A team of international researchers have used a form of electro stimulation called transcranial direct current stimulation (tDCS) to release endrogenous opioids - the human body's most powerful painkillers that are similar in strength to morphine.  

This noninvasive procedure is especially significant and rather scary, as this is an immediate natural high, which can be accessed using damp sponges on your scalp, attached to a 9-volt battery.

tDCS is a frightening new frontier of neuroscience, which uses small electrical currents applied to the scalp (2 milliamps) to alter your brain's behaviour.  This procedure can improve your reaction times, make you learn things faster and now, it can release the human body's natural painkillers.  The diagram shows the difference of pain relief between one receiving no tDCS, and one who has.  Top = more pain; bottom = less pain.

The team of researchers, led by Alexandre DaSilva of the University of Michigan, applied the electrodes above the motor cortex, discovering that the tDCS treatment improved the patient's threshold for pain by 36%.  From the success shown, DaSilva is to commence with long term testing in the future, to see what different effects stimulating different regions of the brain has.  This, according to the paper, stops the requirement of pharmaceutical opiates; reducing the side effects and risk of addiction.  However, while the addiction maybe different in terms of being to a biological "reward" (like an orgasm) compared to the chemical "high" induced by pharmaceuticals, the immediacy and ease of access may make this extremely addictive.

Which makes things more troubling to say this technology is commercially available via a DIY tDCS kit.  We'd recommend you leave this to the professionals, and do not try this at home...seriously. Don't say we didn't warn you!

Source: Research paper: doi: 10.3389/fpsyt.2012.00093 – “Immediate effects of tDCS on the μ-opioid system of a chronic pain patient”

Jason England