BACKGROUND AND OBJECTIVE: damage to peripheral nerves stimulates a series of morphological and biochemical changes in neurons, which are not concentrated only in the injured region, but are also observed in the cell body of neurons of the spinal cord and in the nerve ganglion. The aim of this study was evaluation of the protective effects of aqueous extract of Achillea millifolium on neuron density of ventral horn of the spinal cord after sciatic nerve compression.

METHODS: In this experimental study, 30 Wistar rats were divided randomly into 5 groups: group I (control), group II (compression), group III (compression + injection of the aqueous extract at a dose of 25 mg/kg), Group IV (compression+injection aqueous extract at a dose of 50 mg/kg), and group V (compression+aqueous plant extract at a dose of 75 mg/kg). Mice were anesthetized and the skin of the right thigh was incised, then the muscles were parted to expose the sciatic nerve. Using forceps, the sciatic nerve cord blood was severely compressed, then the muscles and skin were sutured. Administration of the aqueous extract with group specific doses was performed for three weeks, with one injection per week. 28 days after the surgery, the rats were fixed and the lumbar spinal cord (L4, L5) was removed. Tissue sections were prepared from the spinal cord sample and through toluidine blue staining and photography, the density of alpha motor neurons of the spinal ventral horn was investigated.

FINDINGS: The neuronal density in the compression group compared to the control group showed a significant decrease (943±59 vs. 1620±51.1, p<0.001). Neuronal density in the treatment groups showed a significant increase compared to the compression group. The 75 mg/kg dose showed the highest neuroprotective effect compared to the compression group (1421±139.7 vs. 943±59, p<0.001).

CONCLUSION: The aqueous extract of Achillea millifolium effectively protects motoneurons of the anterior horn of the spinal cord against retrograde injury during sciatic nerve compression