First chemo brain & now potential radio brain:WBR & possible dementia

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"There is a growing concern about the cognitive consequences of whole-brain radiation," said Judy Brunso-Bechtold, PhD, a professor of neurobiology and anatomy and senior researcher. "Our findings suggest that very subtle changes may be critical and that glutamate receptors may be one of those changes."

The researchers focused on middle-age rats because middle-age adults are most prone to the cancers that require whole-brain irradiation treatment. Half of the rats received doses of whole-brain radiation similar to what humans receive. The other half received "sham" treatments that involved no radiation. One year later, researchers tested the rats' learning and memory using a water maze.

The rats that had received radiation performed significantly worse than the untreated animals. Additional experiments were conducted to determine if these deficits were associated with cell-to-cell communication in the hippocampus, a region of the brain associated with learning and memory.

The scientists specifically looked at glutamate receptors that lie on cell membranes. There are several different subtypes of the receptors that differ in the types of brain chemicals that most readily bind to them. They found that the composition of these subtypes was different in the animals receiving whole-brain irradiation.

"This shift in composition could impair synaptic communication and lead to the spatial learning and memory deficits measured in the treated rats," said Shi.

Next, the researchers will see if the chemical changes also extend to the synapses themselves. They also want to focus on why some animals – and people – experience cognitive deficits while others don't. Eventually, they hope to test drug therapies that may prevent the effects.

Shi received the 2006 Marie Curie Award from the Radiation Research Society for the research.

The research is supported by a recently funded grant from the National Institutes of Health and is part of a broad collaboration among researchers led by Michael Robbins, PhD, in the Department of Radiation Oncology. Other co-researchers were Michelle Adams, PhD, Michelle Nicolle, PhD, William Sonntag, PhD, and Kenneth Wheeler, PhD, all from Wake Forest.