Modifications in DARPP‐32 phosphorylation pattern after repeated palatable food consumption undergo rapid habituation in the nucleus accumbens shell of non‐food‐deprived rats

In non‐food‐deprived rats a palatable meal induces a transient increase in dopamine output in the prefrontal cortex and nucleus accumbens shell and core; habituation to this response develops with a second palatable meal, selectively in the shell, unless animals are food‐deprived. A palatable meal also induces time‐dependent modifications in the dopamine and cAMP‐regulated phosphoprotein of Mr 32 000 (DARPP‐32) phosphorylation pattern that are prevented when SCH 23390, a selective dopamine D₁ receptor antagonist, is administered shortly after the meal. This study investigated whether dopaminergic habituation in the shell had a counterpart in DARPP‐32 phosphorylation changes. In non‐food‐deprived rats, two consecutive palatable meals were followed by similar sequences of modifications in DARPP‐32 phosphorylation levels in the prefrontal cortex and nucleus accumbens core, while changes after the second meal were blunted in the shell. In food‐deprived rats two consecutive meals also induced similar phosphorylation changes in the shell. Finally, SCH 23390 administered shortly after the first palatable meal in non‐food‐deprived rats inhibited DARPP‐32 phosphorylation changes in response to the first meal, and prevented the habituation to a second meal in terms of dopaminergic response and DARPP‐32 phosphorylation changes. Thus, dopamine D₁ receptor stimulation plays a role in the development of habituation.