Clinical trials have demonstrated that kilohertz-frequency transcutaneous spinal cord stimulation (TSCS) can be used to facilitate the recovery of sensory-motor function for patients with spinal cord injury, whereas the neural mechanism of TSCS is still undetermined so that the choice of stimulation parameters is largely dependent on the clinical experience. In this paper, a finite element model of transcutaneous spinal cord stimulation was used to calculate the electric field distribution of human spinal cord segments T ₁₂ to L ₂, whereas the activation thresholds of spinal fibers were determined by using a double-cable neuron model. Then the variation of activation thresholds was obtained by varying the carrier waveform, the interphase delay, the modulating frequency, and the modulating pulse width. Compared with the sinusoidal carrier, the usage of square carrier could significantly reduce the activation threshold of dorsal root (DR) fibers. Moreover, the variation of activation thresholds was no more than 1 V due to the varied modulating frequency and decreases with the increased modulating pulse width. For a square carrier at 10 kHz modulated by rectangular pulse with the frequency of 50 Hz and the pulse width of 1 ms, the lowest activation thresholds of DR fibers and dorsal column fibers were 27.6 V and 55.8 V, respectively. An interphase delay of 5 μs was able to reduce the activation thresholds of the DR fibers to 20.1 V. The simulation results can lay a theoretical foundation on the selection of TSCS parameters in clinical trials.
Humans ; Spinal Cord Stimulation/methods* ; Nerve Fibers/physiology* ; Finite Element Analysis ; Spinal Cord/physiology* ; Computer Simulation ; Spinal Cord Injuries/physiopathology* ; Lumbosacral Region ; Lumbar Vertebrae ; Transcutaneous Electric Nerve Stimulation/methods* ; Models, Neurological

OBJECTIVETo study the effects of sacral nerve root electrostimulation (SNS) on the colon function and its mechanisms in rats with spinal cord injury (SCI).

METHODSOne hundred and four Wistar rats were divided into three groups: A, B and C. A group ( n = 24) was divided into three subgroups (n = 8) for studying the bioelectricity: Normal group (NG), SCI group (SCI) and SCI group with SNS(SNS); B group( n = 24) was divided into three subgroups( n = 8) for studying the colon motility: NG, SCI and SNS. C group( n = 56) were divided into three groups for studying the change of morphology and neurotransmitters(SP and VIP): NG (n = 8), SCI (n = 24), and SNS (n = 24) . In SCI and SNS, included of three subgroups: 24, 48, 72 h after spinal cord injury (n = 8).

RESULTSIn SCI group, the activity of bioelectricity in proximal and distal colon was reduced; the colon motility was lessened, and colon mucosa appeared different degree of damage; cell-cell connections between intestinal epithelial cells were destroyed. The expressions of substance P(SP) and vasoactive intestinal peptide (VIP) in colon were decreased obviously. SNS was found to activate the bioelectricity, promote the colon motility, improve the intestinal mucosal, and increase the expressions of SP and VIP. Conclusion: SNS can activate the peristalsis, rehabilitate the motility of denervated colon, protection of the intestinal mechanical barrier between intestinal epithelial cells and tight junction, rebuild the colon function through activating the bioelectricity and increase the expressions of SP and VIP.

Animals ; Colon ; physiopathology ; Electric Stimulation Therapy ; Epithelial Cells ; drug effects ; Intestinal Mucosa ; drug effects ; Lumbosacral Region ; innervation ; Neurotransmitter Agents ; metabolism ; Rats ; Rats, Wistar ; Spinal Cord Injuries ; therapy ; Substance P ; metabolism ; Vasoactive Intestinal Peptide ; metabolism

OBJECTIVETo investigate the effect of electrical stimulation to sacral spinal nerve 3 (S₃ stimulation) on gastrointestinal dysfunction after spinal cord injury (SCI).

