Brain scientists are searching for ways to develop highly effective pain medicines without the potential side effects of opioids, which include nausea, breathing suppression, and addiction. Opioid analgesics produce their useful and harmful effects by attaching to different types of proteins (opioid receptors) that then control cell signaling. New opioid drugs that bind to a specific type of opioid receptor (kappa receptor) can produce pain suppression without addiction. However, their use has been limited by dysphoria (negative emotions). Recently, scientists have identified some kappa opioids without that negative effect.
In this NIDA-funded research, scientists used a novel approach to compare the cell signaling initiated by kappa opioids that produce dysphoria from those that do not. Using this development, they discovered a new cellular pathway that mediates the dysphoria of kappa opioids. This finding will facilitate the design of new pain medicines that lack these adverse effects.