Jonathan N. Flak

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Chronic stress precipitates pronounced enhancement of central stress excitability, marked by sensitization of hypothalamic-pituitary-adrenocortical (HPA) axis responses and increased adrenocorticotropic hormone (ACTH) secretagogue biosynthesis in the paraventricular nucleus of the hypothalamus (PVN). Chronic stress-induced enhancement of HPA axis(More)
Hypoglycemia engenders an autonomically mediated counterregulatory (CR)-response that stimulates endogenous glucose production to maintain concentrations within an appropriate physiological range. Although the involvement of the brain in preserving normoglycemia has been established, the neurocircuitry underlying centrally mediated CR-responses remains(More)
The goal of this study was to explore mechanisms that mediate hypersecretion of LH and progressive loss of cyclicity in female sheep exposed during fetal life to excess testosterone. Our working hypothesis was that prenatal testosterone excess, by its androgenic action, amplifies GnRH-induced LH (but not FSH) secretion and, thus, hypersecretion of LH in(More)
An emerging literature attests to the ability of psychological stress to alter the inflammatory cytokine environment of the body. While the ability of stress to cause cytokine release is well established, the neural pathways involved in this control have yet to be identified. This study tests the hypothesis that IL-6 neurons of the(More)
Proper integration and execution of the physiological stress response is essential for maintaining homoeostasis. Stress responses are controlled in large part by the paraventricular nucleus (PVN) of the hypothalamus, which contains three functionally distinct neural populations that modulate multiple stress effectors: (1) hypophysiotrophic PVN neurons that(More)
BACKGROUND Stress-related disorders (e.g., depression) are associated with hypothalamic-pituitary-adrenocortical axis dysregulation and prefrontal cortex (PFC) dysfunction, suggesting a functional link between aberrant prefrontal corticosteroid signaling and mood regulation. METHODS We used a virally mediated knockdown strategy (short hairpin RNA(More)
Adolescent development is proposed to represent a time of increased susceptibility to stress. During adolescence, the brain demonstrates a high level of plasticity and can be positively or negatively affected by the environment. This study tests the hypothesis that adolescent development is a stage of enhanced vulnerability to chronic stress. Male(More)
Life stress frequently occurs within the context of homeostatic challenge, requiring integration of physiological and psychological need into appropriate hormonal, cardiovascular, and behavioral responses. To test neural mechanisms underlying stress integration within the context of homeostatic adversity, we evaluated the impact of a pronounced(More)
This study elucidates the neural circuits by which circulating angiotensin II (ANGII) acts in the brain to influence humoral and behavioral responses to psychological stressors. To test the hypothesis that systemic ANGII mediates stress responding via the subfornical organ (SFO), we first found that the timing of increased systemic ANGII in response to 60(More)
Chronic variable stress (CVS) exposure modifies the paraventricular nucleus of the hypothalamus (PVN) in a manner consistent with enhanced central drive of the hypothalamo-pituitary-adrenocortical (HPA) axis. As previous reports suggest that post-stress enhancement of norepinephrine (NE) action contributes to chronic stress regulation at the level of the(More)