Robert Spencer - US grants

Much of our present understanding of the neuronal and synaptic organization of the oculomotor system has evolved from morphological, physiological, and clinicopathological studies of the neurones, nuclei, and pathways that are related to various types of eye movement. The correlation of the neuronal activity of premotor neurones with the activity of both the oculomotor motoneurones and the extracular muscles suggests synaptic relationships that underly neuronal interactions in the oculomotor system, particularly in the vestibulo-ocular reflex. The specific aims of the proposed studies are directed toward delineating similarities and/or differences in the patterns of synaptic connectivity of second-order vestibular neurones with motoneurones in the oculomotor, trochlear, and abducens nuclei. Physiologically-identified second-order vestibular neurones or axons will be identified electrophysiologically and stained by intracellular injection of horseradish peroxidase, and their axonal arborizations will be reconstructed by light and electron microscopy to determine the modes and patterns of synaptic connections with different populations of motoneurons. In addition, the postnatal development of abducens motoneurones and internuclear neurones and of the lateral rectus muscle will be examined by electron microscopy in relation to the synaptic inputs to the neurones and the sequential differentiation of different muscle fiber types. The proposed studies are consistent with the long-term goal of elucidating neuronal and synaptic relationships in the oculomotor system underlying gaze and their relationship to disorders of ocular motility.

DESCRIPTION (Adapted from applicant's abstract): Much of our present understanding of the oculomotor system has evolved from morphological, physiological, and clinicopathological studies of the neurons, nuclei, and pathways that are related to various types of eye movement. Certain fundamental principles regarding motoneuronal organization in the oculomotor system have been elucidated to the extent that the soma-dendritic profiles, synaptic organization, and afferent and efferent connections of motoneurons in the extraocular motor nuclei are now well defined and differ according to brainstem location and their role in horizontal or vertical eye movements. Over the past decade, considerable knowledge also has accumulated regarding the putative neurotransmitters that are utilized by excitatory and inhibitory premotor neurons in the oculomotor system. However, a critical gap exists in the knowledge of the neurotransmitter receptors that are associated with the synaptic connections in the brainstem oculomotor system, particularly those of second-order vestibular inputs to motoneurons in the extraocular motor nuclei. The major emphasis of the proposed studies is directed toward continued studies of neurotransmitter utilization in the brainstem oculomotor system, specifically in regard to the neurotransmitters and their receptors that are associated with the vestibular inputs to motoneurons in the oculomotor, trochlear, and abducens nuclei, as well as in the cervical spinal cord, as they relate to the control of horizontal and vertical gaze. The overall purpose of these studies is to determine if neurotransmitter differences exist between different populations of second-order vestibular neurons (e.g., vestibulo-ocular, vestibulo-collic, vestibulo-oculo-collic) that might be related to known differences in their physiological activity in relation to the control of eye movement versus head movement and/or gaze. Another major goal of the proposed studies is to determine the extent to which the neurotransmitters and receptors of second-order vestibulo-ocular and vestibulospinal neurons are regulated during development in the kreisler mouse, a genetic mutant strain in which specific rhombomeres in the embryonic hindbrain are absent. The specific aims of this research are consistent with the long-term goal of understanding the neuronal and synaptic organization of the oculomotor system underlying the control of gaze and the sequelae, both central and peripheral, of neurological disorders that are characterized by deficits in ocular motility.

