抄録
In order to clarify the involvement of the primary afferent neurons for an induction of the neuropathic pain in the trigeminal region, we developed the neuropathic pain model in the SD rats with chronic constriction nerve injury (CCI) of the inferior orbital nerve (ION). Two ligatures were applied to the ION of the rats through the oral cavity. Mechanical allodynia was observed at 3 days after ION-CCI and lasting more than 14 days. We could not observe thermal allodynia in the rats with ION-CCI. At 3, 5, 7 and 14 days after application of two ligatures around the ION, single unit activities were recorded from ION under general anesthesia with 1-2% halothane. C, Aδ and Aβunits were defined on the basis of the conduction velocity calculated from the distance between recording and stimulation sites and antidromic latency from the brain stem. These three types of units were recorded at the early stage of the ION-CCI. The longer time was passed after the ION-CCI, the more frequently Aδ units were recorded. The highest spontaneous activity was recorded at 3 days after CCI during observation period. This high frequency firing was progressively decreased after that, but that was still higher than naïve at 14 days after the CCI. The mechanical and cold responses of the Aδ units were also highest at 3 days after the ION-CCI and progressively decreased after that. These suggest that the abnormal primary afferent firing observed in the rats with ION-CCI would be involved in neuropathic pain in the trigeminal region. [Jpn J Physiol 54 Suppl:S173 (2004)]
