Given the challenge of human postmortem studies that lack a complete drug history about the subjects, we examined the regulation of ELK1 in a rat model of addiction using a heroin self-administration paradigm where animals controlled their individual drug intake.(26–28) Since the post-mortem interval for many of the human heroin subjects is relatively short, we examined ELK1 protein 1 hour after the last self-administration session as well as 24 hours later to obtain insights regarding the stability of the observations. ELK1 expression was tightly correlated with each animal’s history of heroin intake. We observed a positive correlation 1 hour after the final heroin self-administration session (r2=0.79, p<0.05; Fig 4C) that was reversed 24 hours later with a negative correlation to ELK1 levels (r2=0.72, p<0.001; Fig 4D).
