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Science agrees: Moms courageous, cool

Findings from rat experiment may apply to humans, too

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WASHINGTON (Reuters) -- It may not feel like it for a woman struggling to get her kids off to school just as the microwave explodes and the car gets a flat tire, but females with children are calmer under pressure and deal with adversity better, a U.S. researcher said on Tuesday.

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Neuroscientist Craig Kinsley of the University of Richmond does his work with rats, but he said his findings probably apply to other animals and humans as well.

Kinsley found that female rats that have had one or more litters are much less stressed out when provoked than rats without pups. When he examined their brains, he found much less activity in the fear centers of the brains of mother rats.

Writing in the journal Physiology and Behavior, he called the phenomenon "maternal induced neural plasticity."

In 1999, Kinsley published research showing that pregnancy hormones seemed to nurture brain cells involved in learning and memory. Mother rats did better than their virgin sisters in a rat maze test.

In the new study, Kinsley found that mother rats are not only smarter, but calmer and braver.

"There's something about pregnancy and subsequent exposure to offspring that create a more adaptive brain, one that's generally less susceptible to fear and stress," he said in a statement.

In their most recent research, Kinsley and colleagues stressed the rats by putting them into what they called a "restraint tube" -- a clear Plexiglas tube -- which they then put into a bright room.

"Rats don't like being restrained and they don't like light," said Kinsley, who is chairman of the psychology department. "This task then makes them highly agitated."

They also put the rats into an open space.

"Again, rodents like dark, covered areas; they don't like open and lighted spaces," Kinsley said. "They tend to hug the walls and move sparingly. They don't move around much because such movement may attract the attention of a variety of potential predators."

Females that had never had a litter tended to freeze up and move haltingly, while the mother rats explored.

"When we examined these animals' brains, the regions that regulate fear, (such as the) amygdala, showed less activation. Overall, they were much less fearful," Kinsley said.

Kinsley said other studies he had done suggested the changes are permanent. "The effects also appear to last for a lifetime," he said.

Mother animals are notoriously fierce, so the findings are not unexpected, Kinsley said.

"From the female's standpoint, if she's too frightened to fend off predators or other threats to her offspring, she cannot protect her offspring," he said.

"The mother will do what it takes to get the job done, and done well and efficiently."

The findings almost certainly apply to humans, he said. People share most of their genes with rats and such basic behaviors are very likely to be similar among mammals and probably other species, too.

Copyright 2003 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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