THURSDAY, Dec. 20 (HealthDay News) -- Scientists are getting
warmer in their attempts to zero in on what causes hot flashes,
intense surges of heat and sweating that affect millions of
middle-aged women in the years leading to menopause.
Studying rats, researchers at the University of Arizona College
of Medicine, in Tucson, have pinpointed a small region of the brain
that may go awry during typical hot flashes, finding that a certain
set of neurons acts as a virtual control switch for the problem
when estrogen levels drop.
"I think the idea is to develop some alternate treatments for hot flashes, but how could we possibly develop appropriate treatments if we don't know what causes them?" said study author Dr. Naomi Rance, a neuropathologist, professor and associate head of pathology at the university. "This is the first evidence these neurons have anything to do with [heat] regulation."
Scientists note, however, that research with animals often fails
to provide similar results in humans.
The study appeared recently in the journal
Proceedings of the National Academy of Sciences.
An estimated 70 percent of women -- along with some men --
experience hot flashes, and previous research indicated the flashes
originated in the hypothalamus, a section of the brain serving as
the "switchboard" between hormone signals and the central nervous
University of Pittsburgh scientists published a study earlier
this year showing that the parasympathetic nervous system -- part
of the autonomic nervous system, which regulates unconscious bodily
functions such as heart rate and breathing -- isn't working as
efficiently as normal during a hot flash.
In the new research, Rance and her colleagues created an animal
model of menopause by using a toxin to deactivate a group of brain
cells known as KNDy (pronounced "candy") neurons in rats. After
these neurons were deactivated, the rats' tail skin temperature
consistently lowered, suggesting that the neurons control the
widening of the blood vessels known as vasodilation that lead to
hot flashes by increasing blood flow to the skin. The rats' tail
skin temperature rose after removal of their ovaries, which produce
"Hot flashes are really episodic vasodilation," Rance explained. "You can see it -- that's why people get red, because blood rises to the surface of the skin. Flushing is the body trying to get rid of that heat. Their core temperature is normal, so it doesn't make sense at all."
Current treatment for hot flashes includes estrogen replacement
therapy, which is controversial because of potential health risks,
including higher odds of certain cancers. Another option is
selective serotonin reuptake inhibitors (SSRIs), which are
traditionally used to treat depression.
Although the current research helps identify the basic biologic
mechanism behind hot flashes, it may be years before scientists are
able to develop new choices for treating them, Rance said.
Dr. Jill Rabin, chief of ambulatory care and obstetrics and
gynecology at Long Island Jewish Medical Center in New Hyde Park,
N.Y., praised Rance's study as "groundbreaking and very well
"The study is done in rats, so it's really hard to [translate the results] into people, but it's very, very interesting," said Rabin, who also is head of urogynecology. "This issue has been looked at for a long time and this may open the way, possibly, for a study in humans."
The National Women's Health Network offers more information
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