Sleep apnea is common Accompanied by high blood pressurewhich contributes to the heart health risks associated with both diseases. Now scientists have identified two brain chemicals that play a role in this chain reaction and may pave the way for new treatments.
A lab rat study published in May found that Journal of PhysiologyThe scientists narrowed their focus to two chemicals produced in the brain that are known to affect blood pressure. OxytocinThey wanted to see how these two “neurohormones” — a hormone known to help with attachment and social bonding, and corticotropin-releasing hormone (CRH) — affect the brain stem, the lower part of the brain responsible for controlling many involuntary functions. blood pressure.
People with sleep apnea temporarily stop breathing while they sleep. sleepThe body is temporarily deprived of oxygen, resulting in hypoxia.
“When the body runs out of oxygen, a condition called hypoxia occurs, and the body’s reflex response is to breathe more to restore oxygen levels,” she says. Dr. David Klein“It also triggers a reflex to increase blood pressure to send oxygenated blood to where it’s needed,” Klein, a professor at the University of Missouri College of Veterinary Medicine who oversaw the study, told Live Science.
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However, although it is known that both oxytocin and CRH can alter blood pressure, the effects following these brief, repeated bouts of hypoxia were not fully understood.
The researchers conducted an experiment in which lab rats were split into two groups: one group was kept at normal oxygen levels, while the other group was subjected to intermittent hypoxia to mimic aspects of a sleep apnea attack.
The experiment lasted for 10 days, after which the scientists took samples from the rats’ brain stems and analyzed neuronal activity using a variety of techniques. They also took brain tissue samples and examined them under a microscope for oxytocin and CRH activity, as well as manually counting the number of specific brain cells that responded to the two chemicals.
Both oxytocin and CRH are produced by cells in a structure called the paraventricular nucleus (PVN). These PVN cells are connected to the main sensory centres in the brainstem and receive signals from the body that tell them how to regulate the cardiovascular system, including blood pressure. Oxytocin and CRH are involved in sending such signals, and experiments have shown that hypoxia intensifies their effects.
The two chemicals had a greater effect on brainstem activity in hypoxic rats than in rats kept with normal oxygen levels. After a period of hypoxia, the release of chemicals from the PVN increased, as did the number of receptors the chemicals bound to in the brainstem. This resulted in an increase in the number of signals emanating from the brainstem sensory centers.
Based on these findings, Klein said sleep apnea may exaggerate the effects of oxytocin and CRH on the brain stem, resulting in increased blood pressure.
In other words, when chemicals are released after hypoxia, blood pressure gets higher and higher each time, Klein said. When this happens often enough over a period of weeks, it causes changes in the areas of the brain that control blood pressure, so blood pressure stays high, he hypothesized.
However, this study did not specifically investigate the mechanism behind this, and the research group is currently working on studies that may shed light on these unknowns.
Klein said that if more chemicals involved in this mechanism are identified, specific drugs could be developed to target them and lower blood pressure in people with sleep apnea.
He noted that the effects of oxytocin and CRH vary depending on the areas of the brain they interact with, so a blanket drug that acts on the entire brain may not be the best option. actually Decreased blood pressure For example, they may target a different part of the brain stem than the one the team studied.
However, in the areas the researchers focused on, both chemicals had rather uplifting effects, Procopio Gama de Barcelos Filho“We found that the chromosomes in the chromosome 100 were not identifiable,” a postdoctoral researcher in Klein’s lab who led the study told Live Science.
“We think this basic research will open up new avenues that clinicians and pharmaceutical companies can use,” Klein said, but cautioned that there is still a long way to go before the findings can be translated into treatments for human patients.
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