Sex and Stress Mechanisms of Vulnerability to Addiction

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Sex and stress are known vulnerability factors for addiction, with females and stress-experienced individuals being more sensitive to the reinforcing effects of drugs. Stress also increases recidivism by exacerbating both physiological and psychological symptoms. We hypothesize that sex, stress and cocaine converge within the ventral tegmental area (VTA) having similar, and potentially additive, effects on dopamine (DA) signaling. Ultimately, this leads to altered signal transduction within cortico-limbic-striatal regions. Our preliminary data demonstrate a role for the stress hormone, corticotropin-releasing factor (CRF), in the behavioral, neurochemical and molecular responses to cocaine. We have found that VTA CRF regulates behavioral responses to cocaine; it increases the release of CRF into the VTA and this release sensitizes with repeated cocaine administration. VTA CRF antagonism also blocks cocaine self-administration and cocaine-induced locomotor sensitization. Here we will characterize vulnerability factors associated with addiction using well-established tasks that measure critical processes that contribute to addictive behavior - acquisition, binge, reinstatement - to determine the role for CRF receptor subtypes (CRFR1 or CRFR2)and sex in these effects. Our goal is to establish the mechanism by which VTA CRF contributes to cocaine- induced changes in DA signaling and molecular neuroadaptations within the nucleus accumbens, prefrontal cortex and amygdala using in vivo microdialysis, Western blot analysis of downstream molecular markers (e.g., GluR1, AFosB, CDK5) and proteomics. Aim 1 will determine whether VTA CRF signaling is more sensitive in females compared to males following acquisition of and relapse to cocaine self-administration. We will examine how sensitivity is related to estrus cycle and determine the role of estrogen and progesterone on cocaine-induced VTA CRF responses. Both cue- and stress-induced relapse will be investigated. We will also use a transgenic line of mice in which gonadal sex and chromosomal sex are independent to test the hypothesis that components of addiction are differentially mediated by sex chromosomes and gonadal hormones. Our preliminary data show independent contributions of chromosomal sex and gonadal sex in habit formation and cocaine-induced locomotor sensitization. Aim 2 will examine whether prior stress experience sensitizes cocaine-induced CRF responses and intracellular signaling in the VTA to test the hypothesis that these effects are more pronounced in females. Aim 3 will use CRF receptor deficient mice to establish whether CRF receptors are necessary for cocaine self-administration. Acquisition of and relapse to cocaine self-administration (cue and stress) and VTA CRF responses in males and females will be assessed after prior chronic stress. Together our studies will clarify the relationship and potential converging effects of sex and stress on VTA functioning in vulnerability to addiction.