Early electrical field stimulation prevents the loss of spinal cord anterior horn motoneurons and muscle atrophy following spinal cord injury

Our previous study revealed that early application of electrical field stimulation（EFS） with the anode at the lesion and the cathode distal to the lesion reduced injury potential, inhibited secondary injury and was neuroprotective in the dorsal corticospinal tract after spinal cord injury（SCI）. The objective of this study was to further evaluate the effect of EFS on protection of anterior horn motoneurons and their target musculature after SCI and its mechanism. Rats were randomized into three equal groups. The EFS group received EFS for 30 minutes immediately after injury at T_（10）. SCI group rats were only subjected to SCI and sham group rats were only subjected to laminectomy. Luxol fast blue staining demonstrated that spinal cord tissue in the injury center was better protected; cross-sectional area and perimeter of injured tissue were significantly smaller in the EFS group than in the SCI group. Immunofluorescence and transmission electron microscopy showed that the number of spinal cord anterior horn motoneurons was greater and the number of abnormal neurons reduced in the EFS group compared with the SCI group. Wet weight and cross-sectional area of vastus lateralis muscles were smaller in the SCI group to in the sham group. However, EFS improved muscle atrophy and behavioral examination showed that EFS significantly increased the angle in the inclined plane test and Tarlov＇s motor grading score. The above results confirm that early EFS can effectively impede spinal cord anterior horn motoneuron loss, promote motor function recovery and reduce muscle atrophy in rats after SCI.

Electrical stimulation and denervated muscles after spinal cord injury

Spinal cord injury(SCI)population with injury below T10 or injury to the cauda equina region is characterized by denervated muscles,extensive muscle atrophy,infiltration of intramuscular fat and formation of fibrous tissue.These morphological changes may put individuals with SCI at higher risk for developing other diseases such as various cardiovascular diseases,diabetes,obesity and osteoporosis.Currently,there is no available rehabilitation intervention to rescue the muscles or restore muscle size in SCI individuals with lower motor neuron denervation.We,hereby,performed a review of the available evidence that supports the use of electrical stimulation in restoration of denervated muscle following SCI.Long pulse width stimulation(LPWS)technique is an upcoming method of stimulating denervated muscles.Our primary objective is to explore the best stimulation paradigms(stimulation parameters,stimulation technique and stimulation wave)to achieve restoration of the denervated muscle.Stimulation parameters,such as the pulse duration,need to be 100–1000 times longer than in innervated muscles to achieve desirable excitability and contraction.The use of electrical stimulation in animal and human models induces muscle hypertrophy.Findings in animal models indicate that electrical stimulation,with a combination of exercise and pharmacological interventions,have proven to be effective in improving various aspects like relative muscle weight,muscle cross sectional area,number of myelinated regenerated fibers,and restoring some level of muscle function.Human studies have shown similar outcomes,identifying the use of LPWS as an effective strategy in increasing muscle cross sectional area,the size of muscle fibers,and improving muscle function.Therefore,displaying promise is an effective future stimulation intervention.In summary,LPWS is a novel stimulation technique for denervated muscles in humans with SCI.Successful studies on LPWS of denervated muscles will help in translating this stimulation technique to the clinical level as a rehabilitation intervention after SCI.

Electrical stimulation modulates injury potentials in rats after spinal cord injury

An injury potential is the direct current potential difference between the site of spinal cord injury and the healthy nerves. Its initial amplitude is a significant indicator of the severity of spinal cord injury, and many cations, such as sodium and calcium, account for the major portion of injury potentials. This injury potential, as wel as injury current, can be modulated by direct current field stimulation;however, the appropriate parameters of the electrical field are hard to define. In this paper, injury potential is used as a parameter to adjust the intensity of electrical stimulation. Injury potential could be modulated to slightly above 0 mV （as the anode-centered group） by placing the anodes at the site of the injured spinal cord and the cathodes at the rostral and caudal sections, or around-70 mV, which is resting membrane potential （as the cathode-centered group） by reversing the polarity of electrodes in the anode-centered group. In addition, rats receiving no electrical stimulation were used as the control group. Results showed that the absolute value of the injury potentials acquired after 30 minutes of electrical stimulation was higher than the control group rats and much lower than the initial absolute value, whether the anodes or the cathodes were placed at the site of injury. This phenomenon il ustrates that by changing the polarity of the electrical field, electrical stimulation can effectively modulate the injury potentials in rats after spinal cord injury. This is also beneficial for the spontaneous repair of the cel membrane and the reduction of cation influx.

