The male prairie vole's interest in defending his pups, an oddity in male rodents, may come in part from his brain's production of a compound linked to aggressive behavior in mice, according to new results from researchers at The Johns Hopkins University.

Scientists found evidence suggesting that the male vole's brain chemistry more closely resembles nursing mouse females than it does his feckless male mouse counterparts, an intriguing possibility that could help researchers begin to tease apart some of the complex biochemical roots of mating-related behaviors.

"By focusing on these specialized behaviors, we're starting to pick up on some important similarities in the ways they may be triggered," says Stephen Gammie, a postdoctoral fellow in the Psychology Department at Hopkins. "When they and their pups are approached by a stranger, both the male vole and the female mouse with pups experience increased production of a compound called citrulline in the brain."

Citrulline is a byproduct of the reaction brain cells use to produce the messenger compound nitric oxide, which suggests that nitric oxide plays a role in turning on these forms of aggression.

Hopkins scientists began to investigate nitric oxide's relationship to aggressive behavior four years ago, when they found that a line of genetically engineered mice produced to study brain damage from stroke had suffered an unexpected side effect. The males among the mice were unusually aggressive, relentlessly attacking other males and ignoring female rejection of attempts to mate.

Researchers had given the mice a damaged form of the gene for a protein known as nitric oxide synthase, theoretically leaving the mice with little or no nitric oxide in their brains.

Earlier this year, researchers studied the effects of the modification on female mic
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Contact: Michael Purdy
mcp@jhu.edu
410-516-7160
Johns Hopkins University
25-Oct-1999