Exploring a role for mPFC CRF circuitry in promoting stress-enhanced alcohol consumption

PROJECT SUMMARY Alcohol use disorder (AUD) is the fourth leading cause of preventable death in the United Sates and according to the Centers for Disease Control and Prevention alcohol is responsible for over 178,000 deaths in the last year. Chronic stress can be a key factor that leads to increased alcohol consumption, and thus increases risk for the development of AUD. The medial prefrontal cortex (mPFC) is a key brain region involved in decision making and impulsivity and becomes dysregulated following both chronic alcohol and chronic stress. Corticotropin releasing factor (CRF) is a pro-stress neuropeptide that is primarily released from the hypothalamus in response to stress, however, the role of CRF in extra-hypothalamic brain regions, primarily the mPFC, is widely understudied. CRF has multiple binding partners, the most prominent in the mPFC being CRF receptor 1 (CRFR1). While both CRF+ and CRFR1+ neurons are prevalent in the mPFC, their function in regulating voluntary alcohol consumption following chronic alcohol and stress is unknown. Preliminary electrophysiology data from the lab shows that chronic alcohol and stress increase intrinsic excitability of cortical CRF+ neurons, while others report that one of the putative downstream targets of cortical CRF+ interneurons, CRFR1+ neurons, have weakened excitability following chronic alcohol and withdrawal. To date, no one has examined the effects of the combination of chronic alcohol and stress on these discrete neural populations in the mPFC. The overall hypothesis of this proposal is that the CRF system in the mPFC is altered after chronic alcohol and stress, which drives escalated alcohol consumption. Specifically, CRF+ and CRFR1+ neurons in the prelimbic cortex are differentially engaged during voluntary alcohol consumption and have opposing mediation of stress-induced alcohol drinking. To examine this, this proposal will use a model of chronic alcohol and stress and measure the cellular activity of cortical CRF+ and CRFR1+ neurons during alcohol drinking, as well as manipulate these cells using chemogenetics to demonstrate their functional role in mediating these effects. Specifically, in Aim 1 we will use fiber photometry to record in vivo calcium dynamics of CRF+ GABAergic interneurons by expressing a Cre-dependent calcium biosensor (GCaMP) in Crh-ires-Cre mice. Aim 2 will use Crhr1-ires-Cre mice to examine cortical CRFR1+ projection neuron calcium dynamics using a Cre-dependent GCaMP and fiber photometry while simultaneously inhibiting CRF+ cortical neurons using a Crh-promoter expressing viral vector to drive expression of an inhibitory DREADD (designer receptors exclusively activated by designer drugs) in CRF+ neurons in the same mice. The results from these experiments will be the first to examine the activity and function of these neurons in the context of chronic alcohol and stress and will provide a foundation allowing us to further understand the impact of cortical dysregulation following chronic alcohol and stress.