행동적 항상성 조절의 신경회로: 섭식 행동과 체온조절 행동 중심으로

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 협동과정 뇌과학전공, 2022. 8. 김성연.Maintaining physiological conditions (e.g., nutrients, water, and body temperature) within a narrow range is a distinct quality of living organisms. Among them, animals utilize diverse behaviors to suffice materials in need to maintain internal stability, called homeostasis. As such, understanding the neural mechanisms for behavioral regulations of homeostatic conditions has been a key interest in neurobiology and physiology. However, despite the importance of this question, neural processes underlying some of the fundamental behaviors for maintaining organismal homeostasis are still elusive. In this dissertation, I describe the data revealing neural circuit mechanisms underlying two basic behaviors for regulating homeostasis: ingestive and thermoregulatory behaviors. Chapter one of this dissertation briefly overviews the origin of the homeostasis concept and provides a short historical perspective on studying neural processes for behavioral regulation of homeostasis. Chapter two describes a molecularly defined neural population in a hindbrain area called the parabrachial nucleus for monitoring and suppressing ingestion and demonstrates a gut-to-brain neural circuit spanning from the peripheral sensory ganglia to the hypothalamus for mechanosensory feedback control of ingestion. Chapter three describes a parabrachial-to-hypothalamic neural circuit for thermoregulatory behaviors and the neural coding of motivational aspects of thermal stimuli by a subpopulation of hypothalamic neurons. Chapter four describes a summary of the data presented in this dissertation and provides directions for further investigations. Together, this dissertation presents studies on understanding neural circuit mechanisms underlying fundamental behaviors for regulating crucial homeostatic conditions, including energy, fluid, and body temperature.영양분과 체온 등 체내 환경을 일정 수준으로 유지하는 성질인 항상성은 생명체의 중요한 특징이다. 여러 생물 종 중에서 특별히 동물들은 행동을 통해 자신의 필요를 채워 체내 항상성을 유지하는데, 따라서 항상성을 유지하기 위한 동물 행동을 매개하는 신경 기작을 이해하는 것은 신경생물학 및 생리학의 오랜 과제였다. 수십 년에 걸친 연구들로 많은 부분이 밝혀졌으나, 몇몇 근본적인 항상성 유지 행동을 매개하는 신경회로 기작은 여전히 알려지지 않고 있었다. 본 연구는 섭식 행동과 체온 유지 행동을 조절하는 데 관여하는 새로운 신경회로 기작을 밝힘으로써, 항상성 유지의 신경학적 원리에 대한 이해를 넓히는 것을 목표로 한다. 1장에서는 항상성 개념의 형성과 그 이후 이어진 항상성 조절 신경 기작에 관한 연구의 역사를 간략히 살펴보고자 한다. 2장에서는 소화관의 물리적 감각 신호를 이용하여 섭식을 모니터링하고 이에 따라 음식물의 섭취를 조절하는 후뇌부 신경세포 집단과, 그 집단을 중심으로 말초 신경절에서 시상하부까지 이어지는 장-뇌 신경회로에 관한 연구를 기술한다. 3장에서는 다양한 체온조절 행동에 필수적인 시상하부 신경 집단과 이를 중심으로 체온 조절 행동을 매개하는 신경회로 기작에 관한 연구를 기술한다. 4장에서는 본 논문에 기술된 연구 결과를 간략히 정리하고 그 의의에 관해 살펴본다. 본 연구들은 섭식 행동과 체온 조절 행동을 매개하는 신경회로 기작에 관한 새로운 이해를 더함으로써, 생명 유지에 필수적인 항상성 조절 행동의 신경학적 기반을 완전히 밝히는 데 기여할 것으로 기대한다.Chapter 1. Introduction 1 Chapter 2. A neural circuit mechanism for mechanosensory feedback control of ingestion 6 Chapter 3. A forebrain neural substrate for behavioral thermoregulation 80 Chapter 4. Conclusion 167 Bibliography 173 Abstract in Korean 186박

Neurophysiological characterisation of neurons in the rostral nucleus reuniens in health and disease.

