The current findings help explain what happens in the brain that decreases pain during the brief sessions of electricity, says Dr. Alexandre DaSilva, an assistant professor of biologic and materials sciences at the University of Michigan School of Dentistry and director of School’s the Headache and Orofacial Pain Effort Lab.
In their recent study, Dr. DaSilva and colleagues intravenously administered a radiotracer that reached important brain areas in a patient with trigeminal neuropathic pain (TNP)—a type of chronic, severe facial pain. They applied the electrodes and electrically stimulated the skull right above the motor cortex of the patient for 20 minutes during a positron emission tomography scan. The stimulation is called transcranial direct current stimulation. The radiotracer was specifically designed to measure, indirectly, the local brain release of mu-opioid, a natural substance that alters pain perception. In order for the opiate to function, it needs to bind to the mu-opioid receptor (the study assessed levels of this receptor).
“This is arguably the main resource in the brain to reduce pain,” Dr. DaSilva says. “We’re stimulating the release of our [body’s] own resources to provide analgesia. Instead of giving more pharmaceutical opiates, we are directly targeting and activating the same areas in the brain on which they work. [Therefore] we can increase the power of this painkilling effect and even decrease the use of opiates in general, and consequently avoid their side effects, including addiction.”
The dose of electricity is very small, and just one session immediately improved the patient’s threshold for cold pain by 36%, but not the patient’s clinical, TNP/facial pain. These results suggest that repetitive electrical stimulation during several sessions is required to have a lasting effect on clinical pain as shown in their previous migraine study, comments Dr. DaSilva.
The manuscript appears in the November 2012 issue of the journal Frontiers in Psychiatry. The authors just completed another study with more subjects, and the initial results seem to confirm the findings above, but further analysis is necessary.
(Source: University of Michigan News Service, January 2, 2013, ns.umich.edu/new/)