This Is Why You Feel Pain

When you're in severe pain, it swallows up your entire world. But the neurological process of feeling pain comes down to just a few neurochemical pathways. Now, scientists are unraveling the mystery of the chemistry underlying our "pain sensor," and one day this could ease our suffering.

Over on Quanta, Emily Singer has a terrific story about the discovery of our pain circuits. It begins like this:

The fiery sting of a habanero pepper, the scalding heat of a boiling teapot, the excruciating bite of the earth tiger tarantula, and even the heightened sensitivity to touch following a sunburn — all of these painful sensations are made possible by a sophisticated molecular machine operating in nerve fibers in the skin and tongue.

Known as TRPV1, the protein was discovered more than 15 years ago. Although scientists knew that it could sense heat and various chemicals, exactly how it worked remained a mystery.

In December, however, scientists reported creating a high-resolution image of the protein's structure for the first time. Like the blueprint of a motor, that information should help researchers understand how the tiny apparatus can respond to such a wide array of signals — from temperature to toxins — and the role it plays in both acute and chronic pain. The results could ultimately lead to new painkillers, potentially without the troublesome side effects of opiates.

David Julius began hunting for TRPV1 close to 20 years ago. At the time, scientists had for decades been using capsaicin, the molecule that gives chili peppers their heat, to study pain. But little was known about how it triggered that sensation. Other scientists had already tried and failed to find the molecule that binds to capsaicin, known as its receptor, but that only enticed Julius to take on the challenge. "People had looked for it for many years, and it took on a mythical glow," said Julius, a biologist at the University of California, San Francisco. "What is this elusive thing?"

He and his team reported hitting the jackpot in 1997, identifying a member of a family of receptors known as TRP (transient receptor potential) ion channels, which had been little studied in mammals. "They were kind of enigmatic," said Julius, whose office at UCSF is scattered with capsaicin-themed gifts like chili pepper neckties. His lab has since pioneered the study of TRPV1 and some of its cousins, which can detect cold as well as natural products such as menthol, garlic and wasabi.

Read the whole story at Quanta