Tiny Amounts of Neurotransmitter Offer Big Clues to Women’s Hypertension
Research took a step toward understanding hypertension in women by using a new technique to examine the release of a neurotransmitter in small blood vessels.
After menopause, women have an increased risk of hypertension, and among older adults, more women than men have hypertension. Yet, research in hypertension has focused on males, and little is known about how women’s bodies manage blood flow.
“The answer to why women have more problem with hypertension seems to be in the synapse,” said exercise scientist Heidi Kluess.
The synapse is the space between the nerve and the vascular smooth muscle, the place where the nerve and blood vessel interact. A neurotransmitter crosses the synapse to activate a receptor, which then causes the artery to constrict.
“There’s been a little evidence to say that some of the neurotransmitter breakdown is different in women. It suggests that when we’ve been looking at receptors on the smooth muscle, we may have been missing a big part of the story, particularly in women,” Kluess said. “That’s where I started from.”
Kluess measured the neurotransmitter adenosine triphosphate (ATP) coming from the small blood vessels known as arterioles. ATP plays a key role in controlling blood flow and blood pressure by causing the diameter of blood vessels to change. Thus, the constriction of veins associated with hypertension could be related to relatively high levels of ATP in arterioles.
Kluess’ first set of questions were aimed at understanding where the ATP comes from, what tissues are releasing it and how this changes with aging.
The researchers found that ATP is released mostly from the sympathetic nerves in the arteriole wall and that only a small part comes from the smooth muscle.
They also found that the ATP overflow varied considerably with age. Because ATP is associated with vascular growth, it is important during early development when blood vessels are growing, but levels generally decline when people reach their twenties. Elevated levels can be a bad sign during aging and may be a predictor of vascular changes that can be detected years before hypertension is a problem.