Frequent sleep apnea it comes with high blood pressure, which, in turn, contributes to the cardiovascular risks associated with both conditions. Now, scientists have identified two brain chemicals that play this role and could pave the way for new treatments.
In a study of lab rats published in May Journal of PhysiologyThe scientists looked at two chemicals in the brain known to affect blood pressure: oxytocin, also famous for its social networking features, and corticotropin-releasing hormone (CRH). They wanted to see how these two “neurohormones” affect the “brainstem”, which is a structure below the brain tasked with controlling many voluntary functions, including. blood pressure.
People with sleep apnea stop breathing for a while go to sleep, temporarily depriving the body of oxygen. This puts it in a hypoxic, or low-oxygen, environment.
“When the body decreases oxygen, a condition called hypoxia, this makes us want to increase our breathing which will restore our oxygen level,” he said. Dr. David Kline, a professor at the University of Missouri College of Veterinary Medicine who oversaw the study. “It also causes our blood pressure to go up to get the oxygenated blood to where it needs to go,” Kline told Live Science.
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However, although it is known that oxytocin and CRH can modulate blood pressure, their effects after short-term, repeated bursts of hypoxia were not fully understood.
The researchers conducted their experiments with laboratory rats that were divided into two groups: One group was kept in normal oxygen conditions, while the second group was placed occasionally under low oxygen levels to mimic episodes of sleep apnea.
The experiment lasted 10 days, after which the scientists collected samples of the rats’ brains to examine the activity of their nerves using different methods. Some brain tissue samples were taken to examine the activity of oxytocin and CRH using a microscope, and the number of specific brain cells that responded to the two chemicals was done manually.
Both oxytocin and CRH are made by cells in a structure called the paraventricular nucleus (PVN). These PVN cells feed into the main sensory center in the brain that receives signals from the body that dictate how to control the cardiovascular system, including blood pressure. Oxytocin and CRH have a hand in sending such signals – but experiments have shown that hypoxia enhances their influence.
The two chemicals had a greater effect on the brain activity of hypoxic rats than rats kept in normal oxygen conditions. After the reduction in oxygen levels, there was an increase in the release of chemicals from the PVN, as well as an increase in the number of receptors they activate in the brain. of the brain. On the other hand, there was an increase in the number of signals sent by the sensory center of the brain.
Based on these findings, Kline said sleep apnea may exacerbate the effects of oxytocin and CRH in the brain, which may result in increased blood pressure.
In other words, the release of chemicals after hypoxic events causes blood pressure to be higher and higher over time, Kline said. As the weeks go by, if this happens repeatedly, the blood pressure stays high because the areas of the brain responsible for controlling the blood pressure are changed, he thought.
However, this study did not specifically look at the mechanisms behind this; the team is already working on studies that may clarify these unknowns.
After many of the chemicals involved in the mechanism are identified, specific drugs can be developed to target them and reduce blood pressure in patients with sleep disorders, Kline said.
Drugs that affect the entire brain may not be the best choice, he noted, because the effects of oxytocin and CRH depend on which areas of the brain they interact with. Both chemicals indeed decrease blood pressure if they target different parts of the brain than the group studied, e.g.
However, in the area where the researchers focused, both chemicals had a high effect, Procopio Gama de Barcellos Filhoa postdoctoral researcher in Kline’s laboratory who led the study, told Live Science.
“I think all of this basic research will lead us to new approaches that can be taken by doctors and drug companies,” Kline said. However, he warned that there is still a long way to go to integrate their findings into a treatment for human patients.
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