Changes in nucleus accumbens core translatome accompanying incubation of cocaine craving

In the ‘incubation of cocaine craving’ model of relapse, rats self-administer cocaine and then experience a prolonged abstinence period. After this prolonged abstinence period, rats exhibit a progressive intensification (incubation) of cue-induced craving, and the expression of incubated craving depends on plasticity of excitatory synaptic transmission in nucleus accumbens (NAc) core medium spiny neurons (MSN). Previously, we found that the maintenance of this plasticity depends on ongoing protein translation, and that regulation of translation is altered after incubation of cocaine craving. Here we used male and female rats that express Cre recombinase in either dopamine D1 receptor- or adenosine 2a (A2a) receptor-expressing MSN to express a GFP-tagged ribosomal protein in a cell-type specific manner, enabling us to use Translating Ribosome Affinity Purification (TRAP) to isolate actively translating mRNAs from both MSN subtypes for analysis by RNA-Seq. We compared rats that self-administered saline or cocaine. Saline rats were assessed on abstinence day (AD) 1, while cocaine rats were assessed on AD1 or AD40-50. For both D1 and A2a MSN, there were few differentially translated (DT) genes between saline and cocaine AD1 groups. In contrast, a pronounced divergence was observed between cocaine rats on AD1 and AD40, and this was far more robust in D1 MSN. Finally, all comparisons revealed sex differences in translating mRNAs. This study, the first to combine TRAP-seq, transgenic rats, and a cocaine self-administration paradigm, identifies translating mRNAs specifically linked to incubation of cocaine craving in D1 and A2a MSN of the NAc core. Nucleus accumbens punches from adult male and female D1:Cre and A2a:Cre rats that self-administered cocaine or saline and were euthanized 1 or 40 days later. Translating RNA affinity purification (TRAP) was run on the tissue to collect TRAP RNA selectively from D1 or A2a (D2) expressing medium spiny neurons.