Brain researcher Brian MacVicar - photo by Martin Dee

UBC Reports | Vol. 52 | No. 3 | Mar. 2, 2006

Researchers Study Blood Flow in Brain

Insights might help prevent damage from clots or constriction

By Hilary Thomson

New insight into restoring blood flow in stroke and vascular dementia patients, and in newborns with asphyxia, is the goal of a collaborative study between UBC researchers and colleagues at the University of Helsinki, Finland.

Brian MacVicar, Canada Research Chair in Neuroscience, and Kai Kaila of the University of Helsinki, will work together on a two-year project, funded by a grant of almost $330,000 from the Academy of Finland, and from the Institute of Neurosciences, Mental Health and Addiction of the Canadian Institutes of Health Research.

“We want to understand the basic mechanics of how blood flow relates to brain activity,” says MacVicar, who is a professor in the Dept. of Psychiatry and a member of the Brain Research Centre at UBC Hospital. “It’s an area that’s still not understood despite its high impact for both basic and applied neuroscience.”

The brain has high energy demands. The organ represents only about two per cent of body weight, but accounts for up to 20 per cent of the body’s energy when at rest.

Blood flow supplies energy for brain activities, and the brain’s blood vessel contraction and dilation -- with resulting increase or decrease in blood flow -- is a normal part of brain functioning.

However, improperly regulated flow can result in brain disorder or damage. The interruption of blood flow due to a clot or blood vessel constriction (ischemic stroke) or the rupture of blood vessels (hemorrhagic stroke) causes brain cells in the affected area to die. Vascular dementia can develop when arteries feeding the brain become narrowed or blocked.

MacVicar says understanding of brain blood flow has advanced significantly in the past decade.

“We didn’t know all the players 10 years ago, nor did we understand the machinery,” he says. “Now we’re finally getting answers to the hundred-year-old question of how brain cell activity relates to blood flow and how the ‘control dial’ works.”

MacVicar is an expert in how astrocytes -- star-shaped cells that surround nerve cells and blood vessels in the brain -- regulate blood flow within the brain. In research published in Nature in 2004, MacVicar and post-doctoral fellow Sean Mulligan found that a calcium signal to astrocytes created constriction in vessels resulting in decreased brain blood flow.

Now MacVicar wonders if astrocytes also have a role in increasing blood flow. He will study the interplay between synaptic activity -- information flowing from one brain cell to another -- and astrocytes in regulating vascular tone and blood flow in the brain.

“If astrocytes prove to be triggers that dictate flow, we may be able to modify the signals and control the flow to prevent brain damage and loss of function, ” he says.

At the University of Helsinki, Kaila’s lab focuses on molecular and biophysical mechanisms related to synaptic activity. Kaila, and fellow lab member Juha Voipio, have identified a mechanism of brain cell-to-astrocyte communication that generates carbon dioxide -- a chemical signal known to have a profound effect on cerebral blood flow.

“The brain is often viewed as an information-processing machine only,” says Kaila. “A close look at its energy metabolism, however, reveals complexities of organization, trade-offs and optimizations. Understanding the control of regional blood flow will help us better understand brain diseases and hopefully help in the design of new therapies.”

Research findings will also aid in the treatment of newborns experiencing asphyxia, or insufficient intake of oxygen, a condition known as hypoxic-ischemic encephalopathy. Symptoms are similar to stroke in adults, and can result in permanent damage such as mental retardation and epilepsy. The condition affects two to four babies per 1,000 births in developed countries.

In addition, more information about brain blood flow mechanics will benefit brain imaging that looks at increased blood flow to determine areas of increased brain function or damage, says MacVicar, who is also a member of the Vancouver Coastal Health Research Institute.

Every year, 50,000 Canadians suffer a stroke. Another 300,000 people are living with the consequences of stroke, which is the leading cause of adult disability in Canada.

Vascular dementia is the second most common form of dementia after Alzheimer’s disease. One in 13 Canadians over age 65 is affected by Alzheimer’s disease and related dementias.

The Brain Research Centre comprises more than 150 investigators with multidisciplinary expertise in neuroscience research ranging from the test tube, to the bedside, to industrial spin-offs. The centre is a partnership of UBC and Vancouver Coastal Health Research Institute, the research body of the health authority.