Heart-brain link offers new potential explanation for fainting

Fainting, a temporary loss of consciousness, affects almost 40% of people, yet scientists and physicians don’t know exactly why it happens. A drop in heart rate, blood pressure, and breathing rate—a trio of symptoms long known as the Bezold-Jarisch reflex—can contribute to fainting, researchers have hypothesized. Now, neuroscientists have pinpointed a nerve pathway between the heart and brain that triggers the reflex and can prompt fainting in mice. The findings prove the once-debated reflex exists, and they could one day point toward treatments for fainting in humans. The study is “an elegant tour de force,” says Robert Sheldon, a cardiologist and expert in fainting spells at the University of Calgary who was not involved in the work. But others caution that the reflex—and, hence, the newly discovered neural pathway—are not the whole story on fainting in humans, for whom scientists have a more detailed model that involves the sympathetic nervous system. “The experiments are correct,” says David Goldstein, an expert on the autonomic nervous system at the National Institute of Neurological Disorders and Stroke. “The inferences drawn about [fainting in humans] are incorrect.” For those who suffer from fainting, the condition can be scary and bewildering. Many ask, “Why me? Why now?” Sheldon says. To gain further insight, Vineet Augustine, a neuroscientist at the University of California, San Diego (UCSD), and colleagues examined different t...
Source: ScienceNOW - Category: Science Source Type: news