Mesolimbic dopamine responsiveness to food conditioned stimuli after instrumental conditioning paradigm

BASSAREO, VALENTINA;Musio P;LECCA, DANIELE;Di Chiara G.

2009-01-01

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Abstract

Dopamine (DA) is regarded to play an important role in the reward properties of natural and pharmacological primary stimuli. It is well known that conditioned stimuli (CS), linked with rewards (food, sex, drugs of abuse) (US), are essential to support a motivated behavior. Much discrepancies exist about the impact of food CSs on mesolimbic DA transmission. In particular it has been reported that after classical conditioning paradigm, nucleus accumbens (NAc) shell DA shows responsiveness to food US, but it is unresponsive to food CS, while NAc core and prefrontal cortex (PFCX) DA are both affected by food-CS and US. The aim of our study was to clarify the role of mesolimbic DA in the responsiveness to CS and to US. Using microdialysis technique coupled with self administration paradigm, we have studied DA transmission in NAc shell and core 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.