Catherine Marcinkiewcz - US grants

DESCRIPTION (provided by applicant): Alcohol abuse is a significant public health burden that is often difficult to manage with current treatment options (NIAAA 1994). Chronic ethanol can induce adaptations in neural circuits that govern emotional behavior and anxiety and may have relevance for ethanol dependence. Serotonin 2c (5HT2c) and corticotrophin-releasing factor (CRF) systems are both dysregulated by chronic ethanol and contribute to the anxiety-inducing effects of ethanol withdrawal (Koob 2001; Overstreet 2003; Knapp 2004; Overstreet 2006; Heilig 2007). The goal of this application is to unravel the molecular basis for 5HT-CRF interactions in the bed nucleus of stria terminalis (BNST), a brain region that was previously shown to be an important neural substrate of anxiety and relapse (Erb 1999). Our central hypothesis is that chronic intermittent ethanol (CIE) increases 5HT2c receptor (5HT2c-R) signaling in the BNST, which in turn activates CRF neurons, causing an increase in anxiety-like behavior that is observed during ethanol withdrawal. Specific Aim 1 is designed to investigate the impact of 5HT2c-R signaling on excitability of CRF neurons in the BNST using ex vivo slice electrophysiology in a recently developed CRF-Ai3 reporter mouse. [Given the potential confounds associated with CRF reporter mice, we include a converging approach that targets the dense CRF projection from the BNST to VTA. Using retrograde tracer beads injected into the VTA of wild-type mice, we will record from putative CRF neurons in the BNST that project to the VTA.] The effects of 5HT2c-R agonists and antagonists on membrane potential and current induced spiking will be examined to determine if 5HT2c-R activation depolarizes CRF neurons in the BNST using both approaches. We will also investigate downstream signaling pathways (e.g. Gq/11/PLC) that may underlie 5HT2c-R effects in CRF neurons. Together, these experiments will clarify the functional interactions between 5HT and CRF systems in the BNST. Specific Aim 2 examines the effects of CIE on 5HT2c-R signaling in the BNST. Using ex vivo slice electrophysiology in CRF-Ai3 reporter [and VTA tracer-injected wild-type mice], we will examine the effects of CIE on excitability and 5HT2c signaling in CRF neurons. Together, these experiments will provide converging results indicating whether CIE leads to functional adaptations in 5HT2c-R systems in the BNST. Specific Aim 3 is designed to clarify the role of 5HT2c-R signaling in the BNST in anxiety-like behavior following CIE. Preliminary data indicates that CIE induces anxiety-like behavior in mice in the social approach test. Given the putative actions of 5HT2c-Rs on CRF neurons in the BNST, we predict that 5HT2c-R antagonists infused into the BNST will alleviate anxiety associated with ethanol withdrawal. The results of this study will indicate whether 5HT2c-R systems in the BNST are a potential target for the treatment of anxiety during ethanol withdrawal. In total, the proposed research will provide essential information concerning 5HT2c- CRF interactions in the BNST and the role that these systems play in alcohol-induced anxiety.

? DESCRIPTION (provided by applicant): Alcohol abuse is a significant public health burden that is often difficult to manage with current treatment options. Chronic intermittent ethanol (CIE can induce adaptations in neural circuits that govern anxiety and motivated behavior and may have relevance for ethanol dependence. The goal of this application is to dissect neural circuits that are critically involved in dependence induced escalations in ethanol drinking. Recent evidence indicates that both 5-HT2CR and kappa opioid receptor (KOR) in the nucleus accumbens (NAc) shell contribute to CIE enhanced drinking. My central hypothesis is that chronic intermittent ethanol (CIE) augments 5-HT release in the NAc, which activate local dynorphin neurons that in turn reduce dopamine release. This degrades the reward value of ethanol and leads to increased ethanol consumption. In Specific Aim 1, I will use a multiplexed DREADD strategy to delineate the role of 5HT inputs to the NAc shell in CIE induced elevations in voluntary ethanol drinking. In Specific Aim 2, I will examine the impact of CIE on excitability f dynorphin neurons using slice electrophysiology. Based on preliminary data that stimulation of NAc dynorphin neurons modulates dopamine release in the NAc, I will also use slice voltammetry to examine how CIE shapes dynorphin-dopamine interactions in the NAc. Specific Aim 3 is designed to clarify the role of these NAc dynorphin neurons in excessive ethanol drinking after CIE. In total, the proposed research will provide essential information concerning the actions of CIE on the 5-HT-dynorphin circuits in the NAc that specifically drive excessive alcohol consumption.

