Gene expression profiling in dopaminergic brain structures of rats self-administering cocaine. Effect of histone deacetylase inhibition We have shown that injection of the HDAC inhibitor trichostatin A (TsA) to rats is sufficient to decrease their motivation to self-administer cocaine. The aim of the present study was to investigate alterations in gene expression patterns in the Anterior Cingulate Cortex and Nucleus Accumbens of rats self-administering cocaine and treated repeatedly with TsA, and compare them with rats taking only cocaine. We used Affymetrix microarrays to identify genes the expression of which was up-regulated or downregulated during this process. Overall design: Drug self-administration was performed in dark operant chambers under a fixed-ratio 1 schedule of reinforcement that was carried out for 4 days during daily 2 h sessions. Each nosepoke into the active hole triggered the i.v. delivery of a 40 μl cocaine solution (0,3 mg/kg/injection) under the control of the computer. Rats were sacrificed 2 h after the 4th self-administration session; the anterior cingulate cortex and the nucleus accumbens were then dissected. Two treatments comparison