Effect of methylprednisolone on motor function and spinal cord blood flow after spinal cord compression in rats

Effects of fluids vs. vasopressors on spinal cord microperfusion in hemorrhagic shock induced ischemia/reperfusion

OBJECTIVE

Spinal cord injury induced by ischemia/reperfusion is a devastating complication of aortic repair. Despite developments for prevention and treatment of spinal cord injury, incidence is still considerably high majorly impacting patient outcome. Microcirculation is paramount for tissue perfusion and oxygen supply and often dissociated from macrohemodynamic parameters used to guide resuscitation. Effects of fluids vs. vasopressors in the setting of hemodynamic resuscitation on spinal cord microperfusion are unknown. Aim of this study was to compare the effects of vasopressor and fluid resuscitation on spinal cord microperfusion in a translational acute pig model of hemorrhagic shock induced ischemia/reperfusion injury.

METHODS

We designed this study as prospective randomized explorative large animal study. We induced hemorrhagic shock in 20 pigs as a model of global ischemia/reperfusion injury. We randomized animals to receive either fluid or vasopressor resuscitation. We measured spinal cord microperfusion using fluorescent microspheres as well as laser-Doppler probes. We monitored and analyzed macrohemodynamic parameters and cerebrospinal fluid pressure.

RESULTS

Spinal cord microperfusion decreased following hemorrhagic shock induced ischemia/reperfusion injury. Both fluids and vasopressors sufficiently restored spinal cord microperfusion. There were no important changes between groups (percentage changes compared to baseline: fluids 14.0 (0.31-27.6) vs. vasopressors 24.3 (8.12-40.4), p = .340). However, cerebrospinal fluid pressure was higher in animals receiving fluid resuscitation (percentage changes compared to baseline: fluids 27.7 (12.6-42.8) vs. vasopressors -5.56 ((-19.8)-8.72), p = .003). Microcirculatory resuscitation was in line with improvements of macrohemodynamic parameters.

CONCLUSIONS

Both, fluids and vasopressors, equally restored spinal cord microperfusion in a porcine acute model of hemorrhagic shock induced ischemia/reperfusion injury. However, significant differences in cerebrospinal fluid pressure following resuscitation were present. Future studies should evaluate these effects in perfusion disruption induced ischemia/reperfusion conditions of microcirculatory deterioration.

Effect of carnosine, methylprednisolone and their combined application on irisin levels in the plasma and brain of rats with acute spinal cord injury

Spinal cord injury (SCI) might occur to anybody at any time and any age. In its treatment, methylprednisolone (MP) is a first choice worldwide, but there is still no significant breakthrough in truly beneficial treatment due to SCI's complex pathophysiology. We investigated the effect of carnosine, methylprednisolone (MP) and its combination on irisin levels in the plasma, brain and medulla spinalis tissues in SCI using a rat model. The rats were divided into 6 groups: I (Control, saline); II (sham animals with laminectomy without cross-clamping); III (SCI); IV (SCI treated with 150mg/kg carnosine); V (SCI treated with 30mg/kg methylprednisolone); and VI (SCI treated with a combination of carnosine and MP). The animals were given traumatic SCI after laminectomy, using 70-g closing force aneurysm clips (Yasargil FE 721). Irisin concentration was measured by ELISA. The distribution of irisin in brain and spinal cord tissues was examined by immunochemistry. Irisin was mainly expressed in the astrocytes and microglia of brain tissues, and multipolar neurones of the anterior horn of spinal cord tissue in rats of all groups, indicating that irisin is physiologically indispensable. MP and carnosine and the combination of the two, significantly increased irisin in plasma and were accompanied by a significant rise in irisin immunoreactivity of brain and spinal cord tissues of the injured rats compared with control and sham. This finding raises the possibility that methylprednisolone and carnosine regulate the brain and spinal cord tissues in SCI by inducing irisin expression, and may therefore offer a better neurological prognosis.

