“Whenever I get gloomy with the state of the world, I think about the arrivals gate at Heathrow Airport. … Fathers and sons, mothers and daughters, husbands and wives, boyfriends, girlfriends, old friends. … If you look for it, I’ve got a sneaky feeling you’ll find that love actually is all around.”—David, the Prime Minister, “Love Actually”
A hug causes the brain to release neurotransmitters and evokes feelings of trust and calm. But how exactly does your brain detect and know you are being hugged? It’s not with your eyes, but with tiny receptors found on the skin called mechanotransducers. These receptors—called Piezo receptors—were the body of work that won the 2021 Nobel Prize in Medicine or Physiology.
Aptly named, “piezo” is the Greek root for pressure or push and was largely characterized and discovered by Ardem Patapoutian, PhD, who was awarded the Nobel Prize in Medicine or Physiology. Drugs that block or activate the Piezo receptors have fun names such as Yoda1 or Dooku1, an ode to a popular movie franchise’s catchphrase “May the force be with you.”
These receptors are responsible for a wide variety of force detection, some of which science is still discovering. When these receptors are activated by force, pressure, touch or stretch, it causes a change in the shape of the Piezo receptor. When the shape of the receptor changes, it allows charged particles (ions) to pass through and activate neurons, which result in relaying a physiological message to other areas (like telling your brain that you’re being hugged).
Piezo receptors are found anywhere in the body where you would expect pressure or force to be sensed and in some unexpected places as well. They’re responsible for touch sensation and your body’s awareness of location and movement (proprioception). Piezo receptors are also the reason why scratching an itch feels satisfying. They also send a message from the bladder to the brain when it is stretched from being too full, saying it’s time to use the bathroom.
Research suggests that Piezo receptors are the primary receptor responsible for the baroreflex detection of blood pressure—a subject close to my own personal interests. The baroreflex is the primary way the body regulates blood pressure. Think of it as a blood pressure thermostat that’s kept at the ideal temperature (or pressure). If the thermostat is malfunctioning, it can cause large swings in blood pressure, which could bring about feelings of lightheadedness or fainting. Although strong data support the Piezo receptors for blood pressure detection, some scientists think more research to understand their importance is needed.
Whether it’s the feeling of a hug, having to use the bathroom or keeping your blood pressure regulated without you even noticing, you can thank the Piezo receptors and of course, Patapoutian and colleagues for their discovery.
Dain Jacob is a PhD student at the University of Missouri in the Nutrition and Exercise Physiology Department. His research focuses on autonomic regulation of the peripheral vasculature and the impact of environmental stressors and sex hormones.