Medical Professionals Reveal the Underlying Causes of Fainting Spells
In a groundbreaking study, researchers at the University of California San Diego have discovered a previously unknown connection between the heart and the brain that could potentially explain the causes of fainting. The findings, published in Nature, reveal a set of sensory neurons that link the heart directly to the brain, contradicting long-held beliefs about the body's relationship to the brain.
Assistant Professor Vineet Augustine and his team identified a genetic cardiac reflex in mice that mirrors human fainting in terms of physiology, behavior, and neural responses. This reflex suggests that our hearts may have more influence over our consciousness than previously thought.
The study found that the activation of these neurons – called NPY2R VSNs – caused rapid pupil dilation and eye rolls in mice, symptoms associated with human fainting. The researchers also observed that, while reduced blood flow to the brain was a factor, the brain itself may play a significant role in the process of fainting.
These neurons are part of the vagus nerve, which extends from the brain to various organs, including the heart. Using advanced techniques such as single-cell RNA sequencing and optogenetics, the researchers stimulated these neurons in mice, causing them to exhibit syncope-like symptoms.
Understanding these pathways could inspire novel treatment approaches for cardiac-related syncope, according to cardiologist Kalyanam Shivkumar from the University of California, Los Angeles. The researchers recorded the activity of thousands of neurons across different brain regions as the mice experienced induced fainting, revealing a decrease in brain activity in all areas except the periventricular zone of the hypothalamus.
The study's findings offer insights into the mechanisms behind fainting and promise to unravel long-standing cardiac enigmas. Clinical cardiologist Richard Sutton from Imperial College London has described it as a thrilling advancement with the potential to revolutionize our understanding of the complex interplay between the heart and the brain.
However, further research is needed to determine what exactly causes these neurons to fire and induce fainting. The significance of this inquiry lies with clinical neurologist Jan Gert van Dijk of Leiden University Medical Centre, who has pondered the nature of these neurons throughout his career.
In essence, the study reveals that a specific subset of vagal sensory neurons in the nodose ganglion, which respond to changes in cardiac output, blood pressure, or the release of specific peptides, becomes activated in response to signals from the heart. This activation sends signals to the brainstem and midbrain, resulting in bradycardia, hypotension, and loss of consciousness – the hallmarks of syncope. When these neurons are silenced, fainting is prevented.
The findings provide a neural explanation for how fainting is triggered, identifying precise cells and pathways that could pave the way for new therapies for conditions causing repeated fainting episodes.
The study in question has highlighted a set of sensory neurons, known as NPY2R VSNs, which are associated with fainting and are located within the vagus nerve, connecting the heart and brain. These findings could potentially influence health-and-wellness, mental-health, and medical-conditions by offering novel therapies-and-treatments for cardiac-related syncope.
This research opens up possibilities for understanding the complex interplay between the heart and the brain, specifically providing insights into the neural pathways that cause fainting, potentially leading to new treatments for individuals who experience repeated episodes of this condition.
