Mild stress leads to bromances between male rats, campus study says

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In times of distress, male rats, much like humans, enjoy snuggling and hanging out with each other, according to a recent study by campus researchers Elizabeth Kirby and Sandra Muroy.

The study discovered that mild stress actually makes male-to-male interactions more social and cooperative, allowing for greater social bonding and long-term benefits for mental health. The three year study began with a “serendipitous observation,” Kirby said.

“We were looking at how stress would lead to the improvement in rats’ memory functions,” Muroy said. “As we analyzed the data there was something going on in there with the cagemates and we started looking at the effects of stress.”

Studies have shown that when stressed, women reach out for social support. Little research, however, has been done regarding male-to-male relationships.

“For a long time we thought of males as more aggressive and competitive,” said UC Berkeley psychology professor Dacher Keltner. “Here is data showing that in the context of stress, we affiliate well.”

The experiment compared the effects of a mild stressor and a severe stressor with pairs of male rats that were “cagemates.”

“Rats, like humans, live in a network,” Kirby said. “They like having rat friends, just like people like having people friends.”

The mild stressor experiment consisted of immobilizing the rats — similar to confining a person in a small room — for three hours after two weeks of living together, Muroy said. Once the mild stressor ceased, rats returned to their old cage. After two weeks, rats were deprived of water for about 12 hours.

“When they went back home, they were much more social,” Kirby said. “The first thing they do is snuggle together and spend a lot of time laying down right next to each other.”

Once water was restored, the rats shared the water. Rats not subjected to the stressor, in contrast, became more aggressive drinking the water, with “pushing and shoving” that was unseen with the rats that went through the mild stressor, according to Muroy.

The experiment also studied the effects of severe stress by exposing rats to the same immobilization as they were during the mild stressor, but then also adding the odor of urine from a fox — a predator — inside the cages the rats returned to.

“They didn’t cuddle, they didn’t share the resources,” Muroy said. “There was more withdrawal and they were not interacting with their cagemate.”

During both experiments, the level of the hormone oxytocin — a chemical that supports social behavior, according to Keltner — changed. Rats that underwent the mild stressor had an increase in oxytocin levels, helping them become more trusting and generous, while rats that experienced the severe stressor had decreased oxytocin receptor levels in the brain, making them more isolated and withdrawn in their behavior.

The findings could benefit people experiencing trauma, and speaks to the importance of social support after a severely stressful situation.

“Stress is given a very bad reputation and we tend to not give importance to all these social relationships we do have,” Muroy said. “Some stress can be very beneficial if you think of it as a challenge that you can overcome through reaching out to your networks.”

Contact Sofia Gonzalez-Platas at [email protected] and follow her on Twitter at @sglezplatas.