DESCRIPTION (provided by applicant): Glucocorticoid hormones have powerful multifactorial regulatory effects on every physiological system. Dysregulated patterns of glucocorticoid hormone secretion, often as a result of chronic stress, have adverse effects on physical and mental health. Dysregulation of glucocorticoid secretion is strongly associated with some psychological disorders (e.g. depression and posttraumatic stress disorder) and other biomedical disorders (e.g. Type II diabetes, chronic fatigue syndrome, fibromyalgia). Glucocorticoid secretion is controlled by the neuroendocrine hypothalamic-pituitary-adrenal (HPA) axis system, and the principal factor that has regulatory control over HPA axis activity is glucocorticoid negative feedback. Understanding of the mechanisms responsible for glucocorticoid negative feedback is limited. To address that gap in knowledge, this ongoing research project will determine the molecular, cellular and systems level mechanisms of glucocorticoid negative feedback. This knowledge is necessary to discern how chronic stress leads to altered glucocorticoid negative feedback function, and it will point to new strategies for targeted interventions that will prevent and perhaps reverse alteration of glucocorticoid negative feedback function associated with chronic stress. The guiding hypothesis of this project is that glucocorticoids produce multiple effects within the intrinsic anatomical elements of the HPA axis as well as effects on neural circuits that dictate the moment-to-moment HPA axis activity. These glucocorticoid effects have distinct time frames of onset and expression, as well as separate underlying molecular mechanisms. By establishing these cellular sites of action and temporal patterns of expression this project will determine specific mechanisms of glucocorticoid negative feedback. Previous work on this project identified independent actions of glucocorticoids that are evident within different time intervals after a phasic increase in glucocorticoids that can be distinguished as fast (<15 min), short-term (~ 1 hr), and delayed (~3 hr) negative feedback actions. Four Specific Aims organized around this conceptual framework will address the following: Aim 1] To determine the temporal requirements and receptor mechanisms by which glucocorticoids produce fast negative feedback at the hypothalamic paraventricular nucleus. Aim 2] To use hypothalamic organotypic cultures to determine cellular and molecular mechanisms by which glucocorticoids produce intrinsic negative feedback on CRH neurons. Aim 3] To determine in vivo mechanisms of glucocorticoid short-term and delayed negative feedback. Aim 4] To determine the relationship between chronic stress adaptation and glucocorticoid negative feedback function. The new information derived from these proposed studies can then be applied to 1) the design of better (more sensitive or revealing) HPA axis related measures and challenge conditions in patient populations, 2) identification of new candidate risk genes associated with HPA axis dysregulation, and 3) development of new treatments that may selectively normalize HPA axis function without disturbing appropriate glucocorticoid signaling throughout the body.

DESCRIPTION (provided by applicant): Stress is a leading presenting, precipitating and exacerbating factor for a wide array of biomedical pathological conditions, with an especially strong etiological link with mental disorders. Researchers have made significant recent advances in understanding the neurobiology of stress. Determining the molecular, cellular and neurosystems mechanisms through which stress alters brain function is essential to understanding the mechanistic relationship between stress and mental disorders. A Neurobiology of Stress Workshop is being organized to be held June 15-18, 2010 at Boulder Colorado. This rigorous scientific meeting will bring together preclinical and clinical researchers who study stress-brain interactions and their impact on mental and physical health. This Workshop addresses an important need to strengthen the community of stress researchers in a manner that will maximize the productivity and clinical benefit of future stress research. Thus, the Workshop will provide a unique opportunity for researchers to participate in face-to-face examination of recent research advances, to share perspectives, identify relevant issues, debate controversies and exchange diverse expertise. Five sessions are planned in which invited speakers will present new research work, novel ideas, and examination of clinically relevant issues. Session themes are organized around specific stress-related factors and their impact on mental health and disease. Specifically, these stress-related factors of focus are 1) energy metabolism, 2) lifespan epochs, 3) risk factors, 4) resistance/resilience factors, and 5) cognitive and emotional factors. One of the five sessions is a targeted multidisciplinary cross-fertilization session featuring metabolism/energy balance and its relationship with stress neurobiology. In addition to the discussion time within each session, the Workshop features extensive time for interaction among all attendees at the opening data blitz reception, shared daily lunch period, Poster Session, and a social hour that will feature an informal discussion of the future of stress research. A priority of the Workshop is to foster the professional development of new investigators and women by including them at all levels of meeting organization and Program participation. Further the Workshop will nurture career development of graduate students and postdoctoral researchers by giving them ample opportunity to participate in the Workshop via the data blitz session, Poster Session, discussion sessions, "Meet the Speaker" luncheon roundtables, and an on-line Meeting Issues Blog. Travel Grants will be made available to select trainees through a merit based application process, with a detailed plan in place to recruit applications from interested minority candidates. Funds are requested in this application to support Trainee Travel Grants, Poster Session costs, and meeting related costs for new investigators, women and minorities that are participating in the Scientific Program. This Workshop will address critical needs in the stress research community that are ongoing, and consequently we envision this meeting as serving as a model for a recurring series of Stress Workshops. PUBLIC HEALTH RELEVANCE: The adverse effects of stress on mental and physical health has come to the fore as one of the most pressing biomedical problems in our society. The proposed Neurobiology of Stress Workshop to be held June 15-18, 2010 in Boulder Colorado will bring together basic, preclinical and clinical researchers and affiliated trainees in order to significantly enhance the productivity and clinical benefit of future stress research.

