Principles & Practice of Pain Medicine > Part I. Pain: Biology, Anatomy, and Physiology > Chapter 3. Pathophysiology of Pain Stephen A. Cohen

Peripheral Sensitization

"Unmyelinated C or thinly myelinated A afferent fibers convey pain sensation. Minor irritation of tissue in a neuron's receptive field results in the release of inflammatory mediators, which is often accompanied by a reduction in the nociceptor threshold. Such a change, called peripheral sensitization, renders the nerve ending responsive to weak, normally nonpainful stimuli (allodynia). Stronger stimuli typically provoke exaggerated pain (hyperalgesia). Sensitization involves not only normal nociceptive fibers but also the recruitment of so-called silent nociceptors, which are not usually sensitive to painful stimuli or inflammatory substrates such as prostaglandins or bradykinin...."