They detected 5,000 calcium signals per second in the capillaries in the tiny section of brain visible through the window, which they say amounts to about 1,000,000 of these responses each second in the entire brain's blood vessel system. When the cells lining the blood vessels received an influx of calcium, they glowed green.
BLOOD VESSELS IN THE BRAIN WINDOWS
The researchers then looked through little windows in the brains of these mice to investigate calcium's role in controlling blood flow in the brain's capillaries. Due to the efforts of Michael Kotlikoff's team at Cornell University, they were able to turn this tool on in the cells lining blood vessels of mice. Longden and his collaborators used a protein which emits green light when calcium increases in the cell. "The first electrical mechanism is like a crude sledgehammer approach to get more blood to the general vicinity of the increased brain activity by controlling the medium-sized arterioles, and then capillary calcium signals ensure exquisite fine-tuning to make sure the blood gets to exactly the right place at the right time through the tiny capillaries."ĭr. "There seem to be two mechanisms working in tandem to ensure that energy in the form of blood makes it to specific regions of the brain: one broad and the other precise," says Thomas Longden, Ph.D., Assistant Professor of Physiology at University of Maryland School of Medicine. For this latest paper, the team wanted to study the fine-tuning of blood as it flows through the capillaries to precisely regulate energy supply to tiny regions in the brain. In a 2017 Nature Neuroscience paper, the researchers showed that electrical pulses coursing through the capillaries direct blood flow from the medium-sized arterioles supplying large regions of the brain. Large arteries feed medium-sized vessels known as arterioles that then feed even tinier capillaries - so small that only a single blood cell can pass through at once. If the brain does not get blood to where it needs it when it needs it, the neurons become stressed, and over time they deteriorate ultimately leading to cognitive decline and memory problems. In their new paper, published on July 21 in Science Advances, the researchers say that understanding how the brain directs energy to itself in intricate detail can help determine what goes wrong in conditions like Alzheimer's disease and dementia, where faulty blood flow is a predictor for cognitive impairment. Now, University of Maryland School of Medicine and University of Vermont researchers have shown how the brain communicates to blood vessels when in need of energy, and how these blood vessels respond by relaxing or constricting to direct blood flow to specific brain regions.