Project Summary / Abstract Alcohol use disorders (AUDs) are associated with neurodegeneration and cognitive dysfunction, but the impact of alcohol use on Alzheimer's disease and related dementias (ADRD) is unknown. Our work suggests that chronic alcohol can alter the activity of serotonin (5-HT) neurons in the DRN, which may cause disruption in sleep homeostasis in the early stages of ADRD. Both AUD and ADRD are associated with chronic insomnia, but to date no studies have linked alcohol-induced sleep disturbances to tau-based neuropathology in the brain. Sleep disruption also induces microglial activation and aging, which can promote the spread of tau pathology in the brain. In Aim 1, we will use EEG, fiber photometry, electrophysiology and DREADD-based manipulations of neural activity in vivo in mice expressing human tau pathology (htau mice) to determine whether chronic alcohol exacerbates sleep deficits and whether enhanced neural activity in 5-HT neurons contributes to sleep disruptions. In Aim 2, we will examine the effect of chronic alcohol on microglia and their contribution to the progression of tau pathology in the DRN. In Aim 3, we will determine whether chronic alcohol can facilitate the spread of tau pathology from the DRN to other brain regions using an AAV-based strategy for expressing tau pathology exclusively in 5-HT neurons. 3D immunolabeling and light sheet imaging using the iDISCO technique will be used to identify areas and quantify the extent of tau spread. We will also examine whether neural activity in 5-HT neurons and microglial activation contributes to this spread. In total, the proposed research will provide mechanistic insight into the impact of chronic alcohol on early accumulation and spread of tau pathology in the brain and the later development of cognitive and memory deficits.

Project Summary / Abstract Alzheimer's disease (AD) is a devastating age-related neurodegenerative disease that can severely curtail life quality and expectancy. Depression and sleep disorders manifest decades before disease onset and may serve as an important early biomarker. Serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) exhibit neurofibrillary changes in the early stages of AD, which may contribute to some of these early non-cognitive symptoms. The goal of this application is to determine whether tau accumulation in 5-HT DRN neurons induces depressive-like behaviors and disordered sleep, leading to chronic sleep disruption. These sleep deficits, in turn, may promote hyperexcitability of 5-HT neurons and lead to neurodegeneration. The increased activity in 5-HT neurons due to sleep deprivation also facilitates the spread of tau pathology to the entorhinal cortex (EC), another region that is impacted early in the course of AD. Loss of 5-HT inputs from the DRN to the EC will disinhibit neurons that project to the hippocampus, precipitating tau spread and the onset of cognitive and memory problems. In Aim 1, we will use in vivo fiber photometry to measure neural activity in 5-HT neurons during tests of depressive-like behavior in mouse models of tauopathy to see if the normal function of these neurons is negatively impacted. We will also monitor 5-HT activity during sleep to see if that is altered by tau pathology. In Aim 2, we will examine the effect of sleep deprivation on 5-HT neuronal excitability and the progression of tau pathology in the brain using electrophysiology and 3D imaging. The role of increased neural activity in 5-HT neurons on the spread of tau pathology will also be examined using chemogenetic manipulations of neural activity. In Aim 3, we will determine whether tau-induced loss of 5-HT inputs to the EC alters 5-HT signaling in principal neurons that project to the hippocampus. We will also establish a role for 5-HT/5-HT2A receptor signaling in the spread of tau pathology to the hippocampus and the onset of cognitive deficits. In total, the proposed research will provide essential information concerning the impact of tau pathology on early behavioral symptoms of AD and the later development of cognitive and memory deficits.