The rocky road to translation in spinal cord repair

Over the past 2 decades, the biological understanding of the mechanisms underlying structural and functional repair of the injured central nervous system has strongly increased. This has resulted in the development of multiple experimental treatment strategies with the collective aim of enhancing and surpassing the limited spontaneous recovery occurring in animal models and ultimately humans suffering from spinal cord or brain injuries. Several of these experimental treatments have revealed beneficial effects in animal models of spinal cord injury. With the exception of neurorehabilitative therapies, however, therapeutic interventions that enhance recovery are currently absent within the clinical realm of spinal cord injury. The present review surveys the prospects and challenges in experimental and clinical spinal cord repair. Major shortcomings in experimental research center on the difficulty of closely modeling human traumatic spinal cord injury in animals, the small number of investigations done on cervical spinal injury and tetraplegia, and the differences in lesion models, species, and functional outcome parameters used between laboratories. The main challenges in the clinical field of spinal cord repair are associated with the standardization and sensitivity of functional outcome measures, the definition of the inclusion/exclusion criteria for patient recruitment in trials, and the accuracy and reliability of an early diagnosis to predict subsequent neurological outcome. Research and clinical networks were recently created with the goal of optimizing animal studies and human trials. Promising clinical trials are currently in progress. The time has come to translate the biologic-mechanistic knowledge from basic science into efficacious treatments able to improve the conditions of humans suffering from spinal cord injury.

Animal studies in spinal cord injury: a systematic review of methylprednisolone

The objective of this study was to examine whether animal studies can reliably be used to determine the usefulness of methylprednisolone (MP) and other treatments for acute spinal cord injury (SCI) in humans. This was achieved by performing a systematic review of animal studies on the effects of MP administration on the functional outcome of acute SCI. Data were extracted from the published articles relating to: outcome; MP dosing regimen; species/strain; number of animals; methodological quality; type of injury induction; use of anaesthesia; functional scale used; and duration of follow-up. Subgroup analyses were performed, based on species or strain, injury method, MP dosing regimen, functional outcome measured, and methodological quality. Sixty-two studies were included, which involved a wide variety of animal species and strains. Overall, beneficial effects of MP administration were obtained in 34% of the studies, no effects in 58%, and mixed results in 8%. The results were inconsistent both among and within species, even when attempts were made to detect any patterns in the results through subgroup analyses. The results of this study demonstrate the barriers to the accurate prediction from animal studies of the effectiveness of MP in the treatment of acute SCI in humans. This underscores the need for the development and implementation of validated testing methods.

Comparison of inflammation in the brain and spinal cord following mechanical injury

Inflammation in the CNS predominantly involves microglia and macrophages, and is believed to be a significant cause of secondary injury following trauma. This study compares the microglial and macrophage response in the rat brain and spinal cord following discrete mechanical injury to better appreciate the degree to which these cells could contribute to secondary damage in these areas. We find that, 1 week after injury, the microglial and macrophage response is significantly greater in the spinal cord compared to the brain. This is the case for injuries to both gray and white matter. In addition, we observed a greater inflammatory response in white matter compared to gray matter within both the brain and spinal cord. Because activated microglia and macrophages appear to be effectors of secondary damage, a greater degree of inflammation in the spinal cord is likely to result in more extensive secondary damage. Tissue saving strategies utilizing anti-inflammatory treatments may therefore be more useful in traumatic spinal cord than brain injury.

The characteristics of neuronal injury in a static compression model of spinal cord injury in adult rats

Studies of spinal cord injury using contusion (impact) injury paradigms have shown that neuronal death is an acute event that is largely over within 24 h. However, much less is known about cell death following compression injury, despite compression being a key component of natural spinal injuries. We have therefore used neuronal nuclei (NeuN) immunostaining to examine the spatiotemporal pattern of neuronal loss after static compression injury in adult rats. 3D reconstruction was used to reveal the full effect of the injury. Neuronal loss at the injury epicentre, assessed by NeuN immunostaining, amounted to 44% at 1 day but increased to 73% at 3 days and 81% at 1 month. Neuronal loss was also seen 5 mm rostral and caudal to the epicentre, but was not significant until 3 days. NeuN loss was greatest in the ventral horns and in the intermediate grey matter, with the lateral dorsal horns relatively spared. Cystic cavities formed after injury, but were not evident until 4 weeks and were small in size. In contrast to the slow profile of neuronal loss, the compression injury also evoked a transient expression of activating transcription factor-3 (ATF3) and activated c-Jun in neurons. ATF3 expression peaked at 3 days and declined at 7 days. Our spatiotemporal analysis of compression injury shows that neuronal loss is much more protracted than in contusion injury, and highlights the potential for neuroprotective strategies. This study is also the first indication of ATF3 involvement in spinal cord injury.

