All it takes is the flip of a protein "switch" within the tiny wire-like capillaries of the brain to increase the blood flow that ensures optimal brain function. New research has uncovered that capillaries have the capacity to both sense brain activity and generate an electrical vasodilatory signal to evoke blood flow and direct nutrients to nourish hard-working neurons. These findings were reported online on March 20, 2017 in Nature Neuroscience. The article is titled “Capillary K+-Sensing Initiates Retrograde Hyperpolarization to Increase Local Cerebral Blood Flow.” When there is an increase in brain activity, there is an increase in blood flow, says Thomas Longden, Ph.D., Assistant Professor of Pharmacology at the Larner College of Medicine at the University of Vermont and first author of the study. "The area of the brain covered by the capillaries--the smallest blood vessels in the body -- vastly surpasses the area covered by arterioles. This ideally positions them for monitoring neuronal activity and controlling blood flow." Understanding the mechanisms that precisely direct cerebrovascular blood flow to satisfy the brain's ever-changing energy needs has, to date, eluded scientists. Neurons consume an enormous amount of the body's energy supplies--approximately 20 percent--yet lack their own reserves, so are reliant on blood to deliver nutrients. Previously, capillaries were thought to be passive tubes and the arterioles were thought to be the source of action. Now, Dr. Longden and colleagues have discovered that capillaries actively control blood flow by acting like a series of wires, transmitting electrical signals to direct blood to the areas that need it most.
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