for nearly a week of drug withdrawal [61]. This is an example where histone acetylation on a gene promoter precedes the induction of gene expression, and suggests that, in addition to marking an actively transcribed gene, histone acetylation may also prime a gene for more rapid or robust transcription in response to a subsequent stimulus without altering its basal level of gene activity. Better knowledge of the genes at which cocaine regulates histone acetylation may result in the identification of novel gene targets and signaling pathways involved in addiction-related behaviors that were previously not appreciated by studies of steady-state mRNA levels.