Methylprednisolone causes minimal improvement after spinal cord injury in rats, contrasting with benefits of an anti-integrin treatment

Spinal cord injury (SCI) leads to complex secondary events that expand and exacerbate the injury. Methylprednisolone (MP) has been considered a standard of care for acute SCI. The purpose of this study was to test the effects of MP, in severe and more moderate severe clip-compression models of SCI, on the measures of neurological function and lesion sparing that we used previously to assess a highly effective anti-inflammatory therapy, a monoclonal antibody (mAb) to the CD11d integrin. Intravenous treatment with the anti-CD11d mAb blocks the infiltration of leukocytes into the lesion, limits secondary cord damage, and improves neurological outcomes. We also undertook a 2- week study of effects of these two therapies in combination. To permit direct comparison, the new findings with MP are presented together with reference to the previously published effects of the mAb. The severe SCI was at the 4(th) thoracic segment (T4), causing extensive motor dysfunction; the more moderate SCI was at T12 and caused less locomotor loss but the induction of mechanical allodynia. Neither MP alone nor the combination treatment improved Basso, Beattie, and Bresnahan 21-point open-field locomotor scores at 2-12 weeks after SCI. These scores were ~4 points in the control, MP, and combination treatment groups, respectively, at 2 weeks after severe SCI at T4. By 6 weeks after T4 SCI, scores in the control and MP groups were ~7. At 12 weeks after the more moderate T12 injury, scores were ~8 in both control and MP treatment groups. MP treatment had no consistent effect on mechanical allodynia during 12 weeks after SCI. Control and MP-treated rats responded to approximately five of 10 stimuli to their backs and three of 10 stimuli to their hind paws. MP treatment increased areas of neurofilament and myelin near the injury site at T4 and T12. Thus, MP treatment spared tissue, but had no corresponding effect on neurological function. In contrast, the combination treatment did not spare myelin significantly. These neurological outcomes after treatment with MP contrast with the consistent and significant improvements after treatment with the anti-CD11d mAb. Effects of MP on the lesion were significant, but myelin sparing was less than that caused by the anti-CD11d mAb. The presence of MP in the combination therapy appeared to reverse the positive effects of the mAb. The poor neurological outcome after MP treatment may relate to the long-lasting reduction in hematogenous monocyte/macrophages within the injury site that it causes and to the prolongation of a neutrophil presence. These findings demonstrate that the non-selective and enduring effects of immunosuppressive therapy with MP not only fail to improve neurological outcomes, but also can block the beneficial actions of selective therapies such as the anti-CD11d mAb. Combination treatments that cause intense immunosuppression should be viewed with caution.

Effect of postinjury intravenous or intrathecal methylprednisolone on spinal cord excitatory amino-acid release, nitric oxide generation, PGE2 synthesis, and myeloperoxidase content in a pig model of acute spinal cord injury

STUDY DESIGN

Prospective, randomized, in vivo acute spinal cord injury in pigs.

SETTING

Department of Anesthesiology, University of Washington, Seattle, WA, USA.

OBJECTIVES

To determine whether postinjury methylprednisolone could reduce the generation of known mediators of secondary neurological injury.

METHODS

Intrathecal microdialysis probes were used to sample cerebrospinal fluid (CSF) for measurement of PGE(2), glutamate, and citrulline (a byproduct of nitric oxide generation), before and after spinal cord injury in anesthetized pigs. The spinal cord was removed at the end of the study for measurement of myeloperoxidase and methylprednisolone concentrations. Animals were randomly allocated to receive intravenous methylprednisolone (30 mg/kg bolus then 3.4 mg/kg/h), intrathecal methylprednisolone (5 mg bolus then 5 mg/h), or saline, beginning 30 min after the spinal cord was injured by using a modification of the Allen weight drop technique.

