Chronic Opioid Therapy and Opioid Tolerance: A New Hypothesis

Figure 5

Opioid receptors in thalamus (red) and secondary somatosensory cortex, S2 (arrow). Photo Researchers Picture Number: SF2687. Credit: Philippe Psaila/Photo Researchers, Inc. License: Rights Managed. Description: Opioid receptors. Colored frontal Positron Emission Tomography. (PET) scan showing the normal distribution of opioid receptors in the human brain. By injecting a patient with an opioid tagged with carbon-11 (radioactive tracer), a color-coded scan is produced, showing the concentration of opioid receptors from red (highest) through yellow and green to blue (lowest).