Bruce Pomeranz (the neuroscientist who showed that electric acupuncture analgesia is mediated through the stimulation of the release of neurotransmitter, in particular, endorphins) has come up with a second "scientific" explanation of mechanisms through which acupuncture works.

The skin of vertebrates acts like a battery: there is a voltage across the skin.

"An outstanding study was published by Jaffe et al showing that the human skin has a resting potential across its epidermal layer of from 20 to 90 mV (outside negative, inside positive). ..." (Pomeranz):

Electricity, in the body, acts as a signal to turn on healing. DC fields influence the migration of cells (for instance, in wound healing), the growth of nerves...

Because there is a voltage across the skin, when we cut ourselves a current flows, the "current of injury" and this current is a signal that turns on various of the healing responses.

Acupuncture causes a current of injury and through this turns on healing responses.

"Preliminary studies on normal human volunteers in our laboratory indicate that needling the skin produces decrease of local skin resistance which lasts 1-2 days.* A simple calculation using Ohm's law suggests to us that a small hole created by an acupuncture needle can create sufficient current of injury (10muA) to be of possible benefit to tissue growth and regeneration. It should be noted that these tiny currents would not be sufficient to initiate nerve impulses." (Pomeranz):

"[The articles] from our lab also show enhanced nerve growth towards the negative pole of the applied DC field. Holes made by needles would also cause a negativity at the site of injury, due to the current of injury." (Pomeranz):

I once asked Bruce how far he thought that these mechanisms could explain the clinical effects of acupuncture. He hazarded that the endorphin mechanism might account for 10 to 15% of acupuncture, and guessed that the current of injury might account for another 5%. As for the rest, look to future science, and TCM.

* Excuse me. I have to boast. This is work I was involved in.