 Activation of the KOR is associated with spinal analgesia, miosis (pinpoint pupils), and psychotomimetic effects.The DOR is thought to play a role in analgesia.Although morphine does not bind to the σ receptor, it has been shown that σ receptor agonists, such as (+)-pentazocine, inhibit morphine analgesia, and σ receptor antagonists enhance morphine analgesia, suggesting downstream involvement of the σ receptor in the actions of morphine.