中文摘要：

目的：观察腹外侧眶皮层（ventrolateral orbital cortex,VLO）内微量注射谷氨酸对大鼠后爪注射福尔马林诱发的腰段脊髓背角Fos表达的抑制效应以及该效应是否通过中脑导水管周围灰质（PAG）下行抑制系统介导。方法：免疫组织化学染色技术。结果：（1）VLO内微量注射谷氨酸（100nmol/0.5μl）明显抑制大鼠后爪注射福尔马林诱发的脊髓背角Fos表达,与注射生理盐水相比,差异显著（P〈0.001）,并且这种抑制效应可被VLO内预先注射非选择性谷氨酸受体拮抗剂kynurenic acid（2nmol/0.5μl）所翻转,与单独注射谷氨酸相比差异显著（P〈0.001）,但与注射生理盐水相比无显著差异（P〉0.05）;（2）双侧腹外侧PAG内微量注射局麻剂利多卡因（0.2nmol/0.5μl）可以明显阻断VLO内微量注射谷氨酸（100nmol/0.5μl）对大鼠脊髓背角Fos表达的抑制效应,与单独注射谷氨酸相比差异显著（P〈0.001）,而双侧腹外侧PAG内微量注射生理盐水不影响VLO内微量注射谷氨酸对大鼠脊髓背角Fos表达的抑制效应（P〉0.05）。结论：VLO内谷氨酸可能通过其受体激活PAG脑干下行抑制系统在脊髓水平抗炎性持续性伤害感受效应。

英文摘要：

Objective：To investigate the possible inhibitory effect of microinjection of glutamate into the ventrolateral orbital cortex（VLO）on the Fos expression in the lumbar dorsal horn neurons induced by formalin injection into the rat hindpaw.The modulatory effects of the descending inhibitory system origining from the periaqueductal gray（PAG）were also examined.Methods：Immunohistochemical staining technique was used.Results：（1）Microinjection of glutamate（100 nmol/0.5 μl）into the VLO depressed the Fos expression in the lumbar dorsal horn neurons induced by formalin injection with a statistically significant difference（P〈0.001）as compared with that obtained from saline injection into the VLO,and this effect could be antagonized by application of the non-selective glutamate receptor antagonist kynurenic acid（2 nmol/0.5 μl）into the same VLO site.The statistical difference was significant as compared with that of injection of glutamate alone（P〈0.001）,but no statistical difference as compared with that injected with saline（P〉0.05）.（2）Microinjection of lidocaine hydrochloride,a local anesthetic（0.2 nmol/0.5 μl,each side）bilaterally into the ventrolateral parts of the PAG（vlPAG）completely eliminated the VLO glutamate-induced inhibition on the Fos expression in the lumbar dorsal horn neurons induced by formalin with a statistically significant difference（P〈0.001）as compared with that obtained from glutamate injection alone into the VLO,while bilaterally microinjection of saline into the vlPAG has no influence on the VLO glutamate-induced inhibition of the Fos expression in the lumbar dorsal horn neurons（P〉0.05）.Conclusion：Glutamate and its receptors in the VLO are involved in mediating the descending antinociceptive effect on persistent inflammatory nociception via activation of the PAG brainstem descending inhibitory system and depressing the nociceptive transmission at the spinal cord level.