Epidural electrical stimulation for spinal cord injury

A long-standing goal of spinal cord injury research is to develop effective repair strategies,which can restore motor and sensory functions to near-normal levels.Recent advances in clinical management of spinal cord injury have significantly improved the prognosis,survival rate and quality of life in patients with spinal cord injury.In addition,a significant progress in basic science research has unraveled the underlying cellular and molecular events of spinal cord injury.Such efforts enabled the development of pharmacologic agents,biomaterials and stem-cell based therapy.Despite these efforts,there is still no standard care to regenerate axons or restore function of silent axons in the injured spinal cord.These challenges led to an increased focus on another therapeutic approach,namely neuromodulation.In multiple animal models of spinal cord injury,epidural electrical stimulation of the spinal cord has demonstrated a recovery of motor function.Emerging evidence regarding the efficacy of epidural electrical stimulation has further expanded the potential of epidural electrical stimulation for treating patients with spinal cord injury.However,most clinical studies were conducted on a very small number of patients with a wide range of spinal cord injury.Thus,subsequent studies are essential to evaluate the therapeutic potential of epidural electrical stimulation for spinal cord injury and to optimize stimulation parameters.Here,we discuss cellular and molecular events that continue to damage the injured spinal cord and impede neurological recovery following spinal cord injury.We also discuss and summarize the animal and human studies that evaluated epidural electrical stimulation in spinal cord injury.

Neuromuscular electrical stimulation and testosterone did not influence heterotopic ossification size after spinal cord injury: A case series

Neuromuscular electrical stimulation(NMES) and testosterone replacement therapy(TRT) are effective rehabilitation strategies to attenuate muscle atrophy and evoke hypertrophy in persons with spinal cord injury(SCI). However both interventions might increase heterotopic ossification(HO) size in SCI patients. We present the results of two men with chronic traumatic motor complete SCI who also had pre-existing HO and participated in a study investigating the effects of TRT or TRT plus NMES resistance training(RT) on body composition. The 49-year-old male, Subject A, has unilateral HO in his right thigh. The 31-year-old male, Subject B, has bilateral HO in both thighs. Both participants wore transdermal testosterone patches(4-6 mg/d) daily for 16 wk. Subject A also underwent progressive NMES-RT twice weekly for 16 wk. Magnetic resonance imaging scans were acquired prior to and post intervention. Cross-sectional areas(CSA) of thewhole thigh and knee extensor skeletal muscles, femoral bone, and HO were measured. In Subject A(NMES-RT + TRT), the whole thigh skeletal muscle CSA increased by 10%, the knee extensor CSA increased by 17%, and the HO + femoral bone CSA did not change. In Subject B(TRT), the whole thigh skeletal muscle CSA increased by 13% in the right thigh and 6% in the left thigh. The knee extensor CSA increased by 7% in the right thigh and did not change in the left thigh. The femoral bone and HO CSAs in both thighs did not change. Both the TRT and NMES-RT + TRT protocols evoked muscle hypertrophy without stimulating the growth of preexisting HO.

Rebuilding motor function of the spinal cord based on functional electrical stimulation

Rebuilding the damaged motor function caused by spinal cord injury is one of the most serious challenges in clinical neuroscience.The function of the neural pathway under the damaged sites can be rebuilt using functional electrical stimulation technology.In this study,the locations of motor function sites in the lumbosacral spinal cord were determined with functional electrical stimulation technology.A three-dimensional map of the lumbosacral spinal cord comprising the relationship between the motor function sites and the corresponding muscle was drawn.Based on the individual experimental parameters and normalized coordinates of the motor function sites,the motor function sites that control a certain muscle were calculated.Phasing pulse sequences were delivered to the determined motor function sites in the spinal cord and hip extension,hip flexion,ankle plantarflexion,and ankle dorsiflexion movements were successfully achieved.The results show that the map of the spinal cord motor function sites was valid.This map can provide guidance for the selection of electrical stimulation sites during the rebuilding of motor function after spinal cord injury.

