fMRI and PET Opioid Imaging Investigation of the Expectancy Component of Acupuncture Analgesia in Health and Disease

We propose to use quantitative brain imaging methods (fMRI and PET [11C]diprenorphine opioid receptor binding) to investigate the neurobiological mechanism of acupuncture analgesia, placebo analgesia and their interrelationship.

The initial approach is to study healthy subjects using a well tested method to manipulate their expectation of pain relief from treatment. We combine this manipulation with acupuncture analgesia and sham acupuncture analgesia to create a 2 X 2 neuroimaging comparison of verum (real) acupuncture and sham acupuncture each paired with positive and negative expectancies. We measure fMRI signal changes caused by application of calibrated painful stimuli and subsequent evaluation of pain intensity after the different treatments. The patterns of fMRI signal changes will identify critical brain networks involved in acupuncture and placebo analgesia.

We hypothesize that expectancy (placebo) analgesia, will produce analgesia by activating descending endogenous opioid systems as well as by activating what we have called the selective pain intensity evaluation distortion process. The first mechanism may also be shared with acupuncture analgesia;however, the second mechanism should be unique for placebo analgesia.

We are developing methods to extend this experimental paradigm to a cohort of chronic low back pain patients with specific controls for psychiatric co-morbidity. We are also using PET [11C] diprenorphine opioid receptor binding changes to investigate the role of endogenous opioid neurotransmission in mediating acupuncture analgesia.

This project completes the requirements to allow our research group to study the mechanisms of acupuncture in animal models, healthy and chronic pain subjects. This forms a beneficial cycle and
provides a powerful model for acupuncture research.