RESULTS

Spinal cord injury significantly increased the amount of glutamate, PGE(2), myeloperoxidase, and citrulline, recovered from the CSF dialysates. However, neither intravenous nor intrathecal methylprednisolone administered after injury had any effect on the magnitude of the increase in any of the measured biochemicals. Intrathecal methylprednisolone administration produced a spinal cord methylprednisolone concentration that was eight times greater, and a plasma concentration that was 32 times less, than that achieved with intravenous administration.

CONCLUSIONS

Contrary to earlier animal studies in which methylprednisolone was administered either before or immediately after spinal cord injury, we found no effect of intravenous or intrathecal methylprednisolone on any of the parameters measured when administered 30 min postinjury.

Neuroprotection and acute spinal cord injury: a reappraisal

It has long been recognized that much of the post-traumatic degeneration of the spinal cord following injury is caused by a multi-factorial secondary injury process that occurs during the first minutes, hours, and days after spinal cord injury (SCI). A key biochemical event in that process is reactive oxygen-induced lipid peroxidation (LP). In 1990 the results of the Second National Acute Spinal Cord Injury Study (NASCIS II) were published, which showed that the administration of a high-dose regimen of the glucocorticoid steroid methylprednisolone (MP), which had been previously shown to inhibit post-traumatic LP in animal models of SCI, could improve neurological recovery in spinal-cord-injured humans. This resulted in the registration of high-dose MP for acute SCI in several countries, although not in the U.S. Nevertheless, this treatment quickly became the standard of care for acute SCI since the drug was already on the U.S. market for many other indications. Subsequently, it was demonstrated that the non-glucocorticoid 21-aminosteroid tirilazad could duplicate the antioxidant neuroprotective efficacy of MP in SCI models, and evidence of human efficacy was obtained in a third NASCIS trial (NASCIS III). In recent years, the use of high-dose MP in acute SCI has become controversial largely on the basis of the risk of serious adverse effects versus what is perceived to be on average a modest neurological benefit. The opiate receptor antagonist naloxone was also tested in NASCIS II based upon the demonstration of its beneficial effects in SCI models. Although it did not a significant overall effect, some evidence of efficacy was seen in incomplete (i.e., paretic) patients. The monosialoganglioside GM1 has also been examined in a recently completed clinical trial in which the patients first received high-dose MP treatment. However, GM1 failed to show any evidence of a significant enhancement in the extent of neurological recovery over the level afforded by MP therapy alone. The present paper reviews the past development of MP, naloxone, tirilazad, and GM1 for acute SCI, the ongoing MP-SCI controversy, identifies the regulatory complications involved in future SCI drug development, and suggests some promising neuroprotective approaches that could either replace or be used in combination with high-dose MP.

An Appraisal of Ongoing Experimental Procedures in Human Spinal Cord Injury

Clinicians and scientists in the field of spinal cord injury research and medicine are poised to begin translating promising new experimental findings into treatments for people. Advances in experimental regeneration research have led to several transplantation strategies that promote axonal regrowth and partial functional recovery in animal models of injury. In this review, we summarize current knowledge regarding various invasive experimental treatments that have been or are now being applied clinically. Various questions about the timeliness, safety, and benefits of the procedures are under discussion within the spinal cord injury (SCI) research community. We also describe guidelines for carrying out optimal clinical trials and efforts to establish specific international guidelines to translate preclinical treatment strategies into clinical trials in SCI. The clinical trial process and the role that clinical professionals have in advising individuals regarding participation in experimental procedures also is discussed.

