How brain cell activity alters blood flow in the brain is unclear, even though the phenomenon was first reported in 1890. Astrocytes are major support cells in the brain, that form enlarged, club-shaped endings called endfeet. These endfeet wrap around all blood vessels, giving them the opportunity to control blood vessel diameter. A recent discovery has shown that changes in calcium levels in the endfeet trigger dramatic constriction in blood vessels. Although nerve cells can initiate this process by signalling to the endfeet, prolonged nerve cell activity can also result in the blood vessels dilating to supply oxygen and other nutrients to the nerve cells. Dr. Grant Gordon is investigating how nerve cell activity counters the constriction caused by the astrocytes to increase the diameter of blood vessels. His goal is to determine whether signals from the nerve cells inhibit constriction, information which could lead to new drugs for people with impaired or damaged cerebral blood vessels, such as stroke patients.