Safety and effectiveness of electromyography-induced rehabilitation treatment after epidural electrical stimulation for spinal cord injury:study protocol for a prospective,randomized,controlled trial

Epidural electrical stimulation is a new treatment method for spinal cord injury(SCI).Its efficacy and safety have previously been reported.Rehabilitation treatment after epidural electrical stimulation is important to ensure and improve the postoperative efficacy of epidural electrical stimulation in patients with SCI.Considering that electromyography(EMG)-induced rehabilitation treatment can accurately match the muscle contraction of patients with SCI,we designed a study protocol for a prospective,randomized controlled trial.In this trial,on the premise of adjusting the spinal cord electrical stimulator to obtain the maximum EMG signal of the target muscle,patients with SCI receiving epidural electrical stimulation will undergo EMG-induced rehabilitation treatment.Recovery of muscle strength of key muscles,quality of life,safety and therapeutic effects will be monitored.Twenty patients with SCI who are scheduled to undergo epidural electrical stimulation in Shanghai Ruijin Rehabilitation Hospital will be randomly divided into two groups with 10 patients per group.The control group will receive conventional rehabilitation treatment.The EMG-induced rehabilitation group will receive EMG-induced rehabilitation treatment of the target muscles of the upper and lower limbs based on conventional rehabilitation treatment.After rehabilitation treatment,follow up for all patients will occur at 2 weeks and 1,3 and 6 months.The primary outcome measure of this trial will be evaluation of target muscle recovery using the Manual Muscle Testing grading scale.Secondary outcome measures will include modified Barthel Index scores,integrated EMG values,the visual analogue scale,Spinal Cord Independence Measure scores,and modified Ashworth scale scores.The safety indicator will be the incidence of adverse events.This trial will collect data regarding the therapeutic effects of EMG-induced rehabilitation in patients with SCI receiving epidural electrical stimulation for 6 months after rehabilitation treatment.Findings from this trial will help develop rehabilitation methods in patients with SCI after epidural electrical stimulation.This study protocol was approved by Ethics Committee of Shanghai Ruijin Rehabilitation Hospital(Approval No.RKIRB2022-12)on February 15,2022 and was registered with Chinese Clinical Trial Registry(registration number:ChiCTR2200061674;date:June 30,2022).Study protocol version:1.0.

Combination of epidural electrical stimulation with ex vivo triple gene therapy for spinal cord injury:a proof of principle study

Despite emerging contemporary biotechnological methods such as gene-and stem cell-based therapy,there are no clinically established therapeutic strategies for neural regeneration after spinal cord injury.Our previous studies have demonstrated that transplantation of genetically engineered human umbilical cord blood mononuclear cells producing three recombinant therapeutic molecules,including vascular endothelial growth factor(VEGF),glial cell-line derived neurotrophic factor(GDNF),and neural cell adhesion molecule(NCAM)can improve morpho-functional recovery of injured spinal cord in rats and mini-pigs.To investigate the efficacy of human umbilical cord blood mononuclear cells-mediated triple-gene therapy combined with epidural electrical stimulation in the treatment of spinal cord injury,in this study,rats with moderate spinal cord contusion injury were intrathecally infused with human umbilical cord blood mononuclear cells expressing recombinant genes VEGF165,GDNF,NCAM1 at 4 hours after spinal cord injury.Three days after injury,epidural stimulations were given simultaneously above the lesion site at C5(to stimulate the cervical network related to forelimb functions)and below the lesion site at L2(to activate the central pattern generators)every other day for 4 weeks.Rats subjected to the combined treatment showed a limited functional improvement of the knee joint,high preservation of muscle fiber area in tibialis anterior muscle and increased H/M ratio in gastrocnemius muscle 30 days after spinal cord injury.However,beneficial cellular outcomes such as reduced apoptosis and increased sparing of the gray and white matters,and enhanced expression of heat shock and synaptic proteins were found in rats with spinal cord injury subjected to the combined epidural electrical stimulation with gene therapy.This study presents the first proof of principle study of combination of the multisite epidural electrical stimulation with ex vivo triple gene therapy(VEGF,GDNF and NCAM)for treatment of spinal cord injury in rat models.The animal protocols were approved by the Kazan State Medical University Animal Care and Use Committee(approval No.2.20.02.18)on February 20,2018.

