A new combination of ingredients extracted from the chili pepper promises to revolutionize anesthesia, by “attacking” only pain-sensing neurons in the nervous system and leaving other neurons unaffected.

Classic anesthesia is usually characterized by risks involving the amount of administrated anesthetic and by the familiar dizziness that accompanies the “awakening”. Scientists hope to eliminate the side effects using a combination of capsaicin (extracted from the chili pepper and which gives the vegetable its particular spice) and QX-314, a derivative of lidocaine (a local anesthetic used by dentists and to relieve inflamed, itchy skin).

The concoction effectively “neutralizes” the nerves responsible for sending the pain-related signals to the brain, but has no effect on other nerves responsible for motor functions and other sensations.

The idea is to have the QX-314 introduced inside the nerve cell since the compound is able to reduce the activity of the pain-sensing nerves only “from the inside”. However this is not an easy task, but physiology professor David Julius, from the University of California, noticed that the capsaicin has a selective “affection” for a protein known as TRPV, found in the membranes of pain-sensing neurons.

When capsaicin binds to TRPV1, it causes the protein to open a gate leading to a small channel in the nerve cell's membrane. That gate could be used to introduce the QX-314 and should potentially open new areas of research in anesthesia. Neurons that do not contain TRPV1 remain unaffected.

"The novelty of the idea here was that it might be possible that the QX-314 molecule might be small enough that you might be able to put it in through that small channel," said neurobiology professor Bruce Bean, from the Harvard Medical School.

Scientists now need to work on eliminating capsaicin’s other effects, like the burning sensation it produces. One way to achieve that is to change the injection order: first the QX-314 and quickly after that the capsaicin shot.