By Yehudis Kundin, Staff Writer
We often take for granted the constant, steady flow of blood through our veins and arteries that keeps us functioning every second of our lives. This process is regulated by the autonomic nervous system, a network of nerves throughout the body that controls unconscious processes. This allows us to go about our daily lives without constantly having to command our bodies to breathe and pump our blood. However, proper blood flow is not always a given.
High blood pressure, or hypertension, occurs as a result of the tightening of small arteries called arterioles, which regulate the flow of blood through the body. As a result of this constriction, the heart must work harder to pump blood through these smaller spaces, increasing blood pressure (the force of the blood on the walls of arteries). This can be beneficial in fight-or-flight situations. Blood vessels leading to non-essential areas, such as the digestive system, are constricted to direct blood flow to essential areas, such as the muscles and the brain. After the perceived threat passes, the blood vessels return to normal.
However, chronic hypertension can be extremely dangerous. With decreased spaces within arteries, blood clots can stop the flow of blood to the brain or heart and cause strokes and heart attacks. Hypertension can also lead to other cardiovascular diseases, such as coronary artery disease and heart failure. It is an unfortunately common condition, with 47.7% of adults worldwide having hypertension between August 2021-August 2023. This is a significant number that can’t be ignored.
Many medications have been introduced over the years to treat hypertension. Alpha blockers such as Doxazosin and Prazosin prevent the hormone norepinephrine from constricting smaller arteries and veins. Renin inhibitors, such as Aliskiren, inhibit renin, a substance produced by the kidneys that raises blood pressure. However, there are many common side effects to these medications, such as dizziness and upset stomach. Additionally, these medications treat symptoms but don’t actually address the cause.
Scientists at the University of São Paulo in Brazil and the University of Auckland in New Zealand may have found just that, as well as a potential way to combat it.
Their findings suggest that the lateral parafacial (pFL) brain region can trigger biological changes that result in high blood pressure. The pFL neurons play a crucial role in breathing control. It’s what causes those forceful exhalations we experience during intense exercise or just simply coughing. However, tests on rats revealed that pFL has another job: constricting blood vessels. This mechanism is physiologically advantageous during exercise, as it redirects blood flow to vital organs like the heart. Conversely, this same pathway may also drive the pathological vessel tightening observed in hypertension. They suggest that upon detecting even slight breathing changes, pFL neurons can activate the sympathetic nervous system (the “fight-or-flight response”) that then controls blood pressure, constricting some blood vessels to direct the flow of blood to the places it deems essential for the task at hand. Chronic blood vessel constriction results despite the absence of any threats in the environment. Using genetic engineering techniques to control the activation of pFL neurons, the scientists experimented by activating pFL neurons in hypertensive rats and found that it resulted in an increase in blood pressure. When they mapped out the neuron activity, they found that the pFL neurons were acting to constrict blood vessels in addition to controlling breathing. When they inactivated these neurons, the blood pressure of the rats returned to normal. Their research exposed a direct link between the nervous system and blood pressure that can be crucial in finding a direct intervention to cure the root cause of hypertension.
Targeting the pFL neurons is the researchers’ next step, and they have already identified a possible mechanism by which to keep these neurons in check. Clusters of cells known as carotid bodies found in the neck act like tiny sensors that can influence pFL neuron activity from outside the brain. Their goal is to create a drug that can inactivate these sensors to decrease pFL activity safely, without having to penetrate the brain. More research is needed to synthesize these drugs and test them on animal models before moving to humans, but the discovery of the role of pFL neurons in hypertension is a big step forward in neuro-cardiovascular research that can contribute to a widespread decrease in this fatal disease.
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