Pulsed electrical stimulation protects neurons in the dorsal root and anterior horn of the spinal cord after peripheral nerve injury

Most studies on peripheral nerve injury have focused on repair at the site of injury, but very few have examined the effects of repair strategies on the more proximal neuronal cell bodies. In this study, an approximately 10-mm-long nerve segment from the ischial tuberosity in the rat was transected and its proximal and distal ends were inverted and sutured. The spinal cord was subjected to pulsed electrical stimulation at T10 and L3, at a current of 6.5 m A and a stimulation frequency of 15 Hz, 15 minutes per session, twice a day for 56 days. After pulsed electrical stimulation, the number of neurons in the dorsal root ganglion and anterior horn was increased in rats with sciatic nerve injury. The number of myelinated nerve fibers was increased in the sciatic nerve. The ultrastructure of neurons in the dorsal root ganglion and spinal cord was noticeably improved. Conduction velocity of the sciatic nerve was also increased. These results show that pulsed electrical stimulation protects sensory neurons in the dorsal root ganglia as well as motor neurons in the anterior horn of the spinal cord after peripheral nerve injury, and that it promotes the regeneration of peripheral nerve fibers.

Electrical stimulation of cortical neurons promotes oligodendrocyte development and remyelination in the injured spinal cord

Background and early studies： Endogenous tri-potential neural stem cells （NSCs） exist in the adult mammalian central nervous system （CNS）. In the spinal cord, NSCs distribute throughout the entire cord, but exist predominately in white matter tracts. The phenotypic fate of these cells in white matter is glial, largely oligodendrocyte, but not neuronal.

Tail nerve electrical stimulation-induced walking training promotes restoration of locomotion and electrophysiology in rats with chronic spinal cord injury

Functional recovery is the final goal in the treatment of spinal cord injury. However, to date, few treatment strategies have demonstrated significant locomotor improvement in animal experiments. By using tail nerve electrical stimulation (TANES) as an open-field locomotor training method combined with glial scar ablation and cell transplantation, we have successfully promoted locomotor recovery in rats with chronic spinal cord contusion injury. The purpose of the present study is to further investigate the mechanism of TANES and its effect on electrophysiology. Spinal cord segment T10 of female, adult Long-Evans rats was contused using the NYU impactor device with 25 mm height setting. After injury, rats were randomly divided into three groups. Group I was used as a control without any treatment, group II and group III were subjected to basic treatment including glial scar ablation and transplantation of olfactory lamina propria 6 weeks after injury, and group III received TANES-induced open-field locomotor training weekly after basic treatment. All animals were allowed to survive 22 weeks, except some rats which were transected. Basso, Beattie, and Bresnahan (BBB) open-field locomotor rating scale, horizontal ladder rung walking test, and electrophysiological tests were used to assess the restoration of functional behavior and conduction. Results showed that TANES significantly improves locomotor recovery and spinal cord conduction, reflex, as well as significantly reduces the occurrence of autophagia. Additionally, after transection, trained rats still maintained higher BBB score than that of control rats. This may be related to the activity-dependent plasticity promoted by TANES-induced locomotor training.

Passive activity enhances residual control ability in patients with complete spinal cord injury

Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface electromyography.In this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord injury.Eleven patients with chronic complete thoracic spinal cord injury were recruited.Surface electromyography data from eight major leg muscles were acquired and compared before and after the passive activity protocol.The results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of activation.Although the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically significant.These findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.

Combinatorial therapies for spinal cord injury repair

Spinal cord injuries have profound detrimental effects on individuals, regardless of whether they are caused by trauma or non-traumatic events. The compromised regeneration of the spinal cord is primarily attributed to damaged neurons, inhibitory molecules, dysfunctional immune response, and glial scarring. Unfortunately, currently, there are no effective treatments available that can fully repair the spinal cord and improve functional outcomes. Nevertheless, numerous pre-clinical approaches have been studied for spinal cord injury recovery, including using biomaterials, cells, drugs, or technological-based strategies. Combinatorial treatments, which target various aspects of spinal cord injury pathophysiology, have been extensively tested in the last decade. These approaches aim to synergistically enhance repair processes by addressing various obstacles faced during spinal cord regeneration. Thus, this review intends to provide scientists and clinicians with an overview of pre-clinical combinatorial approaches that have been developed toward the solution of spinal cord regeneration as well as update the current knowledge about spinal cord injury pathophysiology with an emphasis on the current clinical management.

