Hypertensive Study
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ABSTRACT: Animals. Male Sprague–Dawley rats (Charles River Laboratories, Wilmington, MA) weighing about 250g were used. The study was approved by the Thomas Jefferson University Institutional Animal Care and Use Committee and was conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals. The animals were housed in Thomas Jefferson University's animal care facilities. Animals were anesthetized with isoflurane dissolved in O2 (5% induction; 1% maintenance) and one femoral artery and vein were cannulated (PE-50 tubing) via a small medial incision for measurement of arterial pressure and infusion of drugs, respectively. The cannulae were run subcutaneously to an exit incision between the scapulae. The leg wound was sutured and topical anesthetic (lidocaine) was applied to both skin incisions. Following surgery, after one hour of stable and normal resting blood pressure and heart rate, intravenous infusion was initiated of approximately 1 mL saline, as a control, or phenylephrine (200 µg/mL; 1 mL/hr), to induce hypertension. We followed standard methods in the use of phenylephrine (PE) to elevate blood pressure. PE does not cross the blood brain barrier and the elevated blood pressure it produces has been shown to cause molecular effects in the NTS principally via increased baroreceptor afferent drive by both pharmacological and sinoaortic denervation studies. We titered the PE dose to maintain intermediate levels of elevated blood pressure 25 mmHg above resting blood pressure. Keywords: Hypertension, time series In keeping with practice of previous studies we induced a defined period of hypertension and then measured effects on the NTS at time points following that standard period of blood pressure disturbance. The previous studies show that blood pressure elevations of 25-30mmHg above baseline induce c-fos expression in the NTS after 30-40 minutes. Based on this result, we estimated that transcriptional regulation in the NTS might be observed after 60 minutes. For this reason we used a standard 60 minute acute hypertension experimental treatment. We took the first samples immediately after the 60 minutes of PE or saline infusion at 15 minute intervals. Our experimental design is for time series data at 60, 75, 90, 105 and 120 minutes (see Figure 1). Gas anaesthesia has previously been reported to induce p-ERK1/2 phosphorylation in some central autonomic structures so the present study reports only differential data that compares to controls that experience the same surgery and fluid (saline) infusion. In order to maximize the statistical power of the experimental design and capture biological variability we did not pool mRNA across animals, but used one array per animal. Four control and four treated animals were taken for each time point and condition for a total of 40 animals. In our previous studies, we found that four replicates in each condition were necessary to accurately and reproducibly measure small, physiologically relevant fold changes as low as 1.2-fold.
ORGANISM(S): unidentified
SUBMITTER: Rishi Khan
PROVIDER: E-GEOD-8585 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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