Yuval Silberman, Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): Although alcohol (EtOH) is one of the oldest known drugs of abuse, the neuroliogical mechanisms underlying EtOH's actions are not fully known and as such, it remains difficult to understand how one may lose control of normal EtOH drinking resulting in alcoholism. Alcoholism is often found to be comorbid with anxiety and stress disorders, and while the eitology of this comorbidity is not fully known it has been proposed that since EtOH has long been known as an anxiolytic agent, some may imbibe as a way to selfmedicate their anxious or stressed states. Withdrawal from high EtOH levels has also been shown to result in an enhancement of anxious/stressed states, which may result in continued EtOH use and abuse. Therefore, it is hypothesized that EtOH may predominantly effect areas of the central nervous system (CMS) which mediate stress responses and anxiety, such as the basolateral amygdala (BLA). GABAergic synapses in the BLA have been shown to play a major role in emotional responses such as anxiety. Extensive research has shown that at least part of EtOH's effects in the CMS are due to an increase in GABAergic neurotransmission in numerous brain regions through both pre- and post-synaptic sites. Norepinephrine (NE), which is intimately linked to stress and anxiety disorders, has been shown increase GABA release in the BLA. Our preliminary data shows that NE receptor antagonists can block the potentiating effect of EtOH at a subset of GABAergic interneurons. Therefore it is hypothesized that EtOH enhances GABAergic transmission in the BLA in part via NE-receptor activity. The first specific aim is to determine the mechanisms by which acute EtOH enhances GABAergic neurotransmission at two subset of interneurons in the BLA. This aim will rely on whole-cell patch clamp electrophysiological methods to determine if the effects of bath application of EtOH on slices of BLA tissue are pre- and/or post-synaptic utilizing a combination of protocols focusing mainly on evoked inhibitory postsynaptic currents (IPSCs) spontaneous and miniature IPSCs and paired-pulses facilitation studies to isolate pre- and post-synaptic components of the EtOH enhancement of GABAergic neurotransmission. The second specific aim will determine the mechanism by which NE interacts with EtOH at BLA GABAergic synapse and which NE-receptor subtype mediates this effect. We will be using similar methods as described above as well as combinations of NE receptor agonists and antagonists to isolate the mechanism of the proposed NE-EtOH interaction in this brain region. The third specific aim will focus on the effects of chonic intermittent EtOH exposure via inhalation chamber exposure on subsequent acute EtOH exposure and the NE-EtOH interaction studied aims 1 and 2. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Alcohol use disorder (AUD) is a chronic relapsing disease that has a great impact on individual health as well as the socio-economic well-being of the US as an estimated $184 billion dollars are spent annually on AUD related problems. Therefore, finding pharmacotherapeutic targets to alleviate AUDs is of great importance. Recent research shows that the initial motivation to excessively consume alcohol may be reliant upon activation of the brain's positive reinforcement system which is predominantly mediated by dopamine (DA) release from the ventral tegmental area. At some point in the development of AUDs a transition is thought to occur such that motivation to excessively consume alcohol switches from reliance on positive reinforcement to negative reinforcement systems. The extended amygdala, a brain region important in mediating anxiety and stress responses, and corticotrophin releasing factor (CRF), a neurotransmitter thought to be involved in stress reactivity, are thought to be heavily involved in the negative reinforcement pathways required for AUD development. However, the exact nature and neurocircuitry involved in the switch between utilizing positive and negative reinforcement systems during the development of AUDs is not yet known. Recent work from our lab has shown a potentially direct connection between positive and negative reinforcement systems whereby DA can elevate CRF levels in the bed nucleus of the stria terminalis (BNST), a component of the extended amygdala that is often described as a middle manager of information in both the positive and negative reinforcement pathways. Alcohol exposure has long been shown to increase DA levels in many brain regions, including the BNST, which suggests that alcohol exposure would also increase BNST CRF levels. CRF has been shown to increase the excitability of BNST neurons, which has further been shown to increase anxiety-like behaviors in many rodent models. In addition, withdrawal from alcohol exposure has also been shown to increase CRF levels in the BNST and increase anxiety. Furthermore, repeated CRF receptor stimulation has been shown to cause a sensitization of anxiety-like behaviors regulated by the BNST. Therefore, repeated alcohol exposures and withdrawals would be expected to cause increased levels of CRF in the BNST, both via indirect modulation via DA during alcohol exposure and by directly increasing CRF release during withdrawal. This interaction between alcohol DA and CRF is hypothesized to cause a sensitization of BNST CRF receptors and therefore be the initial transition point between positive and negative reinforcement in AUD development. This proposal will integrate electrophysiological, pharmacological, behavioral, and fluorescent imaging techniques to determine if BNST CRF sensitize following chronic intermittent alcohol exposure and which BNST output neurons are affected by this sensitization. Successful completion of these studies may reveal new insights into AUD development and possibly uncover novel targets for future pharmacological interventions in the treatment of this debilitating disease. PUBLIC HEALTH RELEVANCE: Alcoholism is a devastating and costly disease hypothesized to develop due a transition in the neurocircuitry responsible for initial excessive alcohol drinking and latter dependency. One potential transitional component may be a unique pathway in the bed nucleus of the stria terminalis, a brain region involved in the regulation of the separate reward and stress systems, which may be especially sensitive to insults by chronic alcohol exposures and withdrawals. This proposal aims to examine this unique pathway and determine how it may change following repeated alcohol exposures and withdrawals with the goal of revealing novel targets for the development of new and better treatments for alcoholism.

