[Pharmacological studies on degeneration and regeneration of peripheral nerves. (1) Effects of methylcobalamin and cobamide on EMG patterns and loss of muscle weight in rats with crushed sciatic nerve].

Experiments were performed to investigate the effects of Vitamin B12, i.e., methylcobalamin and cobamide, on the neural degeneration and regeneration. Male Wistar rats (140 to 150 g) under conditions of experimental unilateral sciatic nerve crushing were treated consecutively with methylcobalamin (50 and 500 mug/kg/day i.p.), cobamide (50 and 500 mug/kg/day i.p.) or saline. EMG recordings were periodically carried out and rats of each group were sacrificed to determine the weight-loss of denervated muscles 1, 2, 3 and 4 weeks after crush. Neither methylcobalamin nor cobamide exerted any significant effect on body-weight gain of the nerve-crushed rats with a daily injection of 50 and 500 mug/kg i.p.. The EMG pattern of the denervated biceps femoris muscle showed a total lack of fibrillation for 2 days after the nerve-crush. Thereafter, the fibrillation appeared and continued for 10 to 14 days until the nerve had regenerated, as evidenced by the appearance of a complex NMU voltage. The occurrence of fibrillation voltage was slightly delayed in methylcobalamin group (500 mug/kg/day) as compared with the saline control group. The re-appearance of normal NMU voltage was more rapid in the methylcobalamin 500 mug/kg group than in controls and other experimental groups. Neither methylcobalamin nor cobamide had any significant effect on the weight-loss of the gastrocnemius and tibialis anterior muscles following crush of the sciatic nerve. However, a daily injection of 500 mug/kg of methylcobalamin produced a significant increase in the weight of the soleus muscle which recovered to the extent of being the same weight of the contralateral 4 weeks after the nerve-crush. These results suggest that methylcobalamin may have an inhibitory effect on Wallerian degeneration and also a facilitatory effect on the neural regeneration of the crushed sciatic nerve of rats.