Electric stimulation on the brain of a patient with chronic, severe facial pain released an opiate-like substance that’s considered one of the body’s most powerful painkillers, according to new research.
Alexandre DaSilva, assistant professor of biologic and materials sciences at the U-M School of Dentistry and director of the school’s Headache & Orofacial Pain Effort Lab and colleagues intravenously administered a radiotracer that reached important brain areas in a patient with trigeminal neuropathic pain (TNP). They applied the electrodes and electrically stimulated the skull right above the motor cortex of the patient for 20 minutes during a PET scan (positron emission tomography). The stimulation is called transcranial direct current stimulation (tDCS).
The radiotracer was specifically designed to measure, indirectly, the local brain release of m-opioid, a natural substance that alters pain perception. In order for opiate to function, it needs to bind to the m-opioid receptor (the study assessed levels of this receptor).
“This is arguably the main resource in the brain to reduce pain,” DaSilva said. “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 pain-killing effect and even decrease the use of opiates in general, and consequently avoid their side effects, including addiction.”
Most pharmaceutical opiates, especially morphine, target the m opioid receptors in the brain, DaSilva said.
Just one session immediately improved the patient’s threshold for cold pain by 36 percent, but not the patient’s clinical, TNP/facial pain. This suggests that repetitive electrical stimulation over several sessions are required to have a lasting effect on clinical pain as shown in their previous migraine study, DaSilva says.
Next, researchers will investigate long-term effects of electric stimulation on the brain, even though the dose of electricity used is very small, and find specific targets in the brain that may be more effective depending on the pain condition and patients’ status. For example, the frontal areas may be more helpful for chronic pain patients with depression symptoms.
