File:Synaptic potentiation cellular model hyperalgesia and allodynia.jpg

English: Synaptic potentiation as a cellular model for behavioural hyperalgesia and allodynia in chronic pain. (a) A model plot explains the hyperalgesia and allodynia in chronic pain conditions. Central plasticity causes the leftward shift of the input–pain response curve. The reduction of pain threshold into the non-noxious range possibly contributes at least partially to behavioural allodynia, whereas enhanced responses to the same noxious stimuli may contribute to hyperalgesia. (b) A model plot of synaptic responses versus stimulation intensity. Possibly, owing to changes in synaptic function (postsynaptic and presynaptic), the input–output curves shift leftward. These synaptic changes may contribute to behavioural hyperalgesia and allodynia at behavioural levels. Such changes may occur along sensory transmission pathways, from peripheral nociceptors, spinal dorsal horn synapses, thalamic neurons as well as cortical cells.