Basic mechanisms of peripheral nerve injury and treatment via electrical stimulation

Previous studies on the mechanisms of peripheral nerve injury(PNI)have mainly focused on the pathophysiological changes within a single injury site.However,recent studies have indicated that within the central nervous system,PNI can lead to changes in both injury sites and target organs at the cellular and molecular levels.Therefore,the basic mechanisms of PNI have not been comprehensively understood.Although electrical stimulation was found to promote axonal regeneration and functional rehabilitation after PNI,as well as to alleviate neuropathic pain,the specific mechanisms of successful PNI treatment are unclear.We summarize and discuss the basic mechanisms of PNI and of treatment via electrical stimulation.After PNI,activity in the central nervous system(spinal cord)is altered,which can limit regeneration of the damaged nerve.For example,cell apoptosis and synaptic stripping in the anterior horn of the spinal cord can reduce the speed of nerve regeneration.The pathological changes in the posterior horn of the spinal cord can modulate sensory abnormalities after PNI.This can be observed in cases of ectopic discharge of the dorsal root ganglion leading to increased pain signal transmission.The injured site of the peripheral nerve is also an important factor affecting post-PNI repair.After PNI,the proximal end of the injured site sends out axial buds to innervate both the skin and muscle at the injury site.A slow speed of axon regeneration leads to low nerve regeneration.Therefore,it can take a long time for the proximal nerve to reinnervate the skin and muscle at the injured site.From the perspective of target organs,long-term denervation can cause atrophy of the corresponding skeletal muscle,which leads to abnormal sensory perception and hyperalgesia,and finally,the loss of target organ function.The mechanisms underlying the use of electrical stimulation to treat PNI include the inhibition of synaptic stripping,addressing the excessive excitability of the dorsal root ganglion,alleviating neuropathic pain,improving neurological function,and accelerating nerve regeneration.Electrical stimulation of target organs can reduce the atrophy of denervated skeletal muscle and promote the recovery of sensory function.Findings from the included studies confirm that after PNI,a series of physiological and pathological changes occur in the spinal cord,injury site,and target organs,leading to dysfunction.Electrical stimulation may address the pathophysiological changes mentioned above,thus promoting nerve regeneration and ameliorating dysfunction.

Long-term anodal block stimulation at sacral anterior roots promoted recovery of neurogenic bladder function in a rabbit model of complete spinal cord injury

A complete spinal cord injury model was established in experimental rabbits using the spinal cord clip compression method. Urodynamic examination was performed 2 weeks later to determine neurogenic bladder status. The rabbits were treated with anodal block stimulation at sacral anterior roots for 4 weeks. Electrical stimulation of sacral anterior roots improved urodynamic parameters of neurogenic bladder in rabbit models of complete spinal cord injury, effectively promoted urinary function, and relieved urinary retention. Immunohistochemistry results showed that a balance was achieved among expression of muscarinic receptor subunits M2, M3, ATP-gated ion channel P2X3 receptors, and 132-adrenergic receptor, and nerve growth factor expression decreased. These results suggested that long-term sacral anterior root stimulation of anodal block could＇be used to treat neurogenic bladder in a rabbit model of complete spinal cord injury.

Prolonged electrical stimulation causes no damage to sacral nerve roots in rabbits

Previous studies have shown that, anode block electrical stimulation of the sacral nerve root can produce physiological urination and reconstruct urinary bladder function in rabbits. However, whether long-term anode block electrical stimulation causes damage to the sacral nerve root re- mains unclear, and needs further investigation. In this study, a complete spinal cord injury model was established in New Zealand white rabbits through T9_10 segment transection. Rabbits were given continuous electrical stimulation for a short period and then chronic stimulation for a longer period. Results showed that compared with normal rabbits, the structure of nerve cells in the anterior sacral nerve roots was unchanged in spinal cord injury rabbits after electrical stimu- lation. There was no significant difference in the expression of apoptosis-related proteins such as Bax, Caspase-3, and Bcl-2. Experimental findings indicate that neurons in the rabbit sacral nerve roots tolerate electrical stimulation, even after long-term anode block electrical stimulation.

