It has been known for decades that the brain has its own pain-relieving chemicals. They are called endogenous “opioids,” because of their similarity to opium-derived drugs like morphine. These opioids are released in the brain in response to a painful event, bind to receptors on selected nerve cells, and activate nerve pathways to the area where you hurt to inhibit your pain. Unfortunately they don’t work very well in cases of chronic pain.
New studies conducted by investigators at the Molecular and Behavioral Institute at the University of Michigan, led by Alexandre F.M. DaSilva and TMD researcher Jon-Kar Zubieta, suggest that you can stimulate the brain to ramp up its output of these pain-relieving chemicals to treat chronic pain. They report a case study of a woman with severe pain following an attack of shingles (post-herpetic neuralgia) that affected an area around her left eye and the middle of her face on the left side. In an initial brain imaging scan using positron emission tomography (PET), the investigators used radioactive tracers to identify areas in the brain rich in cells whose outer membranes contained binding sites for “mu-opioid” molecules. These sites bind some of the brain’s most potent endogenous opioids. In a second PET scan they applied very weak electrical stimulation directly to the scalp above the motor cortex of the brain, the area controlling voluntary movement. Following this “transcranial Direct Current Stimulation” or tDCS, the team noted a reduction in the availability of mu-opioid binding sites, meaning that the sites were now filled with endogenous opioids able to activate pain-inhibiting nerve pathways. The initial electrical stimulation to the brain was not sufficient to relieve the patient’s facial pain, but sensory testing showed that her tolerance to severe cold had increased markedly.
The researchers believe that repeated sessions of brain stimulation will be necessary to relieve chronic pain, and certainly more chronic pain patients need to be studied. But the approach has an exciting appeal: you would be recruiting the brain’s own means of relieving pain and not subjecting the patient to invasive surgery or to the use of morphine or similar pain drugs, which affect other systems in the brain besides pain and have unwanted side effects.