Pain wind-up

Pain wind-up is the increase in pain intensity over time when a given stimulus is delivered repeatedly above a critical rate. It is caused by repeated stimulation of group C peripheral nerve fibers, leading to progressively increasing electrical response in the corresponding spinal cord (posterior horn) neurons due to priming of the NMDA receptor based response.^[1][2] It describes an exponentially progressive increase in firing of WDR neurons with repeated stimulation.