The biological basis of pain

Journal/Book: Int Rev Psychiatr. 2000; 12: Rankine Rd, Basingstoke Rg24 8Pr, Hants, England. Carfax Publishing. 128-147.

Abstract: Pain is characterized not only by location and quality, but also in emotional terms (terrifying, unbearable agonising). Pain has an essential duality It is both sensation and emotion. Psychiatrists are increasingly involved with diagnostic assessment of pain patients. Many treatments involve medications and techniques familiar to psychiatrists. Skill in these tasks requires familarity with pain physiology. The concept of chronic pain as an extension of acute nocicepnive gain is not valid, particularly in neuropathic pain. Chronic pain is often an evolving process in which injury may produce one pathogenic mechanism, which in turn produces others, so that the cause of pain changes over time. Ectopic primary afferent discharge may injure spinal inhibitory neurons, leading to hyperexcitability owing to disinhibition. Animal and human data indicate that dorsal root damage evokes a slowly evolving abnormality in spinal cord neurons, which generate abnormal responsiveness of thalamic neurons, which generates cortical dysfunction. Over time, these higher-level abnormalities may become independent of the abnormalities that generated them. Clearly, pain perception is less a moment-to-moment analysis of afferent input than a dynamic process influenced by the effects of past experiences. Sensory stimuli act on neural systems, which have been,modified by past inputs, and the behavioral output is significantly influenced by the 'memory' of these prior events.

Note: Review Covington EC, Cleveland Clin Fdn, Dept Psychiat & Psychol, Chron Pain Rehabil Program, 9500 Euclid Ave, Cleveland,OH 44195 USA

Keyword(s): SPINOTHALAMIC TRACT NEURONS; PROTEIN-KINASE-C; PERIPHERAL-NERVE INJURY; DORSAL-ROOT GANGLION; EXCITATORY AMINO-ACIDS; SYMPATHETICALLY MAINTAINED PAIN; CHRONIC CONSTRICTION INJURY; PRIMARY AFFERENT NEURONS; PRIMARY SENSORY NEURONS; SPINAL-CORD NEURONS

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