[Effects of a nerve growth factor isolated and purified from the venom of Naja naja atra on injured sciatic nerve in the adult cat].

OBJECTIVE

To investigate the therapeutic effects of a nerve growth factor (NGF) isolated and purified from the venom of Naja naja atra on injured sciatic nerves in adult cat.

METHODS

Model of sciatic nerve crush lesion in 20 cats was made. After the operation, in the therapeutic group, NGF(2 micrograms/kg) was injected intramuscularly into the cat's leg once a day for 10 d (n = 5) and for 30 d (n = 5) respectively; in the control group, NGF was not injected and the cats were allowed to survive 10 d (n = 5) and 30 d (n = 5) respectively.

RESULTS

Ten days after the operation, the number of distal nerve fibers was significantly smaller in the control group than in the therapeutic group (P < 0.01); the reaction to planta stimulation appeared earlier and the leg action recovered faster in the therapeutic group. Thirty day after the operation, the number of distal nerve fibers in the therapeutic group was significantly greater than that of other groups (P < 0.01), but the histologic structure of the nerve fibers was in disorder and the axon and Ranvier node disappeared. About 16 days after injury and injection of NGF for consecutive days, the reaction to planta stimulation disappeared and leg paraplegia occurred in the operated side.

CONCLUSIONS

The results showed that NGF could obviously reduce the degeneration of nerve fibers and enhance the peripheral nerve regeneration and functional recovery from ingury early, but daily injection of NGF in the injured region for a long period could significantly result in over-regeneration of nerve fibers, and the conductive function of the injured peripheral nerves would be lost.