Wide dynamic range neuron

The Wide Dynamic Range (WDR) Neuron was first discovered by Mendell in 1966. Early studies of this neuron established what is known as the Gate Control Theory. The basic concept is that non-painful stimuli block the pathways for painful stimuli, inhibiting possible painful responses. This theory was supported by the fact that WDR neurons are responsible for responses to both painful and non-painful stimuli, and the idea that these neurons couldn't produce more than one of these responses simultaneously. WDR neurons respond to all types of somatosensory stimuli, make up the majority of the neurons found in the dorsal horn of the spine, and have the ability to produce long range responses including those responsible for pain and itch.

WDR neurons are found in the posterior grey column of the spinal cord, with their cell bodies located in the posterior horn (dorsal horn). This area of the spinal cord houses two different types of neurons responsible for detection of pain: WDR neurons and Nociceptive Specific (NS) neurons. As the name implies, NS neurons give specific short range responses. WDR neurons are able to give long range responses for a large variety of stimuli giving them the ability to help identify the location and intensity of painful stimulation (sensory discrimination).

WDR neurons differ from most other neurons in that they experience what is called a ‘wind up’. This allows for the intensity of their response to increase with an increased frequency of stimulus. Most other neurons fire repeated action potentials of the same magnitude as a reaction to an increase in stimulus intensity. The intensity of the stimulus will only boost the frequency of action potentials, not their magnitude. However, WDR neurons exhibit increased action potential intensity with more presentations of a stimulus. This allows for plasticity of synapses and creates flexibility in the neuronal response. Though this may be of some benefit to the organism, this over excitation of the neurons can result in chronic pain.

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Wikipedia