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Leu-enkephalinEndorphins are powerful and safe opioids that the body produces. Endorphins bind to opioid receptors in the brain. The same receptors are also used by opioid medications.

Recent studies using the brain-imaging technology showed that taking placebos leads to neurobiological patterns in the brain that can also be observed when powerful pain relievers are given. Petrovic et al (2002)demonstrated that the same regions of the brain are activated when patients receive an opioid pain reliever (remifentanil) or when patients take a placebo. Similar brain imaging studies by Zubieta et al (2005) and Eippert et al (2009) also showed that placebos trigger brain responses that ameliorate pain.

For those who are interested in learning more about fascinating field of brain imaging in Neuroscience, the studies described here used two techniques to generate high definition, three dimensional images of brain function:

Positron Emission Tomography (PET)

PET measures metabolism and the flow of blood to different parts of the brain. PET is a non-invasive method that also allows for some movement during the scan, but it does expose patients to radiation from a biologically active tracer molecule.

Functional Magnetic Resonance Imaging (FMRI)

Similar to PET scans, FMRI measures blood-flow in the brain. FMRI has the advantage that a radioactive tracer molecule it not needed. The image resolution of FMRI is also better than PET. However, since patients need to remain still during FMRI scans, this imaging method cannot be used for experiments where, e.g., patients need to read out words during a scan. Redesigned equipment and advancements in computing power are likely to overcome this barrier in the future.

image: Leu-enkephalin