[Effects and mechanisms of osthole on sciatica induced by lumber disc herniation].

OBJECTIVE: To study the effects of osthole on sciatica induced by lumber disc herniation and its mechanisms.

METHODS: 54 male SD rats were randomly divided into 6 groups. Model (M) group (n = 12): Autologous nucleus pulposus was harvested from the tail and applied to the L5 dorsal root ganglion (DRG) and epidural space. Epidural catheterization was performed. Control(C) group (n = 12): On the basis of nucleus pulposus group, 50 microL tween-80 was administered epidurally on the day 6th after surgery. T2 (n = 6), T6 (n = 12), T13 (n = 6) and T20 (n = 6) group: 50 microL 2% osthole was administered epidurally on the 2th, 6th, 13th day and 20th after surgery respectively. General behaviors were observed and 50% paw withdrawal threshold (50% PWT) was measured 1 day before surgery, on the 1st, 3th, 7th,14th, 21th, 28th day after surgery, immediately before and 1 hour after osthole or tween-80 administration in each group. On the 7th day after surgery, the left L5 DRGs were obtained for detecting the expression of NOS and COX-2 in M, C and T6 group with 6 rats.

RESULTS: No lameness or autophagy was oberserved. 50% PWT decreased after surgery (P < 0.05). In T2 and T6 group, 50% PWT after osthole administration were significantly higher than those of M group and C group (P < 0.05), which recovered to the same level as 1 day before surgery (P > 0.05). In T13 and T20 group, 50% PWT 1 hour after osthole administration were significantly higher than those of M group and C group (P < 0.05), which recovered to the same level as 1 day before surgery (P > 0.05), but on days after 1 hour after administration, there was no significant difference when 50% PWT compared with M group or nucleus C group (P > 0.05). NOS positive cells and COX-2 positive cells were no significant difference when M group compared with C group (P > 0.05). But these positive cells in T6 group were significantly lower than those of M group and C group (P < 0.05).

CONCLUSION: 50 microL 2% osthole could completely inhibit the mechanical allodynia in the rat model of sciatica induced by lumbar disc herniation when it was administered epidurally on 2 or 6 day after surgery. But when administered on 13 or 20 day after surgery, its analgesic effect was transient. The effect of 50 microL 2% osthole epidural administration on day 6 after surgery on the rat model of sciatica induced by lumbar disc herniation may relate to inhibition of the expression of COX-2 and NOS in DRG.