Enhanced responses of rat dorsal horn neurons after UV irradiation of the hindpaw; roles of the NMDA receptor.

Recordings were made from nociceptive dorsal horn neurones in the anaesthetized rat 3 and 5 days after ultraviolet (UV) irradiation of the hindpaw. The electrically evoked A beta-fibre-evoked responses from the paw were enhanced and their thresholds were lowered. Spontaneous neuronal activity was increased but the C-fibre-evoked responses were unaltered. These enhanced responses, suggestive of allodynia, were reduced by N-methyl-D-aspartate receptor (NMDA) antagonism.