Comparison of anti-inflammatory effects of dexamethasone and thiamine on Wallerian degeneration after sciatic nerve transection in rat

Wallerian degeneration is aninnate immune response which occurs after nerve injury. In this study, the effects of dexamethasone (Dex) and thiamine (Thi), as anti-inflammatory drugs, were compared on the Wallerian degeneration.

The right sciatic nerve of 45 male rats was transected and the rats were divided into five groups (n=9). Animals in groups 2 to 5 daily received (i.p) low and high doses of Dex and Thiup until sampling days, respectively. Group 1 was considered as control. At 5th, 7th and 10th days after axotomy, 3 rats from each group were killed and the distal stump of sciatic nerve was served for histological assessment.

In the histological examinations of all groups, edema, degraded myelin sheets and some infiltrated mononuclear cells were observed. But administration of high doses of Dex and Thi (groups 4 and 5) alleviated all the above mentioned histological changes. In comparison with control group, the groups received high doses of Dex and Thi showed significant increase in the number of myelinated nerve fibers (p<0.05). Measuring of the cross surface area of the sciatic nerve showed no significant differences. Finally, administration of high dose of Dex was associated with several side effects.

Although these findings indicated the beneficial effects of both Dex and Thi but due to the severe adverse effects of Dex, it is recommended to prescribe Dex for acute and short term cases of nerve injuries, whereas in the case of chronic and long terminflammatory conditions Thi administration may be preferred.