DESCRIPTION (provided by applicant): Alcoholism is a vexing health problem accounting for 2.5 million deaths per year around the world, representing the third largest risk factor for global disease. Alcoholism is the number one leading risk factor for disease in the United States, as an estimated 43% of men and 28% of women can be classified as binge drinkers and about 7% of Americans are considered alcoholics. One of the major issues facing the treatment of alcoholism is the high rate (50-90%) of relapse. Finding new strategies for the treatment of alcoholism is my major long-term career goal. Long-term stress vulnerability and reduced capacity to control drinking are hallmarks of alcoholism and determining the causes of these symptoms may lead to better treatments strategies. These enduring dysfunctions likely result from equally enduring changes in key neuronal pathways involved in stress and reward signaling, such as the bed nucleus of the stria terminalis (BNST). Corticotropin releasing factor (CRF) signaling within the BNST plays a key role in negative reinforcement-based enhancement of alcohol drinking induced by chronic alcohol exposure. This system may also play an important role in the inability of alcoholics to limit drinking and in their propensity for relapse However, the mechanism by which chronic alcohol recruits this important pathway at the intersection of stress and reward signaling remains unclear. Determining the mechanisms by which chronic alcohol exposure alters BNST signaling in my current short-term goal. In this proposal we will use a combination of cutting edge neuroscience techniques to determine how BNST-CRF neurocircuitry is integrated with alcohol sensitive brain regions in the naive state and examine how chronic alcohol exposures disrupts this connectivity. Accumulating evidence suggests that increased norepinephrine transmission in the BNST may play a critical role in the enhancement of BNST-CRF signaling during alcohol withdrawal. Our previous findings indicate that alpha- adrenergic receptors activation generally decreases BNST excitability while beta-adrenergic receptors activation can depolarize BNST-CRF neurons and promote increased BNST excitability. Therefore, alpha- and beta-adrenergic receptors may balance the overall effect of norepinephrine on BNST activity. In a related brain region, the basolateral amygdala, alpha/beta-adrenergic receptors also balance norepinephrine modulation of neuronal activity and stress can shift this balance towards increased beta-adrenergic receptor excitation. Since chronic alcohol exposure is a stress, chronic alcohol may shift the alpha/beta -adrenergic balance to promote norepinephrine mediated excitation of BNST-CRF neurons during withdrawal. We will explore this hypothesis in Aim 1 of this proposal in a novel transgenic CRF reporter mouse using a combination of optogenetic, electrophysiological, and pharmacologic approaches. Dendritic spines play a key role in the regulation of afferent-specific plasticity and chronic drug exposure can alter dendritic spine morphology. However little is known about how chronic alcohol may alter BNST-CRF neuron dendritic spines. We propose that chronic alcohol may induce long-term adaptations in the dendritic architecture of BNST-CRF neurons that may lock in enduring BNST-CRF neuron excitability. This hypothesis will be examined in Aim 2 using a novel combination of electrophysiological and neuroanatomical approaches. These two aims will involve the development of new scientific skills marrying the selective examination of regulatory influences onto BNST-CRF neurons with studies examining the form and function of this neuronal population critical to the development of alcoholism. This work will be mentored by leaders in the fields of alcoholism (Dr. Danny Winder) and neuroanatomy (Dr. Ariel Deutch) at Vanderbilt University School of Medicine, a world-renowned biomedical research institution. While these two aims will allow for a better understanding of how norepinephrine transmission may recruit BNST-CRF circuitry during chronic alcohol, little is known about how chronic alcohol modulates the source of this norepinephrine signaling. Recent evidence suggests that neurons in the nucleus of the tractus solitarius (NTS) are the main source of norepinephrine transmission in the BNST, but these neurons have yet to be directly examined in the context of alcoholism. The independent phase of this proposal will determine if norepinephrine neurons in the NTS, particularly those neurons that project to the BNST, are modulated by acute and chronic alcohol. This work will set the stage for independent research program aimed at determining how BNST-projecting NTS- norepinephrine neurons regulate alcohol seeking during the development of alcoholism. This integrative approach is a novel way to examine mechanisms of neuropathology in alcoholism and may lead to the development of better treatment strategies to alleviate this debilitating disease.