Rachel I. Anderson - US grants

Adolescence is a developmental period during which high ethanol use is common. Studies using rodent models of adolescence have observed age-related differences in sensitivity to many of ethanol's properties, including greater sensitivity of adolescents than adults to ethanol-induced social facilitation, but attenuated sensitivity to ethanol- induced motor impairment, sedation, and dysphoria. Such age discrepancies in sensitivity suggest that adolescents and adults may perceive ethanol's subjective effects differently. Ethanol discrimination procedures have been used extensively to gain insight into the interoceptive (i.e., subjective) properties of ethanol, but studies using such procedures have largely neglected adolescent subjects. Using an established animal model of adolescence, the proposed work aims to characterize the ethanol cue in adolescent rats relative to adults using a Pavlovian conditioned approach drug discrimination procedure amenable to testing animals within the relatively short developmental period of adolescence. This procedure will allow for comparison of discrimination acquisition in adolescents and adults under a variety of training conditions that will take into account age differences in ethanol sensitivity. Given that GABA{A} and NMDA receptor systems have been identified as major contributors to the ethanol cue in adult animals, psychopharmacological studies will then examine the role of developmental alterations in GABA{A} and NMDA subunit composition in the ethanol cue in animals of each age by testing subunit-specific compounds in ethanol substitution tests and quantifying subunit expression in specific brain regions across age using both mRNA and protein assays.

DESCRIPTION (provided by applicant): Alcohol dependence is a widespread public health concern with limited treatment options available. This chronic, relapsing disorder is characterized by periods of abstinence followed by a return to heavy use and can be modeled in rodents using a well-established chronic intermittent ethanol (CIE) exposure procedure. While stress is known to promote alcohol consumption and, in particular, trigger relapse, the influence of stress exposure on transition to excessive levels of drinking associated with dependence is less well understood. Our lab has shown that forced swim stress exposure accelerates the rate at which excessive drinking emerges in the CIE model of ethanol dependence and enhances the magnitude of escalated consumption in dependent but not nondependent subjects. The dynorphin/kappa opioid receptor (KOR) system is implicated in modulating both stress responses and ethanol consumption associated with dependence. Thus, it is plausible to suggest that the dynorphin/KOR system may play a role in this stress interaction with the CIE-drinking model. This research project is focused on examining the role of dynorphin/KOR activity in mediating the ability of stress exposure to facilitate and enhance escalation of drinkig in the mouse CIE model of ethanol dependence. The proposed studies will employ both systemic pharmacological and site-specific pharmacosynthetic approaches. For Aim 1, I will use our forced swim stress (FSS)-CIE-drinking paradigm to (1) assess whether administration of the novel, short-acting, selective KOR antagonist FP3FBZ attenuates stress facilitation of CIE-induced escalated drinking and (2) determine whether systemic administration of the KOR agonist U50,488 can substitute for and mimic the effects of FSS exposure in increasing ethanol drinking in CIE- exposed mice compared to nondependent controls. For Aim 2, I will use designer receptor technology (viral injection of Cre-dependent DREADDs) along with prodynorphin-IRES-Cre transgenic mice in the same FSS- CIE-drinking model to (1) determine whether 'silencing' dynorphin neurons (via activation of inhibitory DREADDs) in the central amygdala blocks stress facilitation of CIE-induced escalated drinking and (2) assess whether activation of dynorphin neurons (via excitatory DREADDs) in the central amygdala can substitute for and mimic the effects of stress exposure in enhancing ethanol intake in CIE-exposed mice compared to nondependent controls. Results from this project will advance our understanding of the neural mechanisms underlying the ability of stress to facilitate transition to excessive ethanol drinking associated with dependence, as well as characterize the potential for the KOR system to serve as a therapeutic target for treatment strategies for alcohol dependence.