At the push of a button: The brain mechanism that may eliminate pain
Researchers have identified a neural circuit in the brainstem capable of stopping neuropathic pain at its source. The goal: to develop targeted drugs that will prevent the danger of severe addiction to opioid painkillers.
"Off switch" in the brain: For millions of people around the world living with chronic neuropathic pain — intense pain resulting from damage to the nervous system — it is a daily reality filled with constant suffering. Now, researchers from the Washington University School of Medicine in St. Louis are presenting a discovery that may change the picture: they have identified a kind of "off switch" in the brain, capable of stopping and even reversing the sensation of pain.
The findings, published in the scientific journal Current Biology, open a new avenue for the development of targeted and effective pain treatments.
When the protective mechanism malfunctions
The study focuses on a tiny area in the brainstem called the locus coeruleus. In a normal state, this area is responsible for arousal, stress regulation, and the release of the neurotransmitter norepinephrine, and it helps in regulating and reducing pain signals arriving from the spinal cord. However, in a state of prolonged nerve damage, the system malfunctions: the locus coeruleus turns from a "pain reliever" into an engine that amplifies and accelerates chronic pain.
The treatments existing today — and primarily opioid drugs — do not provide an ideal solution.
"Traditional opioid drugs act on receptors throughout the body and brain, which leads to severe side effects, a decrease in the drug's effectiveness over time (tolerance), and a high risk of addiction," explains Jordan McCall, the senior author of the study.
The biological brake of pain
In a series of experiments on mouse models, the researchers discovered that specific receptors concentrated in the nerve cells of the locus coeruleus act as a biological brake. When these receptors are activated, the brain mechanism that amplifies pain signals turns off, and the pain decreases significantly.
To prove the mechanism, the researchers used genetic engineering. In the first stage, the researchers deleted the receptors solely from the nerve cells in the locus coeruleus. As expected, the sensitivity of the mice to heat and touch stimuli spiked radically. In the second stage, the researchers returned the receptors to those same nerve cells — and the hypersensitivity disappeared as if it had never been.
"We identified a neural circuit that acts as a brake and turns off continuous pain signals," noted McCall. "The fact that we succeeded in canceling the hypersensitivity indicates a direct path for turning off pain in the brainstem."
The main message of the study is the therapeutic potential: the development of drugs that will act in a targeted and precise manner only on the mu-opioid receptors in the locus coeruleus, instead of flooding the entire brain and body with addictive substances.
The research team is currently examining ways to selectively activate the neural "brake" they discovered. The goal is to create a new generation of drugs that will provide long-term relief to those suffering from chronic pain, and free them from dependence on dangerous painkillers.
