traumatic spinal cord injury ( sci ) often leads to serious neurological sequelae and medical complications .
the secondary damage following sci is induced by multiple pathophysiological mechanisms , including vascular perturbation , metabolic failure , ionic dysregulation , and celluar excitotoxicity7,10 ) .
these mechanisms increase blood - spinal cord barrier permeability , tissue edema , free radical formation , peroxidation of lipid membranes , cytokines release , and inflammation .
a few investigations were introduced in order to minimize secondary damage using electrical stimulation , aminoacids , and drugs3,14,15,18 ) .
electrostimulation of sacral nerve roots is currently being used with promising results as a treatment for a wide spectrum of voiding dysfunctions . also , some investigators reported additional effects of the sacral nerve stimulation such as change of spasticity and spasm , increased motility of intestinal tract and defecation , and improvement of leg motor in experimental and clinical studies3,6,13,17 ) .
prior investigators revealed that one patient with a long history of progressive spinal multiple sclerosis was able to stand and transfer , but not walking , before the sacral nerve stimulation6 ) .
another paraplegic patient was showed improvement of motor power slowly , and after 2 years the patient could stand as confident as before6 ) .
the purpose of this study was to evaluate neuroprotective effect of sacral neuromodulation in rat thoracic spinal cord injury model in histological and functional aspects .
twenty - one sprague dawley of 6 months old female , weighing 200 to 250 gm , were randomly divided into 3 groups : a normal control group ( ctl , n=7 ) , sci with sham stimulation group ( sci , n=7 ) , and sci with electrical stimulation ( sci+es , n=7 ) .
the sci group included rats that were injured with electrodes implanted but did not receive stimulation .
the sci+es group included rats that received electrical stimulation at the s2 or s3 nerve root using needle electrode .
rats in the sci and sci+es groups were kept in separate cages under the same living conditions for a week before receiving scis .
the animals were anesthetized with an intramuscular injection of zoletil 15 mg and xylazine 3 mg . under general anesthesia
after routine disinfection , a surgical incision was made through the skin , subcutaneous tissue , and the t8 - 12 vertebral lamina to the spinal canal ( fig .
severe grade scis were induced in rats using an new york university - multicenter animal spinal cord injury study impactor .
the impact height of 25 mm was considered for severe cord injury based on a prior investigation1 ) . at the s1 - 3 level , a surgical incision was made through the skin , subcutaneous tissue , and the s2 - 3 vertebral lamina ( fig .
needle electrodes ( 0.527 g ) were implanted at bilateral s2 or s3 neural foramina .
wounds were cleaned and sutured with wires inserted through the subcutaneous tissue extruding from the neck .
the sci+es group received electrical stimulation 7 days after sci with the following protocol : stimulation time 30 minutes ; pulse duration , 0.1 ms ; and frequency , 20 hz .
post - injury motor behavior is assessed by the basso , beattie , and bresnahan ( bbb ) locomotor scale method4,5 ) .
the scale ( 0 - 21 ) represents sequential recovery stages and categorizes combinations of rat joint movement , hindlimb movements , stepping , forelimb and hindlimb coordination , trunk position and stability , paw placement , and tail position .
the spinal cord was dissected and embedded in formalin solution , cut into 5 m - thick axial sections , and stained with hematoxylin and eosin ( h&e ) and luxol fast blue to identify structural defects , motor neuron cell injury and myelin loss .
motor neuron cells were counted in the anterior horns of 1 - 2 mm rostral from the epicenter . only complete neuronal cells with a clearly defined cell body and nucleus
twenty - one sprague dawley of 6 months old female , weighing 200 to 250 gm , were randomly divided into 3 groups : a normal control group ( ctl , n=7 ) , sci with sham stimulation group ( sci , n=7 ) , and sci with electrical stimulation ( sci+es , n=7 ) .
the sci group included rats that were injured with electrodes implanted but did not receive stimulation .
the sci+es group included rats that received electrical stimulation at the s2 or s3 nerve root using needle electrode .
rats in the sci and sci+es groups were kept in separate cages under the same living conditions for a week before receiving scis .
