Historical perspective and modern views on pain physiology: from psychogenic pain to hyperalgesic priming

Abstract

The initial section summarizes the three conflicting concepts about pain already present at the end of the nineteenth centuries, i.e., the Specificity Theory, the Intensive-Summation Theory and the Pleasure Pain Theory and illustrates how, in the following decades, new experimental results partially support other innovative theories such as the Pattern Theory, the Central Summation Theory, the Fourth Theory of Pain and the Sensory Interaction Theory. The second half of the nineteenth century is characterized by the outburst of neurosciences that greatly affects the pain panorama: first of all the neurophysiological approach to nociception and the study of dorsal horn connectivity that leads to the formulation the Gate Control Theory, a genial intuition that is easily understood by clinicians and psychologists. At the same time the identification of nociceptors, the discovery of peripheral and central sensitization and the crucial role of inflammatory mediators such as prostaglandins and cytokines on nociceptive and neuropathic pain associated to the identification of endogenous opioids completely change the approach to pain management. More recently the pain research has been enriched by the advances in neuroimaging, neurobiology and genetics that allow new hypotheses about the mechanisms of development and maintenance of chronic pain.