Stress is a well-known factor in promoting heavy drinking and relapse to drinking in alcoholics, and avoidance of the negative affective symptoms of ethanol withdrawal (e.g. anxiety) is also believed to play a critical role in relapse to heavy ethanol use. Further, anxiety disorders may predispose individuals to drink heavily and these high intakes may exacerbate the interaction of heavy drinking and anxiety. Negative affective behaviors are modulated by neuropeptides such as dynorphin, and its target, kappa opioid receptors (KORs). We will use a mouse model of chronic intermittent ethanol (CIE) exposure combined with forced swim stress to understand the role that KORs play in the maladaptive neurobiological changes induced by stress/ethanol interactions. Our previous work revealed that the function of the dynorphin/KOR system in the nucleus accumbens (NAc) was robustly up-regulated by chronic ethanol exposure and withdrawal in a time/exposure dependent manner in both the CIE model in mice and in a long-term voluntary ethanol drinking model in monkeys. In addition, in mice we found that systemic administration of a KOR antagonist reduced anxiety/compulsive behaviors (marble burying) and withdrawal-induced excessive drinking. Because norepinephrine (NE) and dopamine (DA) are both involved in negative affective responses to stress, and are known targets of KOR activity, we will examine KOR regulation of DA signaling in the NAc, which regulates motivation to drink alcohol, and NE signaling in the basolateral amygdala (BLA), which regulates stress/anxiety-related behaviors. We have established that KOR inhibition of DA signaling in the NAc is up- regulated by chronic intermittent ethanol (CIE) exposure, and we will expand these findings to include activation of the NE system by forced swim stress (FSS) and CIE, regulation of this system by KORs, and interactions with DA that may exacerbate negative affective responses and subsequent ethanol drinking. The overall goal is to define FSS and CIE-induced adaptations in stress-responsive limbic circuitry nodes that are responsible for withdrawal-associated negative affect and that can be targeted for the treatment of alcoholism.
Stress and anxiety contribute to heavy alcohol drinking and alcoholism, although the neurobiological basis of this interaction is not well understood. The proposed studies will examine the involvement of the endogenous opioid dynorphin and its target, the kappa opioid receptor, in mediating anxiety-like behavior and increased alcohol drinking in mice that are exposed to repeated stress over several weeks. The results of these studies will help define the role of dynorphin and kappa opioid receptors in stress-induced relapse to alcohol drinking and lead the way toward developing targeted pharmacological therapies to reduce the impact of stress in alcoholics.
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