title: [Mechanism of spinal pain transmission and its regulation].
abstract: Morphine has been widely used for the treatment of acute, chronic, and cancer pain and is considered the strongest analgesic in clinical care. Conversely, morphine-induced analgesia may be accompanied by several side effects. Animal studies have demonstrated that low doses of morphine administered intrathecally can produce reliable analgesia for thermal, mechanical, and chemical nociceptive stimulation. On the other hand, high doses of morphine administered intrathecally may induce spontaneous nociceptive responses such as scratching, biting, and licking in mice as well as agitation and vocalization in rats. In addition, similar nociceptive responses including hyperalgesia, allodynia, and myoclonus have been observed in humans following intrathecal or systemic administration of high-dose morphine. It has been suggested that the spontaneous nociceptive behaviors evoked by high-dose morphine may be mediated by a non-opioid mechanism that is not yet fully understood. This review describes the mechanisms of spontaneous nociceptive behaviors evoked by high-dose morphine focusing on the neurotransmitters/neuromodulators released from primary afferent fibers.
authors.affiliation: Department of Physiology and Anatomy, Tohoku Pharmaceutical University.
authors.forename: Chizuko
authors.initials: C
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D006801:Humans; D009020:Morphine / Q000627:therapeutic use; D010146:Pain / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology*; D010166:Palliative Care; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D009020:Morphine