrose or ethanol + sucrose solutions. Active and passive ethanol administration produced a similar increase in dialysate DA in the two NAc subdivisions, while under extinction trial DA increased preferentially in the shell compared to the core. Conversely, under sucrose SA and extinction DA increased exclusively in the shell. These observations provide unequivocal evidence that oral SA of 10% ethanol increases dialysate DA in the NAc, and also suggest that stimuli conditioned to ethanol exposure contribute to the increase of dialysate DA observed in the NAc following ethanol SA. Comparison between the pattern of DA changes detected in the NAc subdivisions under sucrose and ethanol SA likewise suggests that the NAc shell and core DA play different roles in sucrose as compared to ethanol reinforcement
Dopamine responses in the nucleus accumbens shell and core to morphine- and food-conditioned stimuli in morphine sensitized rats
No full textNeurochemical and behavioural responsiveness during sucrose selfadministration
No full textDopamine is implicated in the responsiveness to rewarding properties of natural and
pharmacological stimuli. Conditioned stimuli (CS), linked to rewards such as food or drugs of abuse
(uncontidioned stimuli, US), are essential to support the motivated behaviour. The role of
mesocortical and mesolimbic DA in response to food CS after instrumental paradigm still remains
unclear. The aim of our study was to investigate by microdialysis the impact of instrumental food
CSs and US on behaviour and on basal DA in three terminal DA areas: shell and core of the nucleus
accumbens (NAc) and medial prefrontal cortex (mPFCX), using a food self-administration
paradigm. Rats were trained to acquire sucrose self-administration under a Fixed Ratio 1 (FR 1) or
FR5 variable time out schedule of responding. After training, animals were able to self-administer
sucrose pellets and microdialysis coupled with self-administration experiments were performed.
The main finding of our study was that NAc shell DA has been activated not only by the
conditioned cues but also by food after the instrumental conditioning. When both stimuli are
presented in the same moment the increase of DA is strengthened and prolonged. DA response
has been obtained in NAc core only during US presentation. mPFCX has been activated by each
component of motivated behaviour, except for the response to CS using a FR5 schedule. We can
conclude that DA in the NAc shell plays an important role on the acquisition and expression of
motivated behaviour in food consumption, whereas NAc core and PFCX are less implicated
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