Protein 'switch' in brain controls blood flow: study

A protein "switch" within the tiny wire-like capillaries of the brain controls the blood flow that ensures optimal brain function, a new study has found.
Researchers from University of Vermont in the US have 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.
"When there is an increase in brain activity, there is an increase in blood flow," said Thomas Longden, assistant professor at the University of Vermont.
"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," Longden said.

Neurons consume an enormous amount of the body's energy supplies - about 20 per cent - yet lack their own reserves, so are reliant on blood to deliver nutrients, researchers said.
Previously, capillaries were thought to be passive tubes and the arterioles were thought to be the source of action.

Researchers 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.
To achieve this feat, the capillary sensory network relies on a protein (an ion channel) that detects increases in potassium during neuronal activity.

Increased activity of this channel facilitates the flow of ions across the capillary membrane, thereby creating a small electrical current that generates a negative charge - a rapidly transmitted signal - that communicates the need for additional blood flow to the upstream arterioles, which then results in increased blood flow to the capillaries, researchers said.
Researchers also determined that if the potassium level is too high, this mechanism can be disabled, which may contribute to blood flow disturbances in a broad range of brain disorders.
"These findings open new avenues in the way we can investigate cerebral diseases with a vascular component," said Fabrice Dabertrand of University of Vermont.

These findings were published in the journal Nature Neuroscience.