Articles: chronic-pain.
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Opioid receptor antagonists increase hyperalgesia in humans and animals, which indicates that endogenous activation of opioid receptors provides relief from acute pain; however, the mechanisms of long-term opioid inhibition of pathological pain have remained elusive. We found that tissue injury produced μ-opioid receptor (MOR) constitutive activity (MOR(CA)) that repressed spinal nociceptive signaling for months. ⋯ Thus, MOR(CA) initiates both analgesic signaling and a compensatory opponent process that generates endogenous opioid dependence. Tonic MOR(CA) suppression of withdrawal hyperalgesia may prevent the transition from acute to chronic pain.
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Chronic pain and major depression commonly occur together. Major depression in patients with chronic pain is associated with decreased function, poorer treatment response and increased health care costs. ⋯ The diagnosis of major depression in patients with chronic pain requires differentiation between the symptoms of pain and symptoms of physical illness. Antidepressants and psychological therapies can be effective and should be delivered as part of a coordinated, cohesive, multidisciplinary pain management plan.