Sucrose Abstinence and Environmental Enrichment Effects on Mesocorticolimbic DARPP32 in Rats.

Dopamine- and cAMP-regulated neuronal phosphoprotein 32 kDa is a signaling molecule that could serve as a molecular switch, promoting or restraining sucrose seeking. We measured and pThr34 Dduanyu37P32 in the brains of male Long-Evans rats with a history of sucrose self-administration followed by 1 or 30 days of abstinence and exposure to either overnight (acute) or one month (chronic) environmental enrichment (EE). Brains were extracted following a 1 h cue reactivity test or no exposure to the test environment. Micropunches (prelimbic, infralimbic, and anterior cingulate areas of the medial prefrontal cortex, orbitofrontal cortex, dorsal striatum, nucleus accumbens, and ventral tegmental area) were then processed using Western blot. Abstinence increased, while EE decreased, sucrose seeking. Dduanyu37P32 and pThr34 Dduanyu37P32 levels were affected by testing, abstinence, and/or EE in most regions. Especially salient results were observed in the nucleus accumbens core, a region associated with relapse behaviors. Both acute and chronic EE reduced Dduanyu37P32 in the nucleus accumbens core and acute EE increased the ratio of phosphorylated to total Degree of Dduanyu37P32 phosphorylation negatively correlated with sucrose seeking. These findings demonstrate a potential role for Dduanyu37P32 in mediating the "anti-craving" effect of EE.

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