RT Journal Article SR Electronic T1 Placebo Effects Mediated by Endogenous Opioid Activity on μ-Opioid Receptors JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 7754 OP 7762 DO 10.1523/JNEUROSCI.0439-05.2005 VO 25 IS 34 A1 Jon-Kar Zubieta A1 Joshua A. Bueller A1 Lisa R. Jackson A1 David J. Scott A1 Yanjun Xu A1 Robert A. Koeppe A1 Thomas E. Nichols A1 Christian S. Stohler YR 2005 UL http://www.jneurosci.org/content/25/34/7754.abstract AB Reductions in pain ratings when administered a placebo with expected analgesic properties have been described and hypothesized to be mediated by the pain-suppressive endogenous opioid system. Using molecular imaging techniques, we directly examined the activity of the endogenous opioid system on μ-opioid receptors in humans in sustained pain with and without the administration of a placebo. Significant placebo-induced activation of μ-opioid receptor-mediated neurotransmission was observed in both higher-order and sub-cortical brain regions, which included the pregenual and subgenual rostral anterior cingulate, the dorsolateral prefrontal cortex, the insular cortex, and the nucleus accumbens. Regional activations were paralleled by lower ratings of pain intensity, reductions in its sensory and affective qualities, and in the negative emotional state of the volunteers. These data demonstrate that cognitive factors (e.g., expectation of pain relief) are capable of modulating physical and emotional states through the site-specific activation of μ-opioid receptor signaling in the human brain.