What makes new mothers sense less fear in frightening conditions? Researchers have finally discovered.
They revealed how the brain speedily delivers the hormone oxytocin - which new mothers have in elevated levels, starting with childbirth - to where it's needed, freeing them to protect their young.
In a study done in rats, they found that oxytocin rushes to the brain region governing fear, called the amygdala, courtesy of special cells that act like a neurological expressway.
Further, when the researchers provoked these cells into sending oxytocin to the amygdala, it diminished the rats' fearful responses to being startled.
The findings "could have implications for autism, anxiety and fear disorders," Live Science quoted study researcher Ron Stoop, a psychiatric neuroscientist at the University of Lausanne in Switzerland, as saying.
The work may also spur scientists to look more closely at the brain's activity at moments when oxytocin levels are high, such as during childbirth and lactation, Stoop said.
Oxytocin is produced in the hypothalamus, a marble-size region at the bottom of the brain, and released into blood. But the hormone also somehow makes its way into the rest of the brain, including the amygdala - a fact that has long-puzzled scientists, because the blood-brain barrier blocks oxytocin in the blood from moving into the brain.
The study has been published in the February issue of the journal Neuron.