the animals were anesthetized with an intramuscular injection of zoletil 15 mg and xylazine 3 mg . under general anesthesia
after routine disinfection , a surgical incision was made through the skin , subcutaneous tissue , and the t8 - 12 vertebral lamina to the spinal canal ( fig .
severe grade scis were induced in rats using an new york university - multicenter animal spinal cord injury study impactor .
the impact height of 25 mm was considered for severe cord injury based on a prior investigation1 ) . at the s1 - 3 level
, a surgical incision was made through the skin , subcutaneous tissue , and the s2 - 3 vertebral lamina ( fig .
needle electrodes ( 0.527 g ) were implanted at bilateral s2 or s3 neural foramina .
wounds were cleaned and sutured with wires inserted through the subcutaneous tissue extruding from the neck .
the sci+es group received electrical stimulation 7 days after sci with the following protocol : stimulation time 30 minutes ; pulse duration , 0.1 ms ; and frequency , 20 hz . epidural low frequency electric stimulation was applied 30 minutes per day for 4 weeks .
post - injury motor behavior is assessed by the basso , beattie , and bresnahan ( bbb ) locomotor scale method4,5 ) .
the scale ( 0 - 21 ) represents sequential recovery stages and categorizes combinations of rat joint movement , hindlimb movements , stepping , forelimb and hindlimb coordination , trunk position and stability , paw placement , and tail position .
the spinal cord was dissected and embedded in formalin solution , cut into 5 m - thick axial sections , and stained with hematoxylin and eosin ( h&e ) and luxol fast blue to identify structural defects , motor neuron cell injury and myelin loss .
motor neuron cells were counted in the anterior horns of 1 - 2 mm rostral from the epicenter . only complete neuronal cells with a clearly defined cell body and nucleus were counted .
the sci group tissue obtained 4 weeks after trauma revealed diffuse hemorrhage , widespread edema , and focal necrosis in both gray - matter and white - matter ( fig .
the traumatized spinal cord was infiltrated with polymorphonuclear leucocytes , erythrocytes , and macrophages in h&e staining .
the number of anterior horn cell was 12.35.7 cells / high power field ( hpf ) in the ctl group , 7.84.9 cells / hpf in the sci group , and 6.95.5 cells / hpf in the sci+es group , respectively . between sci and sci+es group ,
a significant loss of myelin in the white matter was also observed in the sci and sci+es groups compared with the ctl group ( fig .
3 ) . cavitation and demyelinization of the nerve fibers usually has no significant difference between the sci group and the sci+es group . in only 2 specimens of the sci group ,
the open field locomotor scores ( bbb test ) of the corresponding groups are presented in fig .
4 . before the injury , all rats showed normal function on the bbb score .
as demonstrated , all traumatized rats exhibited a severe bbb score at 1 day after sci . at day 1 of sci , the bbb scores of the sci and the es group were 3.01.0 and 2.71.0 , respectively .
they improved significantly at days 3 , 7 , and 14 after sci ( 3 days : 6.41.5 and 6.21.3 , 7 days : 12.50.8 and 13.31.0 , and 14 days : 14.30.5 and 14.50.3 ) .
the animals did improve over time but there was no significant different at any point in time between sci and sci+es groups .
the sci group tissue obtained 4 weeks after trauma revealed diffuse hemorrhage , widespread edema , and focal necrosis in both gray - matter and white - matter ( fig .
the traumatized spinal cord was infiltrated with polymorphonuclear leucocytes , erythrocytes , and macrophages in h&e staining .
the number of anterior horn cell was 12.35.7 cells / high power field ( hpf ) in the ctl group , 7.84.9 cells / hpf in the sci group , and 6.95.5 cells / hpf in the sci+es group , respectively . between sci and sci+es group ,
a significant loss of myelin in the white matter was also observed in the sci and sci+es groups compared with the ctl group ( fig .
3 ) . cavitation and demyelinization of the nerve fibers usually has no significant difference between the sci group and the sci+es group . in only 2 specimens of the sci group ,
the open field locomotor scores ( bbb test ) of the corresponding groups are presented in fig .
