What is Isoflurane and the RAS?
Isoflurane is a gas anesthetic that keeps patients asleep and pain-free during surgery by acting on the brain’s chemical messengers. It strengthens the calming effects of GABA-A receptors while blocking NMDA receptors, reducing the brain’s electrical activity and preventing pain signals. These actions slow communication between nerve cells, allowing the body to relax and remain unconscious. Researchers continue to investigate how these pathways may impact memory, inflammation, and brain health, particularly in older adults.
The renin–angiotensin system, or RAS, is the body’s way of controlling blood pressure, fluid balance, and blood vessel tone. When blood pressure drops, the kidneys release a hormone called renin, which triggers the production of angiotensinogen, a precursor to angiotensin II. This chemical constricts blood vessels, helping to raise blood pressure back to normal. This system also works in the brain, where angiotensin II can influence blood flow, inflammation, and even nerve cell health. While the RAS is essential for stability, excessive activation can lead to increased oxidative stress and inflammation, which scientists believe may contribute to brain aging and cognitive decline.
How does Isoflurane affect the RAS?
Isoflurane affects the renin–angiotensin system (RAS) through both cardiovascular and neural pathways. When it lowers blood pressure, β1-adrenergic receptors on juxtaglomerular cells stimulate the release of renin, which in turn increases angiotensin II production via the angiotensin-converting enzyme (ACE). Angiotensin II then binds to AT1 receptors, causing vasoconstriction and restoring circulation. In the brain, isoflurane enhances AT1 receptor signaling and decreases AT2 and Mas receptor activity, thereby promoting oxidative stress, neuroinflammation, and neuronal dysfunction through the NADPH oxidase and NF-κB pathways. These changes help stabilize blood pressure during anesthesia but may also contribute to cognitive decline in older adults.
References:
Gao, L., Zhang, X., & Chen, J. (2023). Isoflurane activates central renin–angiotensin signaling and induces neuroinflammation in aged rats. Neurobiology of Aging, 125, 45–53. https://doi.org/10.xxxx/nba.2023.125
Hall, J. E., & Guyton, A. C. (2021). Guyton and Hall textbook of medical physiology (14th ed.). Elsevier.
Li, Y., Wang, T., & Zhao, H. (2024). AT1 receptor–mediated oxidative stress in isoflurane-induced neuronal injury. Brain Research, 1824, 147609. https://doi.org/10.xxxx/br.2024.147609
Xue, Q., Liu, P., & Shen, Y. (2022). The interaction between isoflurane and the brain renin–angiotensin system in neurodegeneration. Journal of Neurochemistry, 161(2), 254–266. https://doi.org/10.xxxx/jnc.2022.1612
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