Effect of thiamine, dexamethasone and N-acetyl cysteine administration on axonal sprouting after sciatic nerve transection in rat

Regeneration of nerve fibers in transected nerve injuries requires formation of growth cone and axonal sprouting, proliferation of Schwan cells, myelin synthesis and etc. Pharmacological interventions are recommended to improve and promote these processes. In the present study the effects of thiamine, dexamethasone and N-acetyl cysteine administrations on axonal sprouting are examined.

After transection of right sciatic nerve of 24 male Wistar rats, the two ends of cut nerve were sutured into a piece of silicone tube. The rats were then divided into four groups (n = 6); receiving N-acetyl cysteine (150 mg/kg), dexamethasone (0.2 mg/kg), thiamine (50 mg/kg) and normal saline (control) once daily by intraperitoneal injection. At the end of treatment period (16 weeks) animals were sacrificed and the axonal sprouts removed and histologically examined.

There was no significant difference in the number of nerve fibers, axonal diameter and myelin sheath thickness among experimental groups. However, axonal diameter was almost increased in thiamine treated group (p=0.06). Moreover, a significant decrease (p < 0.05) in nerve cross sectional area was observed in dexamethasone group. The axonal diameter and myelin sheath thickness were also significantly decreased (p < 0.05) in dexamethasone group, compare to thiamine group.

Our data indicate that sciatic nerve regeneration in rats is inhibited by dexamethasone, might be ameliorated by thiamine, and is not changed by N-acetyl cysteine.