Prefrontal Cortical Circuitry Attenuates Cardiovascular Stress Reactivity

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DESCRIPTION (provided by applicant): Project Summary This career development award will support my continued training in integrative neuroscience by focusing on the contribution of stress neurobiology to cardiovascular pathophysiology. The funding mechanism also provides a unique opportunity to facilitate the transition to independence. My long-term career goal is to establish an independent academic research program investigating the role of the prefrontal cortex in the generation of abnormal stress responsiveness with an emphasis on cardiovascular health. Determining the mechanisms of cardiovascular stress reactivity is crucial as prolonged or repeated stress represents a prominent risk factor for cardiovascular disease. Additionally, exaggerated physiological reactions to acute stress predict the incidence of cardiovascular disease, as well as cardiac-related morbidity and mortality. However, the specific neural mechanisms that contribute to the cardiovascular consequences of stress are largely unknown. This is an understudied but critical area of research with significant implications for understanding and treating cardiovascular disease, the leading cause of death in the United States. Clinical studies suggest that hypofunctionality of frontal cortical regions affects cardiovascular physiology and our preliminary data demonstrate that genetically-driven decreases in output from the infralimbic prefrontal cortex (IL) exacerbate both cardiovascular and endocrine responses to acute psychological stress in rats. Therefore, the current proposal will explore the mechanisms by which the IL inhibits cardiovascular responsiveness to stress, with the goal of elucidating the neurobiological basis of stress-related disorders such as hypertension and heart disease. The proposed studies will test the overarching hypothesis that IL circuits are necessary for preventing enhanced sympathetic and endocrine responses to stress that promote hypertension, sympathovagal imbalance, and cardiac hypertrophy following chronic stress. Specific Aim 1 will be conducted during the mentored phase and test the hypothesis that decreased glutamate output from the IL is responsible for chronic stress-induced cardiac and vascular pathology. Importantly, all measures related to cardiovascular pathology represent new technical and conceptual training. Lentiviral-mediated gene knockdown will be used to assess the role of IL output in protecting against the sensitization of cardiovascular responses to an unpredictable chronic variable stress regimen. Echocardiography and cardiac histology will be employed to investigate alterations in cardiac function and structure, respectively. Vascular reactivity, inflammatory mediators, and plasma lipids will be assayed to determine the vascular effects of sustained autonomic activation under chronic stress. Training for Specific Aim 2 will occur during the mentored phase and experiments will be completed during the independent phase to test the hypothesis that IL activation is sufficient to restrain cardiovascular output through inhibition of the sympathetic nervous system. To address this hypothesis, optogenetic stimulation of IL projection neurons will be combined with radiotelemetry to measure heart rate, blood pressure, and regional sympathetic nerve activity. Specific Aim 3 will be carried out entirely within the independent phase and test the hypothesis that effects of chronic stress on cardiovascular reactivity can be prevented by stimulating glutamate receptors in downstream pre-sympathetic cardioregulatory regions of the hypothalamus. Optogenetic stimulation of glutamate release at IL terminal sites in the posterior hypothalamus after exposure to CVS combined with glutamate receptor pharmacology will investigate the sufficiency of this circuit for inhibiting the expression of chronic-stress induced sympathovagal imbalance and glucocorticoid hypersecretion. Collectively, these aims examine the cardiovascular consequences of decreased output from prefrontal cortex and determine whether homeostasis can be restored by driving specific neurochemical activation of pre-sympathetic sites in the posterior hypothalamus. The proposed experiments will facilitate advanced training in new technical and conceptual realms, while additional career development activities include technical and grant writing workshops, academic coursework, training events sponsored by the Cardiovascular Center of Excellence, and regular meetings with the career advisory committee. The committee will remain active as mentors through both phases of the award, providing guidance on the transition to an independent position, as well as critiques of initial R01 submissions.