Zeitschrift für Rheumatologie
-
The physiology of nociception involves a complex interaction of peripheral and central nervous system (CNS) structures, extending from the skin, the viscera and the musculoskeletal tissues to the cerebral cortex. The pathophysiology of chronic pain shows alterations of normal physiological pathways, giving rise to hyperalgesia or allodynia. After integration in the spinal cord, nociceptive information is transferred to thalamic structures before it reaches the somatosensory cortex. ⋯ Among the three subtypes of opioid receptors, mu- and delta-receptors either inhibit or potentiate NMDA receptor-mediated events, while kappa opioids antagonize NMDA receptor-mediated activity. Recently, CRH has been found to act at all levels of the neuraxis to produce analgesia. Modulation of nociception occurs at all levels of the neuraxis, thus, eliciting the multidimensional experience of pain involving sensory-discriminative, affective-motivational, cognitive and locomotor components.
-
Traditionally, opioids were considered the prototype of centrally acting analgesics. In the past decade a substantial literature has emerged demonstrating that opioids can produce potent and clinically measurable analgesia by activation of opioid receptors on peripheral terminals of primary sensory neurons. ⋯ Major recent findings in peripheral opioid analgesia include the relative lack of tolerance under inflammatory conditions, tetrapeptides as novel peripherally restricted compounds, the potent antiinflammatory activity of mu- and kappa-agonists and the identification of selectins as important molecules governing the homing of opioid cells to injured tissue. In addition to the extensively documented efficacy of locally applied morphine in post-surgical pain, clinical studies have now moved into the field of chronic arthritic pain.