Central amygdala CRF signaling in alcohol dependence:
Where does the CRF come from?
A main goal of the Contet laboratory is to dissect the neural circuitry mediating the well-established role of the neuropeptide CRF (corticotropin-releasing factor) in negative affect. CRF release in the central amygdala (CeA) and subsequent activation of local CRF1 receptors during alcohol withdrawal contribute to negative affect and drinking escalation in dependent animals, but the circuitry underlying these effects is not well understood. Our goal is to identify the source of CRF to the CeA: while CRF1 signaling in the CeA is known to be critical, the cell body location of neurons releasing CRF in the CeA during withdrawal is currently unknown. In addition to investigating CRF pathways, we are also characterizing the downstream link of the circuitry, i.e. CRF1-expressing neurons (collaboration with the Roberto laboratory).
Our approach combines chemogenetic manipulation of specific populations of CRF- and CRF1-expressing neurons, with behavioral analysis, as well as neurotracing and neuronal activity mapping.
Direct molecular targets of ethanol:
What is their relevance to the behavioral effects of ethanol?
Ethanol can alter the activity of multiple proteins. Another goal of the Contet laboratory is to elucidate the in vivo relevance of the action of ethanol on some of these molecular targets, with a focus on G protein-gated inwardly-rectifying potassium (GIRK) channels and large conductance, calcium- and voltage-activated potassium (BK) channels. Despite in vitro evidence that clinically-relevant concentrations of ethanol can bind and activate these channels, whether these actions contribute to the behavioral effects of ethanol remains largely unknown.
We showed that GIRK3 gates activation of the mesolimbic dopaminergic system by ethanol, with direct consequences on binge-like drinking. We are now testing the ability of innovative subtype-specific ligands to selectively reduce excessive alcohol drinking (collaboration with the Slesinger laboratory).
On the other hand, our work on BK channels thus far indicates that the auxiliary subunits β1 and β4 play a critical role in the behavioral adaptations triggered by chronic ethanol exposure, such as tolerance to intoxication and drinking escalation. We are currently testing knockin mice carrying a point mutation in the pore-forming α subunit of BK channels, which renders BK channels insensitive to ethanol without disrupting their physiological activity. Beyond BK channel subunits, we are also studying the effects of ethanol on the network of proteins known to physically interact with BK α. Our approach combines the use of genetically modified mice and virally mediated gene expression manipulation with behavioral analysis, as well as quantitative proteomics (collaboration with the MacCoss laboratory).
Modeling alcohol use disorders in mice
Central to all our projects is a mouse model of alcohol dependence that involves chronic intermittent ethanol vapor inhalation and reliably elicits an escalation of voluntary ethanol drinking in limited-access two-bottle choice sessions. Over the years, the Contet laboratory has made important contributions to the characterization of molecular, cellular and behavioral alterations induced by this procedure. Our overarching goal is to use this model to discover novel vulnerability and resilience factors for excessive alcohol drinking.
At the behavioral level, we seek to enrich the characterization of affective, cognitive and physiological correlates of alcohol drinking escalation in mice. We have already identified affective disturbances that are relevant to the traits associated with alcohol use disorders in humans. A new research direction we are currently developing aims to model in mice the influence of childhood adversity as a risk factor for alcohol dependence, by combining a well-validated model of early life stress with our model of alcohol dependence (collaboration with the Baram laboratory).