4 . before the injury , all rats showed normal function on the bbb score .
as demonstrated , all traumatized rats exhibited a severe bbb score at 1 day after sci . at day 1 of sci , the bbb scores of the sci and the es group were 3.01.0 and 2.71.0 , respectively .
the difference between two groups was not significant . during subsequent scoring periods , bbb scores increased and plateaued around 14 days after sci .
they improved significantly at days 3 , 7 , and 14 after sci ( 3 days : 6.41.5 and 6.21.3 , 7 days : 12.50.8 and 13.31.0 , and 14 days : 14.30.5 and 14.50.3 ) .
the animals did improve over time but there was no significant different at any point in time between sci and sci+es groups .
electrical stimulation has been reported to show neurobiological effects , such as relieving pain in the region of head and face and restoring movement and function in individuals with spinal cord injury6,9 ) .
it has also been indicated that electrical stimulation can directly exert effects on regenerating neural tissues observed under a well - controlled experimental environment9 ) .
several investigators have reported that a low - frequency electrical stimulation is a promise approach to accelerate nerve regeneration after injury2,12 ) .
there are some studies on neuroprotective effects of sacral nerve stimulation in the sci patients2,3,6,11,17 ) .
the additional effect of sacral neuromodulation was improvement of neurogenic bladder , intestinal motility , penile erection , pain discrimination , and motor power of leg6 ) .
however , the current study showed that sacral neuromodulation to rat injured thoracic spinal cord did not prevent sci - induced myelin loss and cavitation .
the number of anterior horn cell of the sci and sci+es groups did not show significant differences .
moreover , no significant differences at any point in time between the sci and sci+es groups were found in terms of locomotor function as assessed by the bbb test .
our hypothesis was that sacral neuromodulation might prevent loss of myelin and promote regeneration of myelinated fiber .
several investigators have reported that a low - frequency electrical stimulation is a promise approach to accelerate nerve regeneration after injury2,12 ) . however
, a high frequency of electrical stimulation may increase failure of nerve regeneration16 ) . hence
, these results can not exclude potential beneficial effects of sacral nerve stimulation in other models of sci with different treatment protocols , the disappointing outcomes in this study were limited by the treatment protocol .
in a rat thoracic spinal cord contusional model , we observed that sacral neuromodulation does not prevent sci - induced myelin loss and cavitation .
further experimental and clinical studies are needed to shed light on the therapeutic potentials of sacral neuromodulation and to determine the most effective protocol of stimulation .
 objectivethe purpose of this study is to evaluate neuroprotective effect of sacral neuromodulation in rat spinal cord injury ( sci ) model in the histological and functional aspects.methodstwenty-one female sprague dawley rats were randomly divided into 3 groups : the normal control group ( ctl , n=7 ) , the sci with sham stimulation group ( sci , n=7 ) , and the sci with electrical stimulation ( sci+es , n=7 ) . 
 spinal cord was injured by dropping an impactor from 25 mm height . 
 sacral nerve electrical stimulation was performed by the following protocol : pulse duration , 0.1 ms ; frequency , 20 hz ; stimulation time , 30 minutes ; and stimulation duration , 4 weeks . 
 both locomotor function and histological examination were evaluated as scheduled.resultsthe number of anterior horn cell was 12.35.7 cells / high power field ( hpf ) in the ctl group , 7.84.9 cells / hpf in the sci group , and 6.95.5 cells / hpf in the sci+es group , respectively . 
 both the sci and the sci+es groups showed severe loss of anterior horn cells and myelin fibers compared with the ctl group . 
 cavitation and demyelinization of the nerve fibers has no significant difference between the sci group and the sci+es group . 
 cavitation of dorsal column was more evident in only two rats of sci group than the sci+es group . 
 the locomotor function of all rats improved over time but there was no significant difference at any point in time between the sci and the sci+es group.conclusionin a rat thoracic spinal cord contusion model , we observed that sacral neuromodulation did not prevent sci - induced myelin loss and apoptosis . 
INTRODUCTION
MATERIALS AND METHODS
Rats and treatment groups
Spinal cord injury and electrical stimulation
Functional and histopathological outcome
RESULTS
Histopathologic examination
Functional outcome
DISCUSSION
CONCLUSION