Arctic-GRO Non-Technical Abstract

Massive northern rivers transport huge quantities of freshwater, carbon, and other compounds from the continents to the Arctic Ocean. The overarching scientific rationale for the Arctic Great Rivers Observatory (Arctic-GRO) is that large river hydrology and chemistry can be used to assess changes in fluxes that signal regional and pan-arctic change on the continents and that subsequently impact coastal and ocean chemistry, biology, and circulation. The watersheds of the six Arctic-GRO rivers are among the largest on Earth and combined cover 11,400,000 km2, more than half of the area that drains into the Arctic Ocean. Given that the biogeochemistry of rivers integrates processes occurring throughout their watersheds, Arctic-GRO?s systematic sampling of the downstream reaches of the Ob?, Yenisey, Lena, and Kolyma rivers in Siberia, and the Yukon and Mackenzie rivers in North America, provides a superb means for assessing environmental change in the Arctic.

A variety of activities will be pursued to ensure that Arctic-GRO has substantial broader impacts. These activities will include 1) the maintenance and enhancement of a project website, www.arcticgreatrivers.org, 2) the production and widespread distribution of two multimedia videos about Arctic-GRO and the Arctic Observing Network, 3) an exchange between indigenous people in the Yukon and Lena river watersheds, in partnership with the Yukon River Inter-tribal Watershed Council, and 4) the expansion of a traveling art exhibition that tells the story of climate change and its impact in the Arctic, featuring artwork done by indigenous children from the Siberian and North American Arctic.

Psychiatric disorders, especially those marked by dysregulated mood and emotional control, such as depression, bipolar disorder, post traumatic stress disorder (PTSD) and schizophrenia, are associated with physiological and cognitive features of disrupted circadian function. Circadian regulation is necessary for appropriate anchoring of the optimal performance of virtually every cell and system of the body to fluctuating daily demands. Although the suprachiasmatic nucleus (SCN) of the hypothalamus serves as the body?s master circadian pacemaker, cells in other brain regions and in peripheral tissues express many of the same molecular clock elements (i.e. clock genes) as those found in the SCN. Recent advances have been made in determining the functional role and regulation of cellular clocks in peripheral tissues. Those studies demonstrate an important circadian entraining influence of the endogenous glucocorticoid hormones (CORT) on peripheral tissue cellular clock function. However, there is very little understanding of the function and regulatory processes of cellular clocks in extra-SCN brain regions. The prefrontal cortex (PFC) is a brain region that plays a central role in organizing and coordinating physiological, behavioral and emotional responses. Animal and human studies show that there is rhythmic clock gene expression in the PFC. Recent studies have found that normal clock gene expression in the PFC of rats depends on appropriate profiles of CORT secretion. Moreover, disruption of CORT-entrained PFC clock gene expression results in impaired diurnal patterns of conditioned fear extinction memory. PTSD is associated with impaired circadian function, compromised PFC function and dysregulation of CORT secretion. In addition, individuals with PTSD suffer from persistent conditioned fear responses. Improving conditioned fear extinction learning is a primary therapeutic objective for treating PTSD. Consequently, this project will use a rat animal model to determine the mechanistic basis by which PFC clock gene expression and CORT interdependently regulate conditioned fear extinction memory. The project is organized around 3 specific aims: Aim 1] To determine how time of day, circadian CORT and ventral medial PFC (vmPFC) clock gene expression modulate the activity of neuronal projections from the vmPFC to the basal medial amygdala (BMA) during conditioned fear extinction training and recall. Aim 2] To determine how time of day, circadian CORT and vmPFC clock gene expression modulate neuroplasticity- related processes in the vmPFC that support conditioned fear extinction recall. Aim 3] To test the necessity and sufficiency of vmPFC to BMA projections for mediating time of day, circadian CORT and vmPFC clock gene expression regulation of conditioned fear extinction recall. The proposed studies will provide new understanding of how circadian and CORT factors dynamically interact to regulate PFC function. These studies will also lead to better understanding of the underlying mechanisms of conditioned fear extinction memory, a neuroprocess that has important clinical relevance for circadian and stress-related disorders.