Project Summary/Abstract Despite years of research there are still no approved pharmacotherapies for treatment of cocaine use disorder. Recently, there has been an alarming surge in cocaine-associated emergency room admissions and overdose deaths. In addition to acute adverse health effects, protracted use of cocaine results in maladaptive neuroadaptations that produce an enduring vulnerability to relapse even after extended abstinence. Consequently there remains a critical need to identify effective treatments for cocaine relapse prevention that may normalize some of these neuroadaptations. The primary objective of this research is to determine if the FDA-approved diabetes drug metformin can be repurposed for the treatment of cocaine relapse based on published data linking one of its protein targets, adenosine monophosphate activated protein kinase (AMPK), to cocaine responses. The central hypothesis is that metformin reduces cocaine seeking through activation of AMPK. Aim 1 is designed to determine if metformin is able to reduce cue-induced reinstatement, the rodent correlate of relapse, and if this depends on AMPK activation. We will determine if intracranial administration of metformin within the nucleus accumbens core (NAcore), a brain region known to regulate cue-induced relapse, is sufficient to reduce cue-induced reinstatement in rats trained to self-administer cocaine. More importantly, we will establish whether systemic administration of metformin is effective at reducing reinstatement. Intracranial metformin will be delivered acutely prior to a reinstatement test, and systemic metformin will be given chronically during abstinence with extinction training. Pharmacologic or genetic inhibitors of AMPK will be used to probe metformin's dependence on this kinase. While phosphorylated (active) AMPK is reduced following cocaine self-administration and extinction, phospho-AMPK is increased by acute cocaine or following a cue-induced reinstatement test. Aim 2 will test whether the cocaine-related induction of AMPK activity is a compensatory response to limit reward. We hypothesize that the observed increase in the activated pAMPK in NAcore associated with cue-induced reinstatement is related to extinction rather than drug seeking. Memory manipulations will be used to distinguish cue extinction from cue reactivation and pAMPK will be measured in NAcore. Lastly, we will assess whether metformin pretreatment designed to pre-activate AMPK is capable of inhibiting the acquisition of cocaine self-administration revealing potential prophylactic effects. These results have the potential to guide development of novel therapeutic interventions for cocaine use disorder and broaden the scope of our understanding of the molecular mechanisms underlying vulnerability to cocaine relapse.