抄録
It is well known that patients with orofacial cancer suffer from cancer-induced pain. To understand mechanisms of pain by facial cancer, we have recently created a rat facial cancer model by inoculation with Walker carcinosarcoma 256 B-cells into the right vibrissal pad. The aim of the present study was to investigate changes of pain-related behavior and ingestive behavior in the model, along with c-Fos expression in the trigeminal subnuclei caudalis which is a center of facial pain sensation, by using both behavioral and immunohistochemical techniques. Mechanical allodynia and thermal hyperalgesia developed on the inoculated facial side on days 4 and 7 post-inoculation. After day 10, the sensitivities of the rats to mechanical and thermal stimuli were reduced, and there were physical difficulties in ingestion. Furthermore, the periods of facial grooming were prolonged post-inoculation, as compared with those in the sham group. In the trigeminal subnuclei caudalis, the level of c-Fos immunoreactivity of the ipsilateral side was increased significantly on days 4, 7 and 10 post-inoculation, as compared with those of the contralateral side and in the sham group. However, substance P and calcitonin gene-related peptide levels in the trigeminal subnuclei caudalis were not changed in the facial cancer model whereas they were increased in facial inflammation model of rat. These results suggest that neuropathic pains in the facial cancer model are probably caused by different pathway of inflamation-induced. [J Physiol Sci. 2008;58 Suppl:S164]
