The Neuroprotective Effect of Nepeta menthoides on Axotomized Dorsal Root Ganglion Sensory Neurons in Neonate Rats

Sensory neurons have critical role in improvement of functional outcome of any neuroprotective strategy. The herbal medicine Nepeta menthoides has been reported to have anti-apoptotic effect on axotomized spinal motoneurons. In the present study, the putative neuroprotective effect of Nepeta menthoides on the axotomized dorsal root ganglion sensory neurons in neonate rats was investigated. In fifteen two-day-old rat neonates, the right sciatic nerve was transected. The animals were subdivided into two experimental groups receiving 250 and 500 mg/kg of Nepeta menthoides and a control group treated with the normal saline as the vehicle for three days following the axotomy. At the fourth day the neonates were sacrificed and the L5 dorsal root ganglions of both sides were dissected and prepared for morphometrical cell count and TUNEL assay. In the control group, four days following axotomy, 38.51% of dorsal root ganglion sensory neurons were lost. Administration of 250 and 500 mg/kg of Nepeta menthoides for three days significantly reduced the cell loss to 24.64% and 21.69%, respectively. The findings of TUNEL assay in control group indicated that axotomy significantly increased the apoptotic index from 3.93% to 10.8%, but in both experimental groups the difference of the reduced percentage of apoptotic cells (the apoptotic index) between intact and axotomized sides was insignificant. Nepeta menthoides through attenuating the apoptotic cell death can induce neuroprotective effect on axotomized dorsal root ganglion sensory neurons.