The Ying and Yang of Pain: Protective Versus Damaging

Abstract

Clinical pain is a serious public health problem. Effective treatment of suffering associated with pain depends on specific knowledge of how pain signals are initiated, processed, interpreted and then transmitted. In the case of chronic pain, these pain signals are also perpetuated. Nociceptors are primary sensory neurons that specialize in detecting both intense and noxious stimuli and for this reason, they represent a warning system, the first line of defence against potentially harmful, threatening or damaging environmental inputs. In other words, nociceptors are crucial to deal effectively with danger because they sense it and let us know about it. In addition to sensing noxious stimuli, nociceptors contribute to the reactions needed to avoid them. This results in rapid withdrawal and in experiencing an intensely unpleasant or painful sensation. These reactions are essential to maintaining the body’s integrity. Thus, nociceptive (mostly acute) pain is an adaptive alarm system key to survival. However, persistent (chronic) pain is maladaptive, that is, an ongoing false alarm. In this chapter we will summarize our current understanding of the pain process, focusing on the central aspects of acute and chronic pain. We highlight how nociceptors originate during development and their intrinsic properties that enable them to transduce, conduct, and transmit nociceptive information. We also explore possible solutions to the problem and offer new perspectives on the treatment of pain from both cellular- and systemic viewpoints.