Epigenetics and Escalated Response to Cocaine

In the nucleus accumbens (NAc) and caudate-putamen (CPu), drugs of abuse like cocaine induce Fosb, an immediate response gene that codes for the transcription factor ΔFosB; Fosb expression returns to baseline after about a month. These researchers examined the mechanisms of Fosb expression induced by cocaine administration in cocaine-naive rats and in those that had received cocaine for 10 days followed by 28 days of abstinence.

Administration of cocaine induced more locomotion in cocaine-experienced abstinent animals than in drug-naive animals. In the NAc but not the CPu, this behavioral sensitization was accompanied by greater expression of Fosb mRNA and higher levels of the ΔFosB protein. Greater susceptibility of Fosb to induction in coc…