A University of Vermont study suggests that the astrocytic BK channel is an important participant in the cellular process responsible for signaling regional blood flow changes in the brain, providing a new key to understanding such disorders as stroke, migraine and Alzheimer’s disease.
To function properly, the brain needs to receive an uninterrupted supply of oxygen and glucose, which is provided through an intricate network of blood vessels in the brain. Different parts of the brain are engaged by every activity, such as analytical thought, piano playing, seeing, hearing, walking, and these regions then require a rapid elevation of blood flow to meet the increased metabolic needs of the relevant brain cells (neurons). Though this cellular activity can be visualized in modern-day functional brain scans, the mechanisms by which these neurons signal blood vessels to dilate and increasing blood flow remain largely unknown, and are central to understanding brain function.
The diameter of blood vessels in the brain can be modulated by extracellular potassium, a common element present inside and outside all cells of the body. Such modulation of vessel diameter permits changes in blood flow to occur in the brain, as well as in other organs and tissues. With this knowledge, lead study author Mark Nelson, Ph.D., professor and chair of pharmacology at the University of Vermont, set out to determine whether the diameter of cerebral blood vessels in the brain could be modulated under physiological conditions by external potassium ions. To accomplish this, he and his research team studied the communication that takes place between neurons and blood vessels in mouse and rat brains.
The research team discovered early on that neuronal activity appeared to be communicated to the blood vessels through intermediary cells known as astrocytes. Astrocytes, which comprise about half the brain, had not been thought to play an active role in brain processes, and were thought to serve as the “glue” of the brain. One end of an individual astrocyte forms extensive contacts with thousands of neurons, while the other end surrounds and encases blood vessels. In this way, astrocytes are capable of integrating information from a large number of neurons and translating this information into distinct physiological outcomes, including modulation of blood flow.
This study suggests that these proteins may be novel targets to protect the brain from cerebrovascular disorders.