Glutathione monoethyl ester improves functional recovery, enhances neuron survival, and stabilizes spinal cord blood flow after spinal cord injury in rats

Secondary damage after spinal cord (SC) injury remains without a clinically effective drug treatment. To explore the neuroprotective effects of cell-permeable reduced glutathione monoethyl ester (GSHE), rats subjected to SC contusion using the New York University impactor were randomly assigned to receive intraperitoneally GSHE (total dose of 12 mg/kg), methylprednisolone sodium succinate (total dose of 120 mg/kg), or saline solution as vehicle. Motor function, assessed using the Basso-Beattie-Bresnahan scale for 8 weeks, was significantly better in GSHE (11.2+/-0.6, mean+/-S.E.M., n=8, at 8 weeks) than methylprednisolone (9.3+/-0.6) and vehicle (9.4+/-0.7) groups. The number of neurons in the red nuclei labeled with FluoroRuby placed caudally to the injury site was significantly higher in GSHE (158+/-9.3 mean+/-S.E.M., n=4) compared with methylprednisolone (53+/-14.7) and vehicle (46+/-16.4) groups. Differences in the amount of spared SC tissue at the epicenter and neighboring areas were not significant among experimental groups. In a second series of experiments, using similar treatment groups (n=6), regional changes in microvascular SC blood flow were evaluated for 100 min by laser-Doppler flowmetry after clip compression injury. SC blood flow fell in vehicle-treated rats 20% below baseline and increased significantly with methylprednisolone approximately 12% above baseline; changes were not greater than 5% in rats given GSHE. In conclusion, GSHE given to rats early after moderate SC contusion/compression improves functional outcome and red nuclei neuron survival significantly better than methylprednisolone and vehicle, and stabilizes SC blood flow. These results support further investigation of reduced glutathione supplementation after acute SC injury for future clinical application.

Effects of methylprednisolone on the neural conduction of the motor evoked potentials in spinal cord injured rats

Methylprednisolone(MP), a glucocorticoid steroid, has an anti-inflammatory action and seems to inhibit the formation of oxygen free radicals produced during lipid peroxidation in a spinal cord injury(SCI). However, the effects of MP on the functional recovery after a SCI is controversial. The present study was conducted to determine the effects of MP on the recovery of neural conduction following a SCI. A SCI was produced using the NYU spinal cord impactor. A behavioral test was conducted to measure neurological disorders, and motor evoked potentials (MEPs) were recorded. According to the behavioral test, using BBB locomotor scaling, MP-treated animals showed improved functional recoveries when compared to saline-treated animals. MEP latencies in the MP-treated group were shortened when compared to those in the control group. Peak amplitudes of MEPs were larger in the MP-treated group than those in the control group. The thresholds of MEPs tended to be lower in the MP-treated group than those in the control group. These results suggest that MP may improve functional recovery after a SCI.

Spinal blood flow in 24-hour megadose glucocorticoid treatment in awake pigs

OBJECT

Because of the controversy regarding the benefits of 24-hour administration of methylprednisolone in patients with spinal cord injury (SCI), it is important to investigate its mechanism of action and side effects. This study was conducted to determine if high-dose methylprednisolone modulates neural and vertebral blood flow in an awake large-sized animal model without SCI.

METHODS

From a group of 18 immature female domestic pigs born to nine different litters, nine animals were randomly allocated to receive methylprednisolone treatment, whereas their nine female siblings served as controls. Drug or placebo was applied in a blinded fashion by a third person not involved in the study. The following treatment for SCI, as suggested by the North American Spinal Cord Injury Study, was administered to the awake pig: methylprednisolone (30 mg/kg of body weight) was infused into the jugular vein during a 15-minute period, followed by a 45-minute pause, and the infusion was maintained over a 23-hour period at a dose of 5.4 mg/kg body weight/hour. By means of the radioactive tracer microsphere technique, spinal cord blood flow (SCBF) was measured in the awake standing pig in the cerebrum, and in spinal gray and white matter, nerve roots, endplates, cancellous bone, cortical shell, and T12-L2 discs. Blood flow was measured before, 1 hour after initiation of infusion, and 24 hours postinfusion. Examination of blood flow in the neural and vertebral tissue samples, as well as of central hemodynamics, revealed no significant difference between the experimental and control groups, and this parity was maintained throughout the experimental phases.

CONCLUSIONS

In the awake pig model, 24-hour methylprednisolone treatment does not modulate cerebral or SCBF, nor does it increase the risk for vertebral osteonecrosis by producing vertebral ischemia.

