Objective:To explore the effect of spinal interleutkin-33 (IL-33) on radicular pain in rats modeling non-compressive lumbar disc herniation.Methods:A total of 80 male Sprague-Dawley rats were randomly divided into a sham operation group, a model group, a lentivirus negative control group, a low-dose IL-33 recombinant lentivirus group and a high-dose IL-33 group, each of 16. Non-compressive lumbar disc herniation was successfully induced in all except the rats in the sham operation group. Two days later, the model group was injected intrathecally with 10μl of enhanced infection solution. The lentivirus control group received 10μl of negative lentivirus, the low-dose IL-33 recombinant lentivirus group received 5μl of IL-33 recombinant lentivirus and the high-dose IL-33 recombinant lentivirus group received 10μl of IL-33 recombinant lentivirus. The 50% paw withdrawal threshold (50% PWT) was measured one day before the modeling and on the 1 st, 3 rd, 5 th, 7 th, 9 th, 11 th, 13 th, 15 th, 17 th, 19 th, and 21 st day afterward. On the 12 th day the expressions of IL-33 protein and mRNA were evaluated. Results:The average expression of IL-33 protein and mRNA in the model and the lentivirus negative control group increased significantly after the modelling compared with the sham group, while expression in the low- and high-dose IL-33 recombinant lentivirus groups was significantly lower than in the lentivirus negative control group. Compared with one day before the modelling, average 50% PWTs on the affected side decreased significantly in all of the modelling groups. From the 9 th to the 21 st day significantly increased 50% PWTs were observed on the affected side in the low-dose and high-dose IL-33 recombinant lentivirus groups compared with the other two modelling groups. Immunostaining showed significant increase in the expression of IL-33 in the dorsal horn of the spinal cord in the model group, compared with the sham operation group. Significant decrease in the average expression of IL-33 in the spinal dorsal horns was observed in the low-dose and high-dose IL-33 recombinant lentivirus groups. Conclusions:Intervertebral disk herniation may increase the expression of IL-33 in the spinal cord, and may cause radicular pain.