Stress can damage the brain. The hormones it releases can change the way nerves fire, and send circuits into a dangerous feedback loop, leaving us vulnerable to anxiety, depression and post-traumatic stress disorder.
But how stress accomplishes its sinister work on a cellular level has remained mysterious.
Neuroscientists at a University of California at Berkeley lab have uncovered evidence that a well-known stress hormone trips a switch in stem cells in the brain, causing them to produce a white matter cell that ultimately can change the way circuits are connected in the brain.
This key step toward hardening wires, the researchers found, may be at the heart of the hyper-connected circuits associated with prolonged, acute stress, according to the study published online Tuesday in the journal Molecular Psychiatry.
The findings strengthen an emerging view that cells once written off as little more than glue, insulation and scaffolding may regulate and reorganize the brain’s circuitry.
Researchers examined a population of stem cells in the brain’s hippocampus, an area critical to fusing emotion and memory, and one that has been known to shrink under the effects of prolonged acute stress. Under normal circumstances, these cells form new neurons or glia, a type of white matter.
But the stress hormone corticosterone (the rodent equivalent of cortisol in humans) can trip up that programming. Instead, the stem cells produce an abundance of oligodendrocytes, cells that help coat long fibers of neurons, known as axons, with a protective sheath. That sheath, made of myelin, is critical for the transmission of electrochemical signals that are the essence of our central nervous system.
“Usually the brain doesn’t make much oligodendrocytes in adulthood from those neural stem cells,” said UC Berkeley neuroscientist Daniela Kaufer, lead investigator of the study. In fact, a recent study suggested these cells were incapable of producing oligodendrocytes, which are somewhat like a vine spreading out and wrapping around axons, both insulating and supporting them.