Long-term effects of methylprednisolone following transection of adult rat spinal cord

Clinically, high-dose treatment with the glucocorticosteroid, methylprednisolone (MP), within 8 h after spinal cord injury, has been shown to improve neurological recovery. The current standard of care is to administer MP as a bolus of 30 mg/kg followed by a 23-h infusion of 5.4 mg/kg/h to spinal cord injured patients. To better understand the role of MP in neuroprotection, we have studied how MP administration affects macrophage accumulation, tissue loss, and axonal dieback at 1, 2, 4 and 8 weeks after a complete transection of the eighth thoracic spinal cord in the adult rat. A 30 mg/kg dose of MP was administered intravenously at 5 min, and 2 and 4 h after injury. The number of ED1 (antibody against microglia/macrophages) -positive cells was quantified in a 500-micrometer-wide strip of tissue directly adjacent and parallel to the transection. At all time points, MP treatment led to a significant decrease in the number of ED1-positive cells in both rostral and caudal stumps. Over the 2-month post-transection period, the average MP-induced reduction in the number of ED1-positive cells was 82% in the rostral cord stump and 66% in the caudal stump. Using a computerized image analysis system, it was observed that MP treatment resulted in a significant reduction in tissue loss in both cord stumps at 2, 4 and 8 week post-injury. Over the 2-month post-lesion period, the average MP-induced reduction in tissue loss in the caudal cord stump was higher than that in the rostral stump; 48 versus 37%, respectively. Immunostaining for neurofilaments and growth-associated protein-43 (GAP-43) revealed the presence of numerous axons near and in the lesion site. Anterograde neuronal tracing with biotinylated dextran amine showed that, in MP-treated animals, dieback of vestibulospinal fibres, but not of corticospinal fibres, was significantly diminished at all time points studied. In addition, with MP administration, 1 and 2 weeks after injury, an increase in the number of vestibulospinal fibres was found at 1 and 2 mm from the transection, suggesting transient regenerative sprouting of these fibres. The results demonstrate that treatment with MP shortly after spinal cord transection in the adult rat led to a long-term reduction of ED1-positive cells and spinal tissue loss, reduced dieback of vestibulospinal fibres, and a transient sprouting of vestibulospinal fibres near the lesion at 1 and 2 weeks post-lesion. The possible relationships between the inflammatory changes, spinal tissue sparing, and axonal survival and sprouting are complex and need to be further explored.

Effects of alpha-phenyl-N-tert-butyl nitrone (PBN) on compression injury of rat spinal cord

alpha-Phenyl-N-tert-butyl Nitrone (PBN) is a free radical scavenger which recently has proved to be neuroprotective in experimental studies on focal cerebral ischemia and infarction. We therefore studied the effect of this drug in a model of moderate compression injury to rat spinal cord at the midthoracic level. The compound was given intraperitoneally 0.5 h before (100 mg/kg b.w) and at 1.5 h (50 mg/kg b.w) and 3.5 h (50 mg/kg b.w) after compression. Treated animals and controls (vehicle alone) were allowed to survive for 1 or 9 days following trauma. The functional outcome was tested by the inclined plane method and the motor performance score. By using MAP2 immunostaining the number of nerve cell bodies in the ventral horn and the ratio of MAP2 immunostained area to area of whole section of the cord were assessed to detect loss of neurons and loss of dendrites in the compressed segment. beta APP and PGP9.5 immunostaining was used to demonstrate axonal lesions. Treated and control rats showed at day 1 when tested with the inclined plane method a marked reduction of the capacity angle. This abnormality recovered gradually over the following days and was normalized at day 9. The motor performance score showed a marked reduction at day 1 which almost normalized at day 9. There was no difference regarding the functional outcome between rats given PBN and controls in none one of these functional tests. The spinal cord of normal rats presented immunoreactivity to MAP2 in nerve cell bodies and dendrites but not in axons and other structures. Following compression there was at day 1 and 9 a marked loss of MAP2 immunoreactivity in dendrites and nerve cell bodies. We could not detect any difference between the PBN and the control rats regarding the degree of cell loss or degree of reduction of dendrite staining. No difference between the two groups was seen with the axonal immunostainings (beta APP and PGP9.5). In conclusion, our study did not reveal any neuroprotective effect of PBN on the functional outcome and morphology (immunostaining to MAP2, beta APP and PGP9.5) in this model of moderate compression trauma to rat spinal cord.