METHODSSix rabbits were taken as normal controls to record their gastrointestinal multipoint biological discharge, colon pressure and rectoanal inhibitory reflex. Electrodes were implanted into S₃ in another 18 rabbits. Then the model of SCI was conducted following Fehling's method: the rabbit S₃ was clamped to induce transverse injury, which was claimed by both somatosensory evoked potential and motion evoked potential. Two hours after SCI, S₃ stimulation was conducted. The 18 rabbits were subdivided into 3 groups to respectively record their gastrointestinal electric activities (n=6), colon pressure (n=6), and rectum pressure (n=6). Firstly the wave frequency was fixed at 15 Hz and pulse width at 400 μs and three stimulus intensities (6 V, 8 V, 10 V) were tested. Then the voltage was fixed at 6 V and the pulse width changed from 200 μs, 400 μs to 600 μs. The response was recorded and analyzed. The condition of defecation was also investigated.

RESULTSAfter SCI, the mainly demonstrated change was dyskinesia of the single haustrum and distal colon. The rectoanal inhibitory reflex almost disappeared. S₃ stimulation partly recovered the intestinal movement after denervation, promoting defecation. The proper stimulus parameters were 15 Hz, 400 μs, 6 V, 10 s with 20 s intervals and 10 min with 10 min intervals, total 2 h.

CONCLUSIONS₃ stimulation is able to restore the intestinal movement after denervation (especially single haustrum and distal colon), which promotes defecation.

Animals ; Disease Models, Animal ; Electric Stimulation ; Electrodes, Implanted ; Evoked Potentials, Motor ; physiology ; Evoked Potentials, Somatosensory ; physiology ; Gastrointestinal Tract ; physiopathology ; Rabbits ; Sacrum ; innervation ; Spinal Cord Injuries ; physiopathology

OBJECTIVETo study the protective effects of sacral nerve root electrostimulation on intestinal mechanical barrier in rats with spinal cord injury (SCI).

METHODSFifty six Wistar rats were divided into normal group, SCI control group and SCI group with sacral nerve root electrostimulation (8 rats in each subgroup at 24, 48, 72 h after spinal cord injury). The following experiments were performed respectively in rats from the 3 groups: bacteria culture from intestinal mesentery lymph nodes, liver, spleen, intestinal morphology observation and detection the protein expression level of ZO-1.

RESULTSThe intestinal mucosa appeared different degree of damage in SCI control group; cell-cell connections between intestinal epithelial cells were destroyed; Endotoxin levels in blood and the number of bacterial translocation increased obviously. Sacral nerve stimulation was found toimprove the intestinal mucosal, reduce the endotoxin content in the blood to normal level and the decrease the incidences of bacterial translocation of the gut origin. The expression of tight junction protein ZO-1 of rat intestinal tissue had no statistical differences among the 3 groups. On the other hand, the distribution of tight junction protein ZO-1 appeared different degrees of scattered and irregular in the control group while that in the experimental group appeared different degree of improvement as determined by the immunohistochemistry of rat intestinal tissue.

CONCLUSIONsacral nerve root electrostimulation can rehabilitate the peristalsis of denervated colon, promote defeacation and decrease bacterial amount, protection of the intestinal mechanical barrier between intestinal epithelial cells and tight junction, reducing the endotoxin content in the blood and suppressing bacterial translocation from the gut.

Animals ; Bacterial Translocation ; Electric Stimulation Therapy ; Endotoxins ; blood ; Epithelial Cells ; cytology ; Intestinal Mucosa ; physiology ; Peristalsis ; Rats ; Rats, Wistar ; Spinal Cord ; Spinal Cord Injuries ; physiopathology ; Zonula Occludens-1 Protein ; metabolism

Endogenous electric fields (EFs) have been detected at wounds and damaged tissues. The potential roles of EFs in tissue repair and regeneration have been an intriguing topic for centuries. Recent researches have provided significant insights into how naturally occurring EFs may participate in the control of tissue repair and regeneration. Applied EFs equivalent to the size of fields measured in vivo direct cell migration, cell proliferation and nerve sprouting at wounds. More remarkably, physiological EFs are a guidance cue that directs cell migration which overrides other well accepted directional signals including initial injury stimulation, wound void, contact inhibition release, population pressure and chemotaxis. EFs activate many intracellular signaling pathways in a directional manner. Modulation of endogenous wound EFs affects epithelial cell migration, cell proliferation, and nerve growth at cornea wounds in vivo. Electric stimulation is being tested clinically for the treatments of bone fracture, wound healing and spinal cord injury. EFs thus may represent a novel type of signaling paradigm in tissue repair and regeneration. Combination of the electric stimulation and other well understood biochemical regulatory mechanisms may offer powerful and effective therapies for tissue repair and regeneration. This review introduces experimental evidence for the existence of endogenous EFs and discusses their roles in tissue repair and regeneration.
Cell Division ; Cell Movement ; Cell Proliferation ; Electric Stimulation ; Electromagnetic Fields ; Humans ; Neurons ; physiology ; Regeneration ; Wound Healing ; Wounds and Injuries ; physiopathology

OBJECTIVETo evaluate the effect of radiofrequency of different temperatures and durations on sciatic nerve motor conduction velocity (MCV).

METHODSThe bilateral sciatic nerve of 70 adult SD rats was dissected and exposed to radiofrequency ablation of different temperatures (30, 50, 55, 60, and 70 degrees C) and durations. The nerves were also exposed to increasing ablation temperatures from 30 degrees C to 50 degrees C with an increment of 5 degrees C (60 s at each temperature), and the changes in the MCV parameters were observed.

RESULTSThe MCV parameters of rat sciatic nerve underwent significant changes following the radiofrequency exposures (P<0.05) except for the exposure at 55 degrees celsius; for 10 s. Below the temperature of 55 degrees celsius;, the MCV showed no obvious correlation to the exposure time for the group. For the nerves exposed to radiofrequency of 55 degrees celsius;, the latency was not correlated to the exposure time within 30 s, and data could be obtained from 55 s group; with these exceptions, the latency was found to positively while the negative phase wave inversely correlated to the exposure time. With fixed exposure time of 60 s, the MCV parameters were positively correlated to the ablation temperature (below 50 degrees C). Failure of MCV measurement occurred following exposures to 55 degrees celsius; for 50 s (or longer) or to 60 degrees C (or higher) for 10 s.

CONCLUSIONLow-temperature radiofrequency (below 50 degrees C) produces definite effects on the MCV of rat sciatic nerve, and the effects are not associated with the exposure time, the mechanism of which remains unclear. At a given temperature, the ablation for sufficiently long durations can result in complete block of the MCV. At higher temperatures, radiofrequency exposure cause obvious nerve conduction block.

Animals ; Electric Stimulation Therapy ; methods ; Female ; Male ; Motor Neurons ; physiology ; Neural Conduction ; Pain ; etiology ; Pain Management ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Sciatic Nerve ; injuries ; physiopathology ; Temperature ; Time Factors

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on cavernous nerve (CN) regeneration and functional status in a nerve-crush rat model. Twenty-four Sprague-Dawley male rats were randomly divided into three equal groups: eight had a sham operation, eight underwent bilateral nerve crushing with no further intervention and eight underwent bilateral nerve crushing with an immediate application of PRP on the site of injury. Erectile function was assessed by CN electrostimulation at 3 months and nerve regeneration was assessed by toluidine blue staining of CN and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining of penile tissue. Three months after surgery, in the group that underwent bilateral nerve crushing with no further intervention, the functional evaluation showed a lower mean maximal intracavernous pressure (ICP) and maximal ICP per mean arterial pressure (MAP) with CN stimulation than those in the sham group. In the group with an immediate application of PRP, the mean maximal ICP and maximal ICP/MAP were significantly higher than those in the injured control group. Histologically, the group with the application of PRP had more myelinated axons of CNs and more NADPH-diaphorase-positive nerve fibres than the injured control group but fewer than the sham group. These results show that the application of PRP to the site of CN-crush injury facilitates nerve regeneration and recovery of erectile function. Our research indicates that clinical application of PRP has potential repairing effect on CN and peripheral nerves.
Animals ; Disease Models, Animal ; Electric Stimulation ; Erectile Dysfunction ; pathology ; physiopathology ; therapy ; Male ; NADPH Dehydrogenase ; metabolism ; Nerve Regeneration ; physiology ; Penile Erection ; physiology ; Penis ; innervation ; Peripheral Nerve Injuries ; Peripheral Nerves ; metabolism ; pathology ; Platelet Transfusion ; Platelet-Rich Plasma ; Radiculopathy ; etiology ; pathology ; physiopathology ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the changes in sciatic nerve blood flow and the expression of collagen type I after electric injury of rabbit nerve with different voltages.

METHODSThirty-six healty rabbits were randomized into 3 groups before receiving injury with electricity in voltages, i.e. 50 v, 75 v, and 100 v groups. The changes in blood flow of sciatic nerve were observed with Laser Doppler Flowmeter immediately after injury and 1, 4, 8 weeks after injury. The changes in the expression of collagen type I was observed by immunohistochemical method, and the positive expression rate was calculated.

RESULTSThe sciatic nerve blood flow increased in all groups immediately after electric injury. In the 75 v and 100v groups, the nerve blood flow [(53 +/- 3 ), (48 +/- 5) PU] was obviously lower than that of normal value [(62 +/- 4) PU, P < 0.05]. There was little collagen type I deposition in 50 v group, while brown collagenous fibers in epineurium and perineurium were observed in 75 v and 100v groups 4 and 8 weeks after injury. The expression of collagen type I in all groups were obviously higher than that of normal value, and that in 75v and 100 v groups were higher than that in 50 v group at bachl time-point (P < 0.01).

CONCLUSIONThe restoration of sciatic nerve blood flow is postponed following by the injury with increase of the electrical voltage. The collagen deposition after electrical injury may be one of the reasons for nerve blood flow decrease.

Animals ; Collagen Type I ; biosynthesis ; Electric Injuries ; blood ; physiopathology ; Nerve Regeneration ; Rabbits ; Random Allocation ; Sciatic Nerve ; blood supply ; injuries

This paper reviews the current developing situation of neuroprostheses which are based on the functional electrical stimulation (FES) technique and are used to provide limb movements. It also discusses the major challenges of neuroprostheses, which will be faced in the future development and in the clinical applications for the rehabilitation of spinal cord injury and stroke.
Electric Stimulation Therapy ; methods ; trends ; Extremities ; physiology ; Humans ; Movement ; physiology ; Prostheses and Implants ; Prosthesis Design ; Spinal Cord Injuries ; physiopathology ; therapy ; Stroke ; physiopathology ; therapy

OBJECTIVES: To identify rat cavernous nerve and establish a rat model of erectile dysfunction caused by injury of cavernous nerve. METHODS: Ten rats were undergone dissections. 30 experimental rats were randomized into 2 groups, cavernous nerve were identified by electrical stimulation. One month after surgery, rat models were evaluated by electrical stimulation. RESULTS: The anatomic structure of cavernous nerve in rats are highly similar to human beings, the erection can be evoked by stimulating cavernous nerves, and after cavernous nerve injury it can not be evoked (P < 0.05). CONCLUSION Because of the highly similarity of cavernous nerve between rats and human beings, so as the suitable price, rat should be used as the ideal ED experimental animal. The model of ED caused by cavernous nerve injury is reliable.
Animals ; Disease Models, Animal ; Electric Stimulation ; Erectile Dysfunction/physiopathology* ; Ganglia, Autonomic/injuries* ; Male ; Penis/physiopathology* ; Rats ; Rats, Sprague-Dawley