Project Summary: The primary goal of this training proposal is to dissect the neurocircuitry of locus coeruleus (LC) noradrenergic projections to the dentate gyrus (DG) in contextual memory processing. Previous research has implicated this circuit in aversive contextual processing, with increased norepinephrine (NE) resulting in impaired discrimination in learning the difference between a safe context and an unsafe context. These findings point to this circuits relevance to disorders such as post-traumatic stress disorder (PTSD), and schizophrenia, both of which are characterized by failures in memory, specifically in pattern separation. However, many more questions remain regarding the exact circuit, cell-type, and molecular mechanisms by which this occurs. The first aim of this training proposal seeks to characterize the spatiotemporal dynamics of norepinephrine release in the DG during aversive contextual processing. Aim 1A uses fiber photometry in conjunction with newly developed NE-sensors to observe endogenous NE release during aversive and novel stimuli, while Aim 1B uses fiber photometry in conjunction with photo-stimulation to test for sufficiency of evoked NE release in pattern separation in place of aversive stimuli in a neutral context. The second aim of this training proposal seeks to elucidate the mechanisms by which NE acts on α- and β-adrenergic receptors (ARs) in the dentate gyrus during aversive contextual processing. Aim 2A uses in vitro 2-photon calcium imaging and slice electrophysiology with application of AR- specific pharmacological agents to determine the role of α- and β-ARs on specific cell types in modulating DG excitability properties, while Aim 2B uses CRISPR-based viral techniques to selectively knockout α- and β-ARs in the DG during in vivo 1-photon calcium imaging to determine the effects of α- and β-ARs on DG neural ensemble shifts during aversive contextual processing. Using these techniques will allow me to uncover the distinct mechanisms by which α and β-ARs modulate DG neuron excitability and neural ensemble changes to affect aversive contextual processing. Here we utilize in vivo and in vitro calcium imaging in the dentate gyrus, fiber photometry in the dentate gyrus, and selectively knockout α- and β-ARs to further understand the role of the LC-DG noradrenergic circuit and its role in aversive contextual processing. Leveraging these numerous, novel, high-resolution approaches will allow us to further understand the endogenous noradrenergic system and identify potential mechanisms that underlie PTSD and schizophrenia. During my tailored mentored training period, I will learn fiber photometry, 2-photon calcium imaging, in vitro slice electrophysiology, CRISPR-based viral, pharmacological, computational, and behavioral techniques, as well as fully engage into a specific mentored development plan to prepare me for an independent research career.

Project Narrative: Approximately 3% of the adult population suffers from PTSD at any one time, while the prevalence of schizophrenia approaches 1% internationally. These disorders typically result from failures in contextual processing and pattern separation, both components of learning and memory. The goal of this proposal is to leverage modern neurobiological approaches and gain mentored training to determine how the locus coeruleus to dentate gyrus noradrenergic circuit drives pattern separation during aversive contextual processing, identifying potential new avenues for treatment of stress- and memory-related disorders.