Figure 4. Striatal ELK1 protein levels correlate with heroin use.

(A) A strong positive correlation (r²=0.70) was observed between ELK1 protein expression in the putamen and urine levels of the rapid heroin metabolite 6-MAM in human heroin abusers; seven subjects had detectable 6-MAM levels. (B) ELK1 mRNA levels negatively correlate with the age of onset of heroin use in human subjects that carry the G allele of rs2075572 (r²=0.37), with the strongest correlation in G/G subjects (r²=0.95). (C) Total ELK1 protein levels in the dorsal striatum are positively correlated (r²=0.79) to history of heroin intake in a rat heroin self-administration model 1 hour after the last drug session, while a negative correlation (r²=0.72) was observed 24 hours later (D). N= 5–11/group.