What Makes Male Mice Mellow Does Opposite to Females, Study Finds

From the Males are from Mars, Females are from Venus files: A chemical messenger in the brain that makes males mellow out has exactly the opposite effect in females, according to mouse studies from Johns Hopkins University. The compound is a neurotransmitter called nitric oxide.

Psychologist Stephen Gammie and his colleagues produced transgenic mice that have a defective system for producing nitric oxide. They previously reported that male mice lacking the neurotransmitter were extremely aggressive. They report in Wednesday’s Journal of Neuroscience, however, that females lacking the neurotransmitter become more docile, even to the point of failing to defend their pups in the presence of foreign males. The team is now trying to unertand why the chemical causes such different reactions in the two sexes.

Compiled by Times medical writer Thomas H. Maugh II