Withdrawal stress following chronic ethanol exposure results in heightened anxiety-like behaviors that contribute to relapse in abstinent alcoholics. However, very little is known about the neurobiological mechanisms controlling these outcomes. Animal models can make significant contributions towards understanding these issues. For example, we have shown that the rat glutamatergic and GABAergic synaptic function in the lateral/basolateral amygdala (BLA) are dramatically regulated by chronic ethanol exposure and withdrawal. Similarly, the rat BLA CRF/urocortin system appears to enhance excitatory BLA responses. Chronic ethanol-related alterations in glutamate, GABA, and CRF/urocortin all potentially contribute to withdrawal-anxiety. But, the precise contributions of any individual alteration are confounded by their fundamental contributions in ethanol-naive animals. The C57BL/6J (B6) and DBA/2J (D2) mouse offer an alternative approach. These inbred lines differ dramatically with respect to a number of different ethanol related behaviors, including their behavioral sensitivity to chronic ethanol exposure and withdrawal. This is extended to withdrawal-anxiety by preliminary evidence provided in the current application that shows greater D2 sensitivity. Furthermore, our published and preliminary findings suggest that BLA GABAergic and potentially glutamatergic synaptic function in these two mouse lines are markedly distinct. This strongly suggests that chronic ethanol exposures producing substantial withdrawal-anxiety in one strain but not the other can be used to highlight individual neurophysiological changes with the greatest behavioral impact. The proposed experiments will therefore test the central hypothesis that the greater withdrawal-related increases in anxiety in D2 mice will be reflected by more significant increases in BLA excitatory neurotransmitter systems, like glutamate and CRF/urocortin. Our primarily electrophysiological analysis of these systems as well as GABAergic function will be integrated with both behavioral measures of anxiety during withdrawal-stress in B6, D2, and genetically modified mice. The proposed experiments are significant because they offer a unique opportunity to define specific BLA neurobiological targets for future therapies.
The proposed research will help establish the neural systems important for abnormal behaviors caused by chronic ethanol exposure. The application uses rodent models, specifically inbred mouse strains, behavioral measures of anxiety, and a number of characterizations in brain tissue to accomplish this overall goal.
|McCool, Brian A; Chappell, Ann M (2014) Persistent enhancement of ethanol drinking following a monosodium glutamate-substitution procedure in C57BL6/J and DBA/2J mice. Alcohol 48:55-61|
|McCool, Brian A; Christian, Daniel T; Fetzer, Jonathan A et al. (2014) Lateral/basolateral amygdala serotonin type-2 receptors modulate operant self-administration of a sweetened ethanol solution via inhibition of principal neuron activity. Front Integr Neurosci 8:5|
|Christian, Daniel T; Alexander, Nancy J; Diaz, Marvin R et al. (2013) Thalamic glutamatergic afferents into the rat basolateral amygdala exhibit increased presynaptic glutamate function following withdrawal from chronic intermittent ethanol. Neuropharmacology 65:134-42|