High-frequency spinal cord stimulation produces longlasting analgesic effects by restoring lysosomal function and autophagic flux in the spinal dorsal horn

High-frequency spinal cord stimulation(HF-SCS) has been established as an effective therapy for neuropathic pain. However, the analgesic mechanisms involved in HF-SCS remain to be clarified. In our study, adult rat neuropathic pain was induced by spinal nerve ligation. Two days after modeling, the rats were subjected to 4 hours of HF-SCS(motor threshold 50%, frequency 10,000 Hz, and pulse width 0.024 ms) in the dorsal horn of the spinal cord. The results revealed that the tactile allodynia of spinal nerve-injured rats was markedly alleviated by HFSCS, and the effects were sustained for 3 hours after the stimulation had ceased. HF-SCS restored lysosomal function, increased the levels of lysosome-associated membrane protein 2(LAMP2) and the mature form of cathepsin D(matu-CTSD), and alleviated the abnormally elevated levels of microtubule-associated protein 1 A/B-light chain 3(LC3)-II and sequestosome 1(P62) in spinal nerve-injured rats. HF-SCS also mostly restored the immunoreactivity of LAMP2, which was localized in neurons in the superficial layers of the spinal dorsal horn in spinal nerve-injured rats. In addition, intraperitoneal administration of 15 mg/kg chloroquine for 60 minutes reversed the expression of the aforementioned proteins and shortened the timing of the analgesic effects of HF-SCS. These findings suggest that HF-SCS may exhibit longlasting analgesic effects on neuropathic pain in rats through improving lysosomal dysfunction and alleviating autophagic flux. This study was approved by the Laboratory Animal Ethics Committee of China Medical University, Shenyang, China(approval No. 2017 PS196 K) on March 1, 2017.

Methylprednisolone and tetrandrine in combination with direct current electrical field for treating acute spinal cord injury

BACKGROUND： The direct current electrical field can effectively promote the regeneration of the spinal cord; moreover, methylprednisolone （MP） can relieve secondary edema after spinal cord injury. Tetrandrine （Tet） is an effective component of hanfangji and can protect the effect of spinal cord and axis-cylinder. Whether direct current electrical field combining with MP or Tet has synergic or strengthening effect on treating complete spinal cord injury or not should be studied further. OBJECTIVE：To study the effect of direct current electrical field assisted by MP and Tet on treating spinal cord injury. DESIGN： Randomized controlled animal study. SETTING： People＇s Hospital of Hainan Province. MATERIALS： A total of 45 healthy hybrid dogs, of both genders, weighing 10 - 12 kg, aged 1.5 - 2 years, were provided by Animal Center of Hainan Province. Somatosensory evoked potential meter （DANTEC Company）, IBAS-2.0 imaging analysis meter （Germany）, and self-made electronic stimulator. METHODS： The experiment was carried out in Hainan People＇s Hospital from May 2001 to June 2004. All experimental dogs were randomly divided into 4 groups： control group （n =9）, electrostimulating group （n =12）, MP ＋ electrostimulating group （n =12） and Tet ＋ electrostimulating group （n =12）. ① After anesthesia, Allen WD method was used to induce complete spinal cord injury. The metal bar, which was 10 cm in height fell freely and vertically hit the spinal cord to provide a complete spinal cord injury. Dogs in control group and electrostimulating group were implanted electrical stimulators 6 hours after spinal cord injury （no electricity in control group）; dogs in MP ＋ electrostimulating group were injected 30 mg/kg MP for 15 minutes at 2 hours after spinal cord injury and electrical stimulators implanted at 6 hours after injury; dogs in Tet ＋ electrostimulating group were intravenously injected with 7.5 mg/kg Tet at 2 hours after spinal cord injury and electrical stimulators implanted at 6 hours after injury; and then, 7.5 mg/kg Tet injected at days 2 and 3 after injury. ② Specimens were taken from control group from three dogs of every month; from the injured segments of spinal cords at 1 month, 2 months and 3 months; and from electrostimulating group, MP ＋ electrostimulating group and Tet ＋ electrostimulating group of 4 dogs for histological examinations. ③Detection of neurological function： Neurological function was evaluated with the functional 10 grading system. The scores ranged from 0 to 10 （0： complete paraplegia; 10： normality）. ④Detection of cortical somatosensory evoked potential （CSEP）： According to the scheme formulated by the International Electroencephalographical Association, the patterns of the fundamental waves were P1 - N1 - P1 waves. The latency of the P1 wave and the amplitude of P1 -N1 waves were mainly observed individually at 1, 2 and 3 months after the injury. ⑤Histological detection： All spinal cord specimens of the injuried segment were harvested at 1, 2 and 3 months after injury. They were stained with hematoxylin and Nissl staining methods, and then were observed under an optical microscope, and the neurons were counted. The sectional areas of the neurons and the density of the Nissl bodies were measured by a system image pattern analysis （IBAS-2.0, Germany）. MAIN OUTCOME MEASURES： The neurological function, cortical somatosensory evoked potential, neuronal amount, sectional area of neurons and Nissl body density at 1 to 3 months after injury. RESULTS： All 45 experimental dogs were involved in the final analysis. ① Detection of neurological function： One month later, the dogs in MP ＋ electrostimulating group could walk, but the dogs in electrostimulating group and Tet ＋ electrostimulating group could stand. Two months after injury, the dogs in MP ＋ electrostimulating group almost recovered to normal, but the dogs in electrostimulating group could walk and those in Tet ＋ electrostimulating group could run. Those in control group had no parent recovery.②Detection of P1 latency and P1 - N1 amplitude： Changes of P1 latency in control group were long and P1 -N1 amplitude was very low at 1 month later. Compared to electrostimulating group, MP ＋ electrostimulating group and Tet ＋ electrostimulating group, there were significant differences （P 〈 0.05）. P1 latency was manifestly shortened and amplitude were raised in electrostimulating group, MP ＋ electrostimulating group and Tet ＋ electrostimulating group. Those in MP ＋ electrostimulating group and Tet ＋ electrostimulating group were superior to those in electrostimulating group and there were significant differences （P 〈 0.05）. ③Sectional areas of neurons and Nissl body density： At 1 - 3 months after injury, sectional areas of neurons were larger in electrostimulating group [（170.14 ±7.45）, （209.60 ±14.80）, （312.47±12.63） μm^2], MP ＋ electrostimulating group [（282.18±15.25）, （418.18±16.27）, （515.25±15.10） μm^2] and Tet ＋ electrostimulating group [（231.81±7.38）, （322.67±8.45）, （386.82±10.42） μm^2] control group[（98.12±4.93）, （113.50±6.74）, （122.59±8.03） μm^2, P 〈 0.05]; especially, sectional area was the largest in MP ＋ electrostimulating group. At 1 - 3 months after injury, Nissl body density was more in electrostimulating group （ 170.14 ±7.45, 209.60 ± 14.80, 312.47 ± 12.63 ）, MP ＋ electrostimulating group （282.18±15.25, 418.18±16.27, 515.25±15.10） and Tet ＋ electrostimulating group （231.81±7.38, 322.67±8.45, 386.82±10.42） than control group （98.12±4.93, 113.50±6.74, 122.59±8.03, P 〈 0.05）; especially, Nissl body density was the most in MP ＋ electrostimulating group. CONCLUSION： The direct current electrical field can effectively promote spinal cord regeneration. The combination of direct current electrical field with large dose MP or Tet has synergistic effects for treating spinal cord injury. The curative effects of direct current electrical field with large dose MP are much better than those with Tet.

Electric stimulation at sciatic nerve evokes long-term potentiation of cornu dorsale medullae spinalis field potential in rats at various developmental phases

BACKGROUND： Long-term potentiation of cornu dorsale medullae spinalis field potential in adult rats has already been reported; however, there is lack of correlated researches on naenonate, infant and adult rats which have different responses to pain conduction information.OBJECTIVE： To observe the various effects of electric stimulation at sciatic nerve on long-term potentiation of evoked field potential at superficial layer of cornu dorsale medullae spinalis of rats at various developmental phases and analyze manifestations of pain conduction information at superficial layers （ Ⅰ - Ⅱ）of cornu dorsale medullae spinalis in immature rats.DESIGN： Grouping controlled study.SETTING： Department of Physiology, Medical College of Wuhan University.MATERIALS： The experiment was carried out in the Laboratory of Physiology （provincial laboratory）,Medical College of Wuhan University from March 2006 to May 2007. A total of 27 healthy male Sprague-Dawley （SD） rats, 17- 90 days old, SPF grade, weighing 41 -200 g, were provided by Experimental Animal Center, Medical College of Wuhan University.METHODS： Based on their birthdays, rats were divided into naenonate group （17 - 20 days old, weighing 41-52 g, n =10）, infant group （35 - 50 days old, weighing 87 - 125 g, n =10） and adult group （60 - 90 days old, weighing 180 -200 g, n =7）. Left sciatic nerve was separated and stimulated with single square wave （15 V, 0.5 ms）. Meanwhile, evoked field potential was recorded at superficial layers of lateral T13 - L1 cornu dorsale medullae spinalis and then stimulated with high-frequent and high-intensive tetanizing current （30 -40 V, 0.5 ms, 100 Hz, 1s per bundle, 10s in bundle interval） four times. After the operation, onset of long-term potentiation was observed; meanwhile, amplitude changes and latency of field potential were analyzed.MAIN OUTCOME MEASURES： Amplitude and latency changes of field potential at superficial layers of cornu dorsale medullae spinalis of rats in the three groups.RESULTS： A total of 27 accepted rats were involved in the final analysis. ① Amplitude changes： Electric stimulation at sciatic nerve with high-frequent and high-intensive tetanizing current could induce evoked field potential at superficial layers （Ⅰ-Ⅱ ） of cornu dorsale medullae spinalis in the three groups.Long-term potentiation in the naenonate group manifested that amplitude of A-kind never fiber was raised and there was significant difference （P〈0.05）. In addition, average amplitude was increased and there was obviously significant difference （P〈0.01）. Long-term potentiation in the infant group manifested that amplitude of C-kind never fiber was raised and there was significant difference （P〈0.01）; while, long-term potentiation in the adult group manifested that amplitude of C-kind never fiber was raised and there was significant difference （P〈0.01）. Otherwise, latencies in the three groups were all shortened. ② Latency changes： Average latency of A-kind nerve fiber in the naenonate group was shortened and there was significant difference （P〈0.01）; in addition, evoked potential of C-kind nerve fiber was low and latency was immovable. There was no significant difference before and after high-frequent and high-intensive electric stimulation （P〉0.05）. Average latency of C-kind nerve fiber in the infant group was shortened and there was significant difference （P〈0.01）; in addition, evoked potential of A-kind nerve fiber was stable and latency was immovable. There was no significant difference before and after high-frequent and high-intensive electric stimulation （P〉0.05）. Average latency of C-kind nerve fiber in the adult group was shortened and there was significant difference （P〈0.01）; in addition, evoked potential of A-kind nerve fiber was stable and latency was immovable. There was no significant difference before and after high-frequent and high-intensive electric stimulation.CONCLUSION： Evoked field potential at superficial layer of comu dorsale medullae spinalis can be recorded through electric stimulation at sciatic nerve. Single stimulation and tetanizing electric stimulation can cause different characteristics of evoked field potential in rats at various developmental phases.Superficial layer of cornu dorsale medullae spinalis of naenonate rats is mainly caused by A-kind nerve fiber which participants in pain conduction and formation of pain sensitivity; however, that of infant and adult rats mainly depends on C-kind nerve fiber.

Electrical stimulation of dog pudendal nerve regulates the excitatory pudendal-to-bladder reflex

Pudendal nerve plays an important role in urine storage and voiding.Our hypothesis is that a neuroprosthetic device placed in the pudendal nerve trunk can modulate bladder function after suprasacral spinal cord injury.We had confirmed the inhibitory pudendal-to-bladder reflex by stimulating either the branch or the trunk of the pudendal nerve.This study explored the excitatory pudendal-to-bladder reflex in beagle dogs,with intact or injured spinal cord,by electrical stimulation of the pudendal nerve trunk.The optimal stimulation frequency was approximately 15–25 Hz.This excitatory effect was dependent to some extent on the bladder volume.We conclude that stimulation of the pudendal nerve trunk is a promising method to modulate bladder function.