Abstract Equisetum telmateia (Equisetaceae) seems to have anti inflammatory and antioxidant properties. In the present study, the neuroprotective effects of organic and inorganic silica were investigated on spinal cord alpha motoneuron of rats after injury of sciatic nerve. After highly compression of sciatic nerve in 42 Wistar rats, the injured rats were divided into sham (n= 6) and two experimental groups which each were divided into 3 subgroups (n= 6). The first subgroups received 3, 6 or 9 injections (15 mg/kg/injection, ip) of horse tail extract and the second subgroups received 3, 6 or 9 injections (6 mg/kg/injection, ip) of sodium meta silicate, respectively. The first injection was made after sciatic nerve injury and the others by 72 hours intervals. After a month, the rats were sacrificed and their spinal cord lumber segment sampled, processed for histological preparation and analyzed stereologicaly (the dissector technique) for estimation of numerical density of alpha motoneurons. The results showed significant decrease in the numerical density of alpha motoneurons in shams (p< 0.05) and no significant differences between experimental and control groups. This may suggest the neuroprotective effects of silica on the survival of alpha motoneurons.

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