The development and progression of alcohol use disorders is thought to involve adaptive changes in neural circuits that underlie negative affective states, like anxiety. One hypothesis that is garnering increasing support is that these adaptive changes gradually shift motivation for alcohol away from positive reinforcement (e.g. euphoria) toward negative reinforcement (e.g. relief from negative affective states). Although much is known about the neural underpinning of alcohol's positive reinforcing effects, the neural substrates linking negative reinforcement and alcoholism remain less clearly defined. The lateral/basolateral amygdala (BLA) plays a major role in anxiety-like behaviors and alcohol drinking and there is growing evidence that dysregulation of this brain region contributes to the pathophysiology of both anxiety disorders and addiction. Surprisingly, much remains unknown about the intrinsic circuitry of this brain region or the neuromodulatory systems that influence BLA synaptic transmission. During the last funding period, we discovered that beta3-adrenoceptor activation enhances a novel GABA circuit in the BLA and that this effect can decrease anxiety-like behaviors and ethanol seeking behaviors. We have also recently identified powerful effects of the neuromodulator adenosine on BLA synaptic transmission. In other studies, we demonstrated that a rodent early life stress model engenders several behavioral and neurobiological alterations that have also been associated with increased vulnerability to alcoholism. The first two aims of this proposal will determine the neurobiological effects of adenosine A1 and A2a receptor activation on excitatory and inhibitory neurotransmission in the rat basolateral amygdala (BLA) and whether intra-BLA activation of these receptors reduces measures of anxiety-like behavior.
Aims 3 and 4 will employ the early life stress model to identify enduring perturbations in norepinephrine and adenosine modulation of BLA synaptic transmission that may contribute to increased vulnerability (and resilience) to excessive alcohol drinking behaviors. Other experiments will determine if pharmacological manipulations that restore normal BLA function can reduce the increases in anxiety-like behavior and ethanol drinking that result from early life stress.
The proposed studies are designed to identify novel neurobiological mechanisms linking early life stress and increased vulnerability to alcohol use disorders. These studies may also lead to the discovery of more effective pharmacotherapies for the treatment of alcoholism, particularly in individuals where anxiety and negative reinforcement play a major role in the disease.
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