Windup in the spinal cord

Abstract

One of the most fundamental features of nociception is the sensitization of neuronal responsiveness that manifests as an increase in action potential activity to repeated nociceptive input. This sensitization can occur at all levels of the neuraxis including the primary afferent nociceptor, neurons within the dorsal and ventral horn of the spinal cord as well as supraspinal neurons. Because of its overall importance as a model for synaptic plasticity, sensitization of response of post-synaptic neurons has been widely studied. In the context of nociception, sensitization of the response of post-synaptic neurons in the mammalian spinal cord has received intensive attention. Sensitization of neuronal responsiveness takes many forms, one of the simplest that can be observed in both dorsal horn interneurons and ventral horn motoneurons is known as 'windup' (WU). Windup refers to the incrementing discharge of action potentials that may be recorded from post-synaptic dorsal or ventral horn neurons in response to the application of repetitive, low frequency, short duration (electrical) stimuli applied to an afferent input. In this chapter, I will describe the windup phenomenon and define its relationship with central sensitization.