Ethanol abuse produces marked changes in behavior and neurobiological function. Among the behavioral manifestations critical for continued abuse are the profound increases in anxiety-like and reward-seeking behaviors. These outcomes are intimately related and together drive subsequent ethanol abuse. The lateral/basolateral amygdala plays a critical role in the regulation of both anxiety and reward-seeking. Recent work with conditioned behaviors in drug nave animals suggests that segregated but intermingled populations basolateral amygdala principal neurons independently participate within `reward'- and `aversion'-related circuits. Importantly, this segregation is also reflected at the synaptic level with reward or aversion influencing glutamatergic synapses onto these populations in a circuit-specific and mutually exclusive manner. Yet, in spite of this functional segregation in the nave condition, reward-seeking and `aversion' are typically are co- expressed in drug-experienced animals. And, we have shown that dependence-like ethanol exposure robustly alters BLA synaptic function in what appears to be a non-segregated fashion. The juxtaposition of reward-/ affective-circuit control within the BLA, and the effects of chronic ethanol across neurons participating in these circuits, suggests possible cellular mechanisms driving coincidental reward-seeking and negative affect following alcohol dependence. This leads to the CENTRAL HYPOTHESIS of the current application that cooperative synaptic plasticity at distinct BLA inputs controls the interaction between reward-seeking and negative affective states that follow chronic ethanol exposure. To test this hypothesis, we propose three specific aims.
Aim 1 will test the working hypothesis that chronic ethanol, unlike naturally conditioned behaviors, facilitates BLA synaptic function at principal neurons independent of their projection target. We will integrate retrograde tracing and electrophysiological approaches to measure both synaptic function and intrinsic properties of differentially `valenced' BLA neurons participating within distinct `reward' and `aversion' circuits.
Aim 2 will test the working hypothesis that presynaptic facilitation by chronic ethanol is necessary and sufficient for the development of postsynaptic plasticity at distinct synapses. We this `ethanol-induced heterosynaptic cooperation' by integrating optogenetics, chemogentics, and in vitro electrophysiology to 1) assay functional coupling between defined inputs (prelimbic and agranular insular cortex) and 2) disrupt their functional interaction. Finally, for Aim 3, we will test the working hypothesis that ethanol dysregulation of BLA-PrL synapses governs both negative affect and reward seeking following chronic ethanol by integrating chemogenetics with dependence-related ethanol drinking and anxiety-like behavior. The proposed work is both technically innovative and significant because it utilizes state-of-the-art circuit-based approaches to directly define neurobiological mechanisms regulating both ethanol-dependent negative affect and reward- seeking which characterize alcohol abuse and addiction.
The focus of this research project is to understand the impact of chronic ethanol exposure and withdrawal on neurophysiological processes that regulate emotions like anxiety and reward-seeking. Once the project is completed, we will better understand how chronic ethanol exposure and withdrawal alter the brain; and the research could provide specific neurophysiological targets for therapeutics development.
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