San Francisco Veterans Administration Medical Center researchers said the findings were surprising and might be of clinical significance for the treatment of diabetics in hypoglycemic coma. But they caution the results, obtained in a rodent study, cannot be immediately extrapolated to humans.

Insulin is a hormone that moves glucose from the bloodstream to individual cells, where it is broken down and used for energy. Diabetics do not produce enough of their own insulin and must take it several times a day.

A severe insulin overdose can reduce levels of glucose in the blood to extremely low levels -- a condition known as hypoglycemia -- and cause hypoglycemic coma, resulting in destruction of neurons in the hippocampus and cerebral cortex, which are essential to memory and cognition.

"This study tells us for the first time that, in rats, the brain damage occurs not during the coma, but after it, when we give them glucose and their blood glucose levels return to normal," said principal investigator Dr. Raymond Swanson.

The study appears in the Journal of Clinical Investigation.