At that point, scientists in Dr. Julius’s lab knew that the receptor they had identified — TRPV1, a channel on the surface of cells activated by capsaicin — had to have evolved primarily for a more common stimulus, beyond the rare instances when someone might encounter hot peppers. That other stimulus turned out to be heat, said Dr. Michael Caterina, a professor of neurosurgery at the Johns Hopkins University School of Medicine who helped run a critical 1997 study on the topic in Dr. Julius’s lab. Acid activated the channel, too.

Tobias Rosen, an undergraduate in the lab, “came up with the clever recognition that essentially what we had cloned was a hot and sour soup receptor,” Dr. Caterina said. “It has acid, it has hot temperature, and it’s spicy.”

In search of the molecular basis for touch, Dr. Patapoutian, too, had to sift through a number of possible genes. One by one, he and his collaborators inactivated genes until they identified the single one that, when disabled, made the cells insensitive to the poke of a tiny pipette.

The channel integral to the sense of touch became known as Piezo1, after the Greek word for pressure. That channel and a similar one, both described in a 2010 paper, are now known to regulate a number of bodily functions that are sensitive to stretch, said Dr. Walter Koroshetz, the director of the N.I.H. National Institute on Neurological Disorders and Stroke, which provided funding to Dr. Julius’s and Dr. Patapoutian’s labs.

Those functions include the working of blood vessels, breathing and sensitivity to a full bladder.

The identification of pain receptors prompted a flurry of interest from pharmaceutical companies: If you could block the channel identified by Dr. Julius, they reasoned, you could address chronic pain.

But there were several major problems. One is that some sensitivity to pain is useful; without it, people risk running a scalding hot bath or burning their hands on a stovetop. “Pain serves a purpose,” Dr. Caterina said.

Another is that the same channels responsive to heat also turned out to contribute to the control of body temperature. Blocking them was found to cause a slight fever — a potentially major liability.

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