Dr. Frank Smith
Fishing for answers: Dr. Frank Smith looks to zebrafish to explain heart-nervous system interactions
Dr. Frank Smith is unique in beginning to use zebrafish to study how neurons function in the heart. “There are more than a million neurons in the human heart,” says Dr. Smith, an associate professor in Dalhousie Medical School’s Department of Anatomy & Neurobiology and a member of the Cardiovascular Research Group. “Of these, there are at least six different varieties, and they work differently than central nervous system neurons.”
The heart of the zebrafish is transparent and contains only a few hundred neurons. “This allows me to see the heart’s entire neural network… impossible in humans and in other mammals I’ve worked with,” Dr. Smith explains. “It’s a simpler system that provides a sketch of the role of the cardiac nervous system in controlling this organ and its interactions with the rest of the body. Amazingly, basic heart function works the same in all vertebrates – from fish to humans.”
The cardiac nervous system is part of the autonomic nervous system that runs independently of the brain to coordinate the beat-by-beat pumping of the heart. Dr. Smith has probed its complex nature and interactions with the rest of the nervous system and body for nearly 20 years.
“A number of nervous disorders affect the heart,” he notes. “Alzheimer’s Disease increases the risk of arrhythmia, for instance, while autonomic nervous dysfunction can narrow the arteries, raise blood pressure, and reduce oxygen levels in the heart. This contributes to ischemic injury, which can lead to heart failure or heart attack. At the same time, injury to the heart may affect the autonomic nervous system.”
Dr. Smith aims to unravel how cardiac neurons function in healthy hearts, and what happens to them as hearts become increasingly diseased. “There may be something about the most robust neurons that could be used to help strengthen the heart… or ways to stimulate the nervous system to improve the heart’s function,” he says.
Dr. Smith’s past work with Dalhousie colleagues has led to improved protection of the cardiac nervous system during surgery.