A Comparison of the Manipulations of Dopaminergic, Opioidergic or Serotonergic Systems within the Nucleus Acccumbens on the Cue-Evoked Relapse to Food-Seeking
Conditioned stimuli (CSs) associated with reward object availability are known to reinstate reward-seeking behaviors after periods of suppressed responding for a reward. Previous research indicates that the nucleus accumbens (NAcc) is a critical brain region involved in the relapse to drug-seeking behaviors and may likewise be involved in dietary relapse. These three novel experiments utilized a relapse to food-seeking paradigm to test the effects of intra-accumbal pharmacological manipulations on the reinstatement of responding for a food reinforcer by a CS previously associated with the reward. Rats received intra-accumbal infusions of saline or a selective D1 receptor antagonist, mu-opioid receptor agonist, or the neurotransmitter serotonin prior to cue-evoked reinstatement sessions. Both NAcc D1 receptor antagonism by SCH 23390 and mu-opioid receptor agonism by [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) effectively blunted the reinstatement of reward-directed responding by the CS as compared to infusions of the saline vehicle solution. In contrast, the stimulation of serotonin (5-HT) receptors by 5-HT hydrogen maleate did not affect the relapse to food seeking by the reward-associated cues. Together, these data indicate selective roles for specific NAcc receptor activation in the ability for a reward-paired CS to reinstate natural reward-seeking behaviors. Furthermore, these data suggest that the NAcc is likely involved in the failure to abstain from palatable foods in individuals undergoing dietary restriction.
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