William E. Cullinan - US grants

DESCRIPTION (Adapted from applicant's abstract): The goal of the present project is to gain an understanding of the role of the brain in the regulatory biology of stress responsiveness, focusing upon homeostatic mechanisms of glucocorticoid secretion. The ability to cope with stress is of fundamental importance to the survival of all organisms, and in mammals is known to involve the HPA axis. Inputs indicative of stress converge upon a chemically distinct collection of neurons located within the PVN; these neurons, which synthesize CRH and other secretagogues, initiate a cascade of events culminating in the adrenocorticotropic hormone (ACTH)-induced release of glucocorticoid hormones from the adrenals. Glucocorticoids have widespread and potent effects throughout the body, readying the organism for changes required for coping. Maintenance of appropriate levels of these steroid hormones is of critical importance to human health, as either too much or too little is deleterious. Dysregulation of the HPA axis has been linked to several forms of psychiatric illness, including major depression, and is thought to contribute to age-related neurodegeneration and cognitive decline. While the brain is involved in the moment-to-moment regulation of glucocorticoid secretion, the specific neural pathways which mediate stress effects remain to be firmly established. The present proposal will examine brain pathways hypothesized to mediate inhibitory and stimulatory components of the stress response, focusing upon PVN afferent systems that utilize the neurotransmitters GABA and glutamate, respectively. These studies will investigate the hypothesis that GABAergic and glutamatergic neuronal circuits regulate the HPA axis through effects exerted upon the stress-integrative CRH neurons of the PVN. The present studies will: (1) establish the roles of GABA and glutamate on the CRH neuron at the level of cellular activation, transcriptional regulation, and secretion, (2) uncover the precise origins of stress-responsive GABAergic and glutamatergic inputs to the PVN, testing their functional impact on multiple parameters of HPA activity, as well as effects in mediating steroid feedback inhibition, and (3) establish the ability of defined circuits to replay effects of limbic structures implicated in HPA activity. An integrated approach to this investigation will be taken, including combinations of pharmacological, biochemical, molecular biological and neuroanatomical methods. The results are expected to reveal brain pathways which serve as key elements of control over basal and stress-induced glucocorticoid secretion, elucidating mechanisms by which these steroid hormones are regulated.

DESCRIPTION (provided by applicant): This proposal requests funds for a confocal imaging system in order to support and enhance the work of NIH funded investigators at Marquette University studying a variety of dynamic cellular systems. These investigators are currently working within two separate departments (Biomedical Sciences and Biology), and seek to bring the powerful capacity of confocal imaging to biological questions of spinal cord network organization and physiology, the neuroprotective effects of neurotrophins on cortical degeneration, and the functional neuroanatomy of neural pathways which regulate the neuroendocrine stress axis. Additional users are currently studying biological aspects of oocyte maturation and spinal cord regeneration following injury. At present there exists no confocal imaging system at Marquette University, with four users currently conducting confocal imaging studies offsite. The acquisition of this system would enable Marquette investigators to bring many advantages of confocal microscopy to bear on scientific questions, including: a) non-invasive optical sectioning of intact cultures with increased resolution, b) elimination of blur at high magnification in dual-fluorescence neuroanatomical connectional studies, and c) determination of the distribution of labeled markers within cells or tissues by quantitative volumetric imaging and reconstruction of serial sets of optical sections. These capacities will enhance and expand the current and future research efforts of these investigators, as well as provide a powerful new tool to the greater Marquette scientific community for future research endeavors. The possibility of a laser scanning confocal imaging system at Marquette University would be met with great enthusiasm and is timely in view of the current expansion of the scientific departments most involved. Acquisition of the instrument would also serve a significant training purpose for Marquette graduate students and post-doctoral research fellows.