The mechanism and sex-specific effects of nicotinamide on cue-primed cocaine seeking

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Project Summary No FDA approved pharmacological treatments exist for psychostimulant use disorders. Accordingly, development of effective interventions that can countermand the cellular adaptations which drive relapse to drug use remains a priority. Existing evidence indicates that cocaine use leads to elevated markers of oxidative stress, in both humans and preclinical animal models of addiction, and importantly that these markers may contribute to drug seeking behaviors. Nicotinamide (NAM), a form of vitamin B3, component of crucial coenzymes NAD+ and NADP, and poly(ADP-ribose)polymerase (PARP-1) inhibitor can inhibit or reverse markers of oxidative stress. Preliminary data for this application indicate that systemic administration of NAM following cocaine self-administration can specifically reduce reinstatement to cue-primed seeking in male, but not female, rats. The overall goal of this application is to test hypotheses regarding the mechanism behind NAM’s ability to reduce cue-reinstatement in males. Aim 1 will test the hypothesis that NAM’s ability to inhibit PARP-1 contributes to the observed behavioral effect. This will be accomplished with direct delivery of a PARP-1 inhibitor to the central nucleus of the amygdala (CeA) followed by reinstatement testing (Aim 1a) as well as measurement of PARP-1 activity following cocaine self-administration and chronic NAM administration (Aim 1b). The CeA is of particular interest, as direct inhibition of PARP-1 in the CeA has been previously shown to reduce conditioned place preference to cocaine, and the CeA has been implicated specifically in cue- primed reinstatement. Aim 2 will test the hypothesis that NAM reverses cocaine-induced increases in a specific biomarker for oxidative stress in the nucleus accumbens (NAc) and CeA. This will be accomplished through immunohistochemistry and confocal imaging of a cellular marker for oxidative stress following self- administration and extinction. Interestingly, sex differences in the effects of PARP-1 inhibition and NAM treatment have been previously reported, but not in a drug exposure paradigm. Likewise, sex differences in oxidative stress are well known, but have not been examined in drug abuse models. Therefore, the experiments outlined in this proposal will not only inform the utility of NAM as a candidate intervention for responsiveness to drug-paired cues, but will also advance our understanding of the basic cellular responses to cocaine in the brain. I hypothesize that direct inhibition of PARP-1 in the CeA will reduce cue-primed reinstatement, but not cocaine-primed reinstatement, and that NAM administration will reduce cocaine-induced elevated PARP-1 activity in male rats (Aim 1). Further, I hypothesize that NAM administration will reduce cocaine-dependent oxidative stress in the brains of male, but not female rats (Aim 2). Collectively, this proposal will (1) provide training in quantitative fluorescent microscopy, (2) will provide information regarding induction of oxidative stress by cocaine in male and female rats, and (3) will more clearly elucidate the mechanism by which NAM impairs reinstatement of cocaine seeking.