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Rossi N.F.,Wayne State University | Rossi N.F.,John ngell Veterans Administration Medical Center | Maliszewska-Scislo M.,Wayne State University | Chen H.,Wayne State University | And 5 more authors.
Experimental Physiology

The renin-angiotensin system is activated in the early phase of two-kidney, one-clip (2K-1C) hypertension. The paraventricular nucleus (PVN) integrates inputs regulating sympathetic outflow. The PVN receives inputs from plasma angiotensin II via projections from circumventricular organs and from renal afferent nerves transmitted via the nucleus tractus solitarii. Nitric oxide within the PVN may exert a sympathoinhibitory effect. These studies tested whether decreasing endogenous nitric oxide by introducing dominant negative (DN) constructs for neuronal nitric oxide synthase (nNOS) into PVN chronically augments hypertension and/or modulates baroreflex function. Male 6-week-old Sprague-Dawley rats underwent sham surgery or right renal artery clipping and placement of radiotelemetry transmitters. One week later, the PVN was injected bilaterally with 250 nl artificial cerebrospinal fluid containing 250 ng μl-1 of RSV β-galactosidase (β-Gal), cytomegalovirus (CMV) wild-type (WT nNOS), or respiratory syncytial virus (RSV) haeme domain or RSV haemeRedF (DN nNOS). Haemodynamics were monitored for 5 weeks. Then left renal nerve electrodes were placed, and 2 days later the rats underwent baroreflex testing in the conscious state. The rise in mean arterial pressure (MAP) was significantly potentiated in the DN nNOS 2K-1C group beyond 15 days after PVN injection. By day 35, MAP in the 2K-1C groups was 152 ± 6.3 (β-Gal), 155.1 ± 6.6 (WT nNOS) and 179 ± 5.4 mmHg (DN nNOS; P < 0.01 versus all other groups). Sham-clipped rats remained normotensive. All groups displayed progressive bradycardia over time that was attenuated in the DN nNOS 2K-1C group. Baroreflex curves shifted to higher pressures, and baroreflex sensitivity of heart rate was diminished to a similar extent in all groups of 2K-1C rats. The baroreflex response of renal sympathetic nerve activity was preserved. The PVN tissue from DN nNOS rats had decreased dimerization of nNOS and generation of total nitric oxide. These findings indicate that chronic interference of nNOS dimerization required for generation of nitric oxide within the PVN potentiates the increase of blood pressure by modulating the sympathoexcitation that accompanies renovascular hypertension. © 2010 The Physiological Society. Source

Mateika J.H.,Wayne State University | Mateika J.H.,John ngell Veterans Administration Medical Center | Sandhu K.S.,Wayne State University | Sandhu K.S.,John ngell Veterans Administration Medical Center
Respiratory Physiology and Neurobiology

Respiratory long-term facilitation is a form of neuronal plasticity that is induced following exposure to intermittent hypoxia. Long-term facilitation is characterized by a progressive increase in respiratory motor output during normoxic periods that separate hypoxic episodes and by a sustained elevation in respiratory activity for up to 90 min after exposure to intermittent hypoxia. This phenomenon is associated with increases in phrenic, hypoglossal or carotid sinus nerve inspiratory-modulated discharge. The examination of long-term facilitation has been steadily ongoing for approximately 3 decades. During this period of time a variety of animal models (e.g. cats, rats and humans), experimental preparations and intermittent hypoxia protocols have been used to study long-term facilitation. This review is designed to summarize the strengths and weaknesses of the models, preparations and protocols that have been used to study LTF over the past 30 years. The review is divided into two primary sections. Initially, the models and protocols used to study LTF in animals other than humans will be discussed, followed by a section specifically focused on human studies. Each section will begin with a discussion of various factors that must be considered when selecting an experimental preparation and intermittent hypoxia protocol to examine LTF. Model and protocol design recommendations will follow, with the goal of presenting a prevailing model and protocol that will ultimately ensure standardized comparisons across studies. © 2011. Source

Sajja V.S.S.S.,Wayne State University | Galloway M.P.,Wayne State University | Ghoddoussi F.,Wayne State University | Thiruthalinathan D.,Wayne State University | And 5 more authors.
NMR in Biomedicine

Blast-induced neurotrauma is a major concern because of the complex expression of neuropsychiatric disorders after exposure. Disruptions in neuronal function, proximal in time to blast exposure, may eventually contribute to the late emergence of clinical deficits. Using magic angle spinning 1H MRS and a rodent model of blast-induced neurotrauma, we found acute (24-48 h) decreases in succinate, glutathione, glutamate, phosphorylethanolamine and γ-aminobutyric acid, no change in N-acetylaspartate and increased glycerophosphorylcholine, alterations consistent with mitochondrial distress, altered neurochemical transmission and increased membrane turnover. Increased levels of the apoptotic markers Bax and caspase-3 suggested active cell death, consistent with increased FluoroJade B staining in the hippocampus. Elevated levels of glial fibrillary acidic protein suggested ongoing inflammation without diffuse axonal injury measured by no change in β-amyloid precursor protein. In conclusion, blast-induced neurotrauma induces a metabolic cascade associated with neuronal loss in the hippocampus in the acute period following exposure. © 2012 John Wiley & Sons, Ltd. Source

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