Chronic escalating cocaine exposure, abstinence/withdrawal, and chronic re-exposure: Effects on striatal dopamine and opioid systems in C57BL/6J mice

► Pdyn mRNA levels were higher in all cocaine groups than in the controls. ► Dopamine was lower in chronic cocaine groups than in acute cocaine and controls. ► Cocaine-induced dopamine increase was higher after re-exposure than exposure group. ► DAT mRNA in CPu were lower in the re-exposure group than in the exposure group.