Evidence is mounting for a role of the nucleus reuniens (Re) in higher cognitive function. Despite growing interest, very little is known about the intrinsic neurophysiological properties of Re neurons and, to date, no studies have examined if alterations to Re neurons may contribute to cognitive deficits associated with normal aging or dementia. Work presented chapter 3 provides the first detailed description of the intrinsic electrophysiological properties of rostral Re neurons in young adult (~5 months) C57-Bl/6J mice. This includes a number of findings which are highly atypical for thalamic relay neurons including tonic firing in the theta frequency at rest, a paucity of hyperpolarisation-activated cyclic nucleotide–gated (HCN) mediated currents, and a diversity of responses observed in response to depolarising current injections. Additionally this chapter includes a description of a novel form of intrinsic plasticity which alters the functional output of Re neurons. Chapter 4 investigates whether the intrinsic properties of Re neurons are altered in aged (~15 month) C57-Bl/6J mice as compared to a younger control group (~5 months). The intrinsic properties were remarkably similar across age ranges suggesting that alterations to the intrinsic properties of Re neurons do not contribute to age-related cognitive deficits. Chapter 5 investigates whether alterations to the intrinsic properties of Re neurons occur in the J20 model of amyloidopathy. Alterations to the resting membrane potential (RMP), propensity to rebound fire, and a reduction in action potential (AP) width were observed. This suggests that alterations to the intrinsic properties of Re neurons may contribute to cognitive deficits observed in Alzheimer’s disease (AD). Chapter 6 investigates whether alterations to the intrinsic properties of Re neurons occur in a mouse model (CHMP2Bintron5) of frontotemporal dementia (FTD). Only subtle changes were observed suggesting that alterations to the intrinsic properties of Re neurons does not contribute to cognitive deficits observed in FTD linked to chromosome 3 (FTD-3)

Thalamus gates the coding of salient experiences in the hippocampus.

Detecting and responding to emotionally salient stimuli is essential for adaptive behavior. The ventral hippocampus (vHPC) has been implicated in the evaluation of environmental threats and rewards, but the mechanisms by which upstream input modulates hippocampal encoding of salience remain incompletely understood. In this dissertation, I investigated the circuit architecture, input modulation, and neural dynamics that confer salience processing within the vHPC. Across five chapters, I work to define the organizational principles and functional role of these circuits in regulating emotionally charged behaviors.In the first set of studies, I used high-throughput projection mapping techniques, retrograde tracing, and transcriptome profiling to define the molecular and anatomical organization of vHPC projection neurons. These experiments revealed that the majority of vHPC neurons are segregated into distinct projection-defined subpopulations that target limbic structures with a significant proportion of broadcasting neurons that collateralize to multiple areas especially the lateral septum. Furthermore, I identified several biased upstream inputs onto specific vHPC neurons and differential gene expression suggesting vHPC neurons form defined cell types beyond projection target. Building on this framework, I next explored the role of a biased input from the thalamus in shaping vHPC activity. Using 1- and 2-photon in vivo calcium imaging during behavior, combined with chemogenetic inhibition of paraventricular thalamus (PVT) projections to vHPC, I found that thalamic input dynamically modulates the encoding of salient stimuli. Disrupting PVT→vHPC (PVTvHPC) communication impaired both behavioral discrimination and the emergence of salience-specific neural representations, highlighting a critical role for thalamic afferents in guiding hippocampal salience processing.Together, these findings support a model in which ventral hippocampal output neurons are organized into discrete, projection-specific modules, and salience representations within these modules are actively gated by dynamic thalamic input. These results revise classical circuit models of hippocampal function and suggest new mechanistic frameworks for understanding the neural basis of anxiety, depression, and other disorders of maladaptive salience evaluation

Phosphorylation of pyruvate dehydrogenase inversely associates with neuronal activity.

For decades, the expression of immediate early genes (IEGs) such as FOS has been the most widely used molecular marker representing neuronal activation. However, to date, there is no equivalent surrogate available for the decrease of neuronal activity. Here, we developed an optogenetic-based biochemical screen in which population neural activities can be controlled by light with single action potential precision, followed by unbiased phosphoproteomic profiling. We identified that the phosphorylation of pyruvate dehydrogenase (pPDH) inversely correlated with the intensity of action potential firing in primary neurons. In in vivo mouse models, monoclonal antibody-based pPDH immunostaining detected activity decreases across the brain, which were induced by a wide range of factors including general anesthesia, chemogenetic inhibition, sensory experiences, and natural behaviors. Thus, as an inverse activity marker (IAM) in vivo, pPDH can be used together with IEGs or other cell-type markers to profile and identify bi-directional neural dynamics induced by experiences or behaviors

Brain Struct Funct

Opioid receptors are G protein-coupled receptors (GPCRs) that modulate brain function at all levels of neural integration, including autonomic, sensory, emotional and cognitive processing. Mu (MOR) and delta (DOR) opioid receptors functionally interact in vivo, but whether interactions occur at circuitry, cellular or molecular levels remains unsolved. To challenge the hypothesis of MOR/DOR heteromerization in the brain, we generated redMOR/greenDOR double knock-in mice and report dual receptor mapping throughout the nervous system. Data are organized as an interactive database offering an opioid receptor atlas with concomitant MOR/DOR visualization at subcellular resolution, accessible online. We also provide co-immunoprecipitation-based evidence for receptor heteromerization in these mice. In the forebrain, MOR and DOR are mainly detected in separate neurons, suggesting system-level interactions in high-order processing. In contrast, neuronal co-localization is detected in subcortical networks essential for survival involved in eating and sexual behaviors or perception and response to aversive stimuli. In addition, potential MOR/DOR intracellular interactions within the nociceptive pathway offer novel therapeutic perspectives

