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Draft Paper

Here’s a start. I’ll post a longer version soon 


            Angiotensin receptors take part in various activities ranging from cardiovascular functions to behavior. When angiotensin II, a neurotransmitter, binds to AT1 receptor proteins, it causes a conformational change that elicits a response from the cell; in behavior this could be a change in mood or in a cardiovascular system it could be a change in blood pressure. This study is focusing on the cardiopulmonary regulation through these AT1 receptors in specific brain regions. To visualize these specific proteins within the brain regions of interest we developed an immunohistochemical method. Immunohistochemistry (IHC) is a method for visualizing proteins by attaching antibodies to them so that they can be marked. After testing five different protocols on both hindbrain and forebrain regions, we found that using a mounted amplification technique was the most reliable. Once the slices are done with the IHC protocol we can then take images of the regions of interest via a camera mounted to the microscope. Images are acquired at differing magnification depending on the region. ImageJ is then used to analyze the area, the density of the area compared to the background and the number of neurons marked in a specific region. Using this data we can then compare the density of receptors between the hypertensive group, the normotensive group, and the Captopril-treated group to see if there is an up regulation or down regulation of AT1 in correlation to changing blood pressures.



            The renin-angiotensin system (RAS) has always been focused solely on the peripheral systems of the body. This makes sense because all of the needed components of the RAS are found in peripheral organs, i.e. renin is produced by the kidneys, angiotensinogens are synthesized in the liver, etc. but new studies show that all of these components can be localized within the brain itself. To aid in understanding the function of the brain on the RAS, it is useful to have some background information about the classically viewed model of vasoconstriction in the periphery.

           The first component of the renin-angiotensin system is angiotensinogen. This constituent is synthesized and secreted into the blood stream via the liver, and is inactive in this form. When the kidneys produce renin, usually as a response to the sympathetic nervous system (and low water, low blood pressure, and high salt), it breaks apart the molecular structure of the angiotensinogen, thus forming angiotensin I. Angiotensin I, a hormone, is acted upon by an angiotensin converting enzyme (ACE), which is produced by the lungs. ACE converts angiotensin I into angiotensin II and in this final state it can bind to its receptor, termed the angiotensin I receptor, or simply AT1. When angiotensin II binds to its AT1 receptor, it causes the standard signal transduction pathway to elicit a response from the cell. In this system, the response is the constriction of the blood vessels causing the blood pressure to increase.

           This classical model of the RAS has always been taught and reviewed in the periphery but the emerging studies showing a localized RAS in just the brain seem to hold merit. It is hypothesized that all of the components of the RAS that are produced in the peripheral organs are also synthesized within the neuronal cells. The first major constituent mentioned in the RAS was the angiotensinogens and it is hypothesized that astrocytes secrete this compound into the cerebrospinal fluid. It is worth noting that cultured neurons also can excrete angiotensinogens. With the presence of angiotensinogens, only enzymes are needed to carry out the rest of the steps of the RAS, and it is thought that neuronal mRNA carries the code for producing these proteins. The other major players yet to be mentioned are the AT1 receptors, which have been mapped throughout the brain region.

Categories: Uncategorized
  1. Katie Graves
    July 7, 2009 at 12:21 am

    Your paper looks like it’s going really well! I was just wondering on where all of your information is coming from? Have you found enough to fill 2000-2500 words from your experiments, or are you going to be including background research? I’m looking forward to your presentation tomorrow. Good luck with the rest of your paper!

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