Morphine at inflammatory experimental pain: A review

Pain is a complex entity that can be described in several dimensions, such as, acute pain and chronic pain, characterized by its duration. After the tissue injury, the activation of the sensory nervous tissue occurs from where the different pro-inflammatory mediators are released with the consequent nociceptive transmission that characterizes the genesis of inflammatory pain. The main objective of this study was to review the role of the opioid system, using morphine and MOR opioid receptors as paradigm, in the antinociceptive modulation of inflammatory pain, by means of the formalin test as a model. Various pieces of evidence are compiled that establish the fundamental role of morphine in the inflammatory pain. Morphine has noticeable antinociceptive efficacy in to decrease the inflammatory pain. This review demonstrates the fundamental role that morphine plays in inflammatory pain states and that it could serve as the basis for a new pharmacotherapy of inflammatory pain.