Accumbal shell and core dopamine responsiveness during operant responding for sucrose

BASSAREO, VALENTINA;Musio P;LECCA, DANIELE;DI CHIARA, GAETANO

2010-01-01

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Abstract

Experimental evidence indicates that accumbal dopamine (DA) is critically involved in the reward properties of food and drugs of abuse, that preferentially stimulate DA transmission in the nucleus accumbens (NAc) shell compare to the core. The involvement of the two NAc compartments in the responsiveness to conditioned stimuli (CS), linked with rewards (food, sex, drugs of abuse) (US), is debated. Much discrepancies exist about the impact of food CSs on mesolimbic DA transmission. 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 and prefrontal cortex DA are both affected by food-CS and US. Here we examined the changes of mesolimbic DA in the responsiveness to food CS and US. Using microdialysis technique coupled with self administration paradigm, we have monitored DA transmission in NAc shell and core during: 1) sucrose pellets seeking behavior, 2) presentation of visual and auditory cues associated with primary stimulus and 3) non-contingent administration of sucrose pellets. During our study we found 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. These results provide that DA in the NAc shell plays an important role on the acquisition and expression of motivated behavior in food consumption.