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Electrical Brain Stimulation Releases Opiate-Like Painkiller

Researchers use new approach to treat severe facial pain (Jan. 2)

Researchers at the University of Michigan have used electricity on certain regions in the brain of a patient with chronic, severe facial pain to release an opiate-like substance that’s considered one of the body’s most powerful painkillers.

The findings expand on previous work in which the investigators delivered electricity through sensors on the skulls of patients with chronic migraine, and found a decrease in the intensity and pain of their headache attacks. However, the researchers couldn’t completely explain how that was accomplished.

The new findings — published in Frontiers in Psychiatry — help explain what happens in the brain that decreases pain during the brief sessions of electricity.

The researchers administered an intravenous 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 directly above the motor cortex of the patient for 20 minutes during a positron emission tomography (PET) scan. This technique is known as transcranial direct current stimulation (tDCS).

The radiotracer was designed to measure indirectly the local brain release of mu-opioid — a natural substance that alters pain perception. For an opiate drug to function, it must bind to this receptor.

“This is arguably the main resource in the brain to reduce pain,” said Dr. Alexandre DaSilva. “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 mu-opioid receptors in the brain, DaSilva said.

Electroconvulsive therapy (ECT), which is used to treat depression and other psychiatric disorders, uses amperage in the brain ranging from 200 to 1,600 milliamperes (mA). The tDCS protocol used in the new study delivered 2 mA — considerably lower than ECT.

One session of treatment immediately improved the patient’s threshold for cold pain by 36%, but not the patient’s clinical TNP pain. This suggests that repetitive electrical stimulation over several sessions is required to have a lasting effect on clinical pain, as shown in the previous migraine study, DaSilva said.

Source: University of Michigan; January 2, 2013.

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