Below is an instruction from Human. Write a response.
    ### Instruction:
    what research (or clinical trials) is being done for Chronic Pain ?
    ### Response:
    Clinical investigators have tested chronic pain patients and found that they often have lower-than-normal levels of endorphins in their spinal fluid. Investigations of acupuncture include wiring the needles to stimulate nerve endings electrically (electroacupuncture), which some researchers believe activates endorphin systems.
    