Effect of 21-aminosteroid on extracellular energy-related metabolites and amino acids after compression injury of rat spinal cord

We evaluated in a rat model of severe spinal cord compression the effect of the 21-aminosteroid tirilazad on extracellular levels of energy metabolites and amino acids, until 3 h after injury. The compound was given i.v. 30 min before injury (3 mg/kg) and hourly thereafter (1.5 mg/kg). The findings were compared with previously reported effects of methylprednisolone. Both treated and untreated rats with spinal cord compression showed, at 10 min after injury, a five- to sixfold elevation of extracellular lactate above the preinjury level. There was no significant difference for lactate, pyruvate or lactate/pyruvate ratio between the treated and untreated injured groups at any time point after trauma. Glutamate was significantly elevated both in treated and untreated injured rats for 20 min after trauma. The mean glutamate level was lower in animals treated with 21-aminosteroid. However, there was no statistically significant difference between the treated and untreated rats at any time after trauma. There was no statistically significant difference between the groups for aspartate, serine, glutamine, histidine, glycine, threonine, taurine, alanine and tyrosine. In conclusion our findings indicate that, in the injured spinal cord, methylprednisolone and the 21-aminosteroid have differences and similarities, regarding their effects on energy and amino acid metabolism. The lowering of the lactate and arginine levels early after trauma seen with methylprednisolone pretreatment was absent after 21-aminosteroid pretreatment. However, the mean extracellular level of glutamate was lower with both methylprednisolone and 21-aminosteroid after injury, although the difference was not statistically significant between treated and untreated rats.

Beneficial effects of the melanocortin alpha-melanocyte-stimulating hormone on clinical and neurophysiological recovery after experimental spinal cord injury

OBJECTIVE

Melanocortins, peptides related to melanocyte-stimulating hormone (MSH) and corticotropin (ACTH), exhibit neurotrophic and neuroprotective activity in several established models of peripheral and central nervous system damage. The beneficial effects of melanocortins on functional recovery after experimental brain damage and central demyelinating diseases have prompted us to investigate alpha MSH treatment in a weight drop model of traumatic spinal cord injury in rats.

METHODS

In two independent randomized blinded experiments, treatment with either alpha MSH (75 micrograms/kg of body weight administered subcutaneously every 48 h for 3 weeks after trauma) or single high-dose (30 mg/kg, 30 min after injury) methylprednisolone was compared with saline treatment in rats subjected to a moderately severe 20-gcm weight drop injury. Spinal cord function was monitored using behavioral, electrophysiological, and histological parameters.

RESULTS

In both experiments, alpha MSH significantly improved recovery, as illustrated by Tarlov scores, thoracolumbar height, and amplitude of rubrospinal motor evoked potentials. The magnitude of the alpha MSH effect on motor performance was comparable with the one observed after treatment with methylprednisolone.

CONCLUSION

The reproducible neurological and electrophysiological improvement in spinal cord function of animals treated with alpha MSH suggests a new lead in the treatment of traumatic spinal cord injury.

Effects of methylprednisolone on lesioned and uninjured mammalian spinal neurons: viability, ultrastructure, and network electrophysiology

An in vitro investigation was undertaken to provide information regarding the effectiveness of methylprednisolone sodium succinate (MPSS) as a treatment for the primary mechanical injury of spinal cord (SC) trauma. Exposure of uninjured mouse SC cells to MPSS for 24 h caused neuronal stress when the concentration exceeded 150 micrograms/mL; neuronal death occurred at concentrations above 600 micrograms/mL. The concentration range for MPSS protection of SC neurons subjected to a defined physical injury (laser microbeam transection of a primary dendrite 100 microns from the perikaryon) was very narrow: survival in the 30 micrograms/mL group differed significantly from the untreated control group (68.5% +/- 14.1 vs. 47.1% +/- 14.1), treatment with 20 or 60 micrograms/mL MPSS did not increase survival, and treatment with 100 micrograms/mL MPSS accelerated ultrastructural deterioration and increased the likelihood of death. Enhanced survival of lesioned neurons was observed when 30 micrograