Hot pepper mixture for pain relief

An Israeli researcher at Harvard has developed a method to eliminate pain sensations without paralyzing the anesthetized area

Imagine an epidural injection or a local anesthetic injection that will not paralyze your legs and your ability to move, yet completely block the pain. This treatment is already within our reach. And the result - childbirth, back surgery and dental treatment can be much less traumatic. This is thanks to the research work of Dr. Alexander Binstock, an Israeli researcher who is in post-doctoral training at Harvard, and his colleagues from Harvard Medical School and Massachusetts General Hospital, who were able to show in rats that it is possible to block nerve cells that mediate the sensation of pain in a unique way without harming other sensations. or in the ability to move.
The rats received a local injection into the area of ​​the nerve that innervates their hind limbs and subsequently lost the ability to feel pain but moved normally and responded to other sensory stimuli. The injection included the substance QX-314, an inactive derivative of the local anesthetic lidocaine, as well as capsaicin, which is the "hot" substance in red pepper. The combination of these substances uniquely paralyzed pain fibers and prevented them from transmitting painful signals to the brain.
"We were able to target a local anesthetic to a specific population of nerve fibers," explained Dr. Alexander Binstock, author of the article that appeared in the latest edition of the prestigious scientific journal Nature. "Now we can block the activity of the pain fibers without interfering with the nerve fibers that control movement or perceive various non-painful sensations such as heat, cold and touch. We are optimistic and hope that when the method is applied to humans, it will change the experience of various medical procedures from childbirth to dental treatments," adds Dr. Binstock.
Despite a continuous effort by the pharmaceutical industry, the treatment of pain has hardly changed since 1846. That year, in the same hospital where the authors of the article work, surgery was performed under general anesthesia for the first time. The substances they used then and still use today, work by blocking all nerve cells and not just nerve cells that transmit pain. Therefore, these drugs cause a variety of side effects, such as: loss of consciousness in general anesthesia and paralysis in local anesthesia.
The new method uses a protein called TRPV1 which is unique to nerve cells that transmit pain sensations. TRPV1 creates a wide channel where molecules can enter and exit the cell. Under normal conditions, passage through the canal is blocked by a gate-like structure. The aforementioned gate opens only when the cells are exposed to high heat or to a component of hot pepper called capsaicin. Other neurons do not express TRPV1 and are therefore unaffected by capsaicin.
Since the anesthetics in clinical use today penetrate every nerve cell, and therefore block the activity of all types of nerve, the researchers needed a different anesthetic that does not penetrate every cell. The new method uses QX-314, a derivative of the anesthetic lidocaine that Anna is able to pass through the cell membrane. Because of this, when QX-314 is injected alone into the tissue it is not able to penetrate nerve cells and block their action and is therefore not in clinical use.
However, when pain-transmitting neurons are exposed to capsaicin, the gates of TRPV1 channels open, allowing QX-314 to enter the neurons and block their activity. Since the substance cannot enter cells that do not have TRPV1, such as nerve cells that control movement and transmit touch sensations, it does not harm their operation.
To test the method, Binstock injected the materials into the paws of rats and tested their ability to tolerate painful stimuli. The animals did not respond at all to their painful stimuli or only responded to stimuli with a much higher intensity than usual. The animals developed immunity to pain but continued to move normally and responded normally to non-painful stimuli.
The team still has to overcome several hurdles before the method can be applied to humans. Since capsaicin itself causes sensations of irritation and pain, first and foremost they must find a substance that will open TRPV1 channels and not cause pain until QX314 takes effect. The researchers are sure they will succeed.
"Ultimately, this method may completely change the method of anesthesia in surgery as well as the treatment of postoperative pain by allowing the patient to remain alert without feelings of pain or paralysis," said Dr. Binstock. "Normal sensation and the ability to move without pain will speed up the recovery and rehabilitation after surgeries and injuries and will consequently improve the success rates of the surgeries. In addition, the method can be effective in treating inflammatory and chronic pain."
Dr. Alexander Binstock, 35 years old, born in the former Soviet Union, immigrated to Israel at the age of 18. He holds a bachelor's degree from Ben Gurion University. After his military service, he completed doctoral studies in neuroscience at the Hebrew University, in the laboratory of Prof. Mike Gutnick, where he studied properties of nerve cells in the sensory cortex. These days he is a researcher in the pain research laboratory at Harvard University, where he tests various mechanisms of inflammatory and chronic pain and develops innovative methods for pain treatment.