New culprit for high blood pressure discovered

High blood pressure has just gotten a new culprit: a newly discovered brain cell.

While the usual suspects of heart risk — weight problems, stress, smoking, those salty slices of bacon — do contribute to high blood pressure, researchers think they've discovered a new cluster of neurons that also play a role.

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Researchers from Sweden spotted the previously unknown cluster of nerve cells in the brains of mice, finding the cells affected the animals' blood pressure and other cardiovascular functions. If these neurons also exist in human brains, scientists and doctors may have a new avenue for tackling hypertension (chronically high blood pressure) and other heart problems.

These cells, which are part of a family of nerves known as parvalbuminergic neurons, are located in the hypothalamus of the mouse brain, a region that helps control involuntary functions such as thirst, body temperature and blood pressure.

Jens Mittag, a molecular biologist at Sweden's Karolinska Institutet, and his team focused on mice that had mutations in a cell receptor for thyroid hormone. This defect prevented their hearts from responding normally to stressful stimuli, such as environmental temperature changes. [10 Odd Facts About the Brain]

Thyroid hormone problems have been known to affect the heart directly in humans. To determine whether the hypothalamus also played a role, Mittag and his team scanned the brains of the mutated mice, finding the hypothalamus was missing a significant number of parvalbuminergic neurons.

Here's what the researchers think is happening: The thyroid hormone, produced by the thyroid gland in the brain in the neck, is partly responsible for making these special neurons. Mice with a lack of thyroid hormone activity didn't successfully form these parvalbuminergic neurons during embryonic development.

The researchers confirmed the role of these neurons in another experiment in which they destroyed these cells in other mice with the help of a virus. This action led to hypertension and heart-rate problems in the presence of temperature changes.

"There's lots of anatomical areas in the brain that we know regulate the control of cardiovascular function. These are the first neurons in the hypothalamus on the cellular level that we know regulate these parameters," Mittag told LiveScience.

"I have no idea why no one has stumbled over these cells before," he added. "I guess we were lucky to be the first to describe them."

Before scientists can think about targeting these neurons for hypertension treatment in humans, further studies are needed to confirm that these cells are present in human brains and perform the same jobs.

In the meantime, Mittag said the study underscores the importance of making sure that pregnant women produce a sufficient amount of thyroid hormone. Without it, the brain of the fetus may not develop properly and, according to this study, cardiovascular issues from a lack of parvalbuminergic neurons may be just one more problem for the fetus that can be caused by insufficient thyroid hormone production in the mother.

The research was detailed online Dec. 21 in the Journal of Clinical Investigation.

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