11/01/91
CONTACT: Stanford University News Service (650) 723-2558
STANFORD -- Stress may endanger brain cells, a Stanford University biologist has found in animals, but friendships and emotional supports may help ameliorate the danger.
Robert Sapolsky, a MacArthur Fellow and Presidential Young Investigator, studies stress; for the past dozen years, he's spent nine months out of the year in the laboratory, analyzing what stress hormones do to brain cells; three months each summer, following a troupe of olive baboons in the East African Serengeti, documenting the effect of such real-life stress as a fight with the boss.
The word from the lab is rather discouraging. Sapolsky has strong evidence from rats - though he's not at all sure about humans yet - that stress hormones can damage the hippocampus, the part of the brain involved in learning and memory.
The word from the field is more positive. Just as with humans, the right attitude - and even friends - can help.
Looking at the hippocampus in rats, Sapolsky has shown that the events that damage brain cells - stroke, seizure, aging - are more likely to kill those cells if stress hormones, or glucocorticoids, are present.
Sapolsky's research group was the first to show that in the hippocampus, glucocorticoids inhibit glucose transport in the neurons - disrupting energy storage in the cells. This leaves the nerve cell with less energy to combat events that cause a neuron to die.
"The hormones probably don't out-and-out kill the brain cells," Sapolsky said. "They seem instead to endanger them, take the brain cells and in effect put them on the edge of a cliff. If nothing else happens at that point, the neurons will recover from that period of stress just fine.
"On the other hand, if during that period you challenge the cells with too much work - for example, during a seizure - or challenge them with too little oxygen - for example, during a stroke - cells on the edge of the cliff are likely to be pushed over."
One reason for concern about these findings is that corticosteroids, such as hydrocortisone, are used by millions of people in drugs that treat ailments from skin rash to asthma and arthritis. Should these people worry about neurological side effects?
"We at least have to ask these questions," Sapolsky said. He emphasizes, however, that all the studies so far have been on rats or primates.
In the Serengeti, Sapolsky observes events in the daily lives of the baboons, then tranquilizes individuals and takes blood samples to record levels of stress hormones. For years, his research seemed to show that the least stressful role for a male baboon was to be the boss - the dominant male who dishes out, rather than receives, aggression. But with longer observation, he found that some dominant males had relatively high levels of stress hormones in their blood and some non-dominant baboons had low levels.
The difference, he found, was coping style. Baboons with low stress indicators included animals with strong enough personalities to control threatening events; those that could distinguish between a real threat and a false one; and, healthiest of all, those that turned to friends to comfort them after a threat.
"Baboons who have friends do much better in terms of their physiology," Sapolsky said. "And if that applies to a baboon, it could certainly apply for a human."
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