To investigate the effect of local nerve block with ropivacaine on nerve regeneration after sciatic nerve injury repair in rats and explore its possible mechanism.

Sixty male SD rats were randomly divided into control group and ropivacaine group. The repair model of peripheral nerve injury was made in all rats by using an end-to-end suture of epineurium after the right sciatic nerve was severed. The ropivacaine group was infused with 0.2% ropivacaine at a rate of 0.1 ml/h for 3 days at the injured site, while the control group was infused with the same volume of normal saline. Then the nerve block effect of ropivacaine was observed, and the changes in behavior, electrophysiology, regeneration nerve fiber morphology, myelin basic protein expression of distal sciatic nerve and macrophage infiltration were detected at each corresponding time point.

At 8 weeks after operation, compared with the control group, the behavioral results showed that the thermal latency and footprint length of ropivacaine group were significantly decreased (P<0.05); the electrophysiological results showed that the amplitude recovery index of compound muscle action potential in ropivacaine group was significantly increased (P<0.05), but there was no significant difference in latency and conduction speed recovery index between the two groups (P>0.05); the immunofluorescence results showed that the area of regenerated axons in ropivacaine group was significantly increased (P<0.05), but there was no significant difference in the area of regenerated myelin sheath between the two groups (P>0.05); transmission electron microscopy results showed that the diameter of regenerated axons, the thickness of myelin sheath and the number of unmyelinated axons in ropivacaine group were significantly increased (P<0.05), but there was no significant difference in the number of myelinated axons between the two groups (P>0.05). In the early postoperative period, western blotting results showed that the clearance rate of myelin basic protein was significantly increased in ropivacaine group (P<0.05); immunofluorescence results showed that the number of macrophages in ropivacaine group was significantly increased (P<0.05).

The local nerve block with ropivacaine promotes axonal regeneration of injured sciatic nerve in rats through recruitment of macrophages to accelerate clearance of myelin fragments.

Peripheral nerve; Regeneration; Ropivacaine; Macrophage infiltration