Novel therapeutic strategies in NBIA: A gene therapy approach for PLA2G6-associated neurodegeneration

Infantile neuroaxonal dystrophy (INAD) is a debilitating, intractable and ultimately lethal neurodegenerative disorder. It is caused by mutations in the PLA2G6 gene which encodes for phospholipase A2. INAD patients present neurodegeneration-associated symptoms between six months and three years of age. Severe spasticity, progressive cognitive decline, and visual impairment typically result in death during the first decade (Morgan et al, 2006). There is no disease-modifying treatment available and palliative care focuses on quality of life. Therefore, there is an overwhelming need to develop novel therapies to treat INAD patients. To create a landscape of the behavioural and pathological deficits, we aim to first conduct an in-depth characterization of the PLA2G6 mouse model developed by Wada et al (2009). Additionally, we aim to develop an AAV-mediated gene therapy approach for the treatment of INAD and conduct a pre-clinical study in the pla2g6-inad mouse model. The objective is to be able to prevent or ameliorate both the central and peripheral nervous system phenotype and improve the lifespan and/or quality of life of the animal. Recombinant adeno-associated virus serotype 9 vector (AAV9) will be used to deliver the therapeutic human PLA2G6 gene to the neonatal pla2g6-inad mouse. The strong neuron specific synapsin-I promoter will drive the human PLA2G6 gene. The efficacy of different administration routes including intracerebroventricular (ICV), intravenous (IV) and a combination of intracerebroventricular (ICV)/ intravenous (IV) and intracerbroventricular (ICV)/intraperioteneal (IP) will be investigated in the pla2g6-inad mouse model. AAV9-hSyn1-hPLA2G6 gene therapy treated pla2g6-inad mice showed an increased lifespan with the largest improvements observed in the animal cohort that received a combined administration of AAV9-hPLA2G6. The significant increase in lifespan supplemented with significant improvements in behavioural tests validates the potential beneficial use of gene therapy for infantile neuroaxonal dystrophy (INAD)

Primate Ventromedial Prefrontal Cortex and the Physiological and Behavioural Dysfunction Characteristic of Mood and Anxiety Disorders

The heterogeneity intrinsic to the ventromedial prefrontal cortex (vmPFC) is evidenced in both its anatomy and implicated function: vmPFC subregions have roles in positive affect, negative affect and autonomic/endocrine regulation. Whether different subregions serve fundamentally different functions, or whether they perform similar computations on different inputs, remains unclear. Nevertheless, the role of the vmPFC in psychopathology is widely appreciated – in mood and anxiety disorders, over-activity within constituent regions of the vmPFC is consistently implicated in symptomatology, together with its normalisation following successful treatment. However, the precise locus of change varies between studies. The work presented in this thesis investigates the causal contributions of over-activity within two key subregions of the vmPFC – the subgenual anterior cingulate cortex (sgACC, area 25) and perigenual anterior cingulate cortex (pgACC, area 32) – in discrete dimensions of behaviour and physiology affected in psychiatric disorders. Specifically, the impact of over-activity is assessed on (i) baseline physiological function; (ii) the regulation of anticipatory, motivational and consummatory aspects of reward-related behaviour; and (iii) negative affect including fear learning, stress recovery and the intolerance of uncertainty. To provide further insight into the mechanism of action of antidepressants, the efficacy of selected treatments is tested on changes induced by over-activity of these regions. Beyond the direct relevance of the results presented here to psychiatric disorders and their treatment, the thesis aims to emphasise the importance of broader themes associated with the measurement and quantification of emotion in preclinical animal studies. First, a multi-faceted approach is utilised enabling quantification of both the autonomic and behavioural aspects of emotion. In so doing, the experiments maintain relevance to studies which assess these correlates in isolation, both in humans (which typically measure subjective responses and physiology) and in rodents (which frequently assess behaviour in isolation). The assessment of more than one dimension of emotion confers these studies with improved power to detect maladaptive changes. Second, the experiments described were conducted in the marmoset, a new-world primate. The extensive anatomical homology between marmoset and human prefrontal cortex facilitates the forward-translation of functional results. In combination with the appropriate assays, this renders marmosets as an invaluable species to study the causal contributions of vmPFC subregions to symptoms of psychiatric disorders. I believe that the results of these experiments provide important insights into the causal role primate vmPFC has in relation to the behavioural and physiological aspects of psychiatric symptomatology. Most importantly, I hope that they serve as the foundation for future work to further elucidate the neuropathological processes underlying mental disorders.MRC DTP Studentshi