Thank God for the mu opioid receptor! This receptor mediates the most profoundly merciful balm to the most afflicted among us. No pain is refractory to the mu opioid receptor’s ability to dull its sharp edges and ease the suffering soul. If only the actions of the mu opioid receptor stopped there. Unfortunately, the mu opioid receptor is associated with side effects ranging from mild (ileus, urinary retention, itching, hyperalgesia) to respiratory depression, apnea, coma and death. Even worse, the pharmaceutical ligands for the mu opioid receptor are among the most addictive substances on earth.
Why does this receptor even exist? What survival advantage is conferred by a receptor that mediates profound analgesia accompanied by life-threatening apnea? Is there any setting where profound analgesia and apnea might be desirable?
The answer might be found in our first minutes of life. Among life’s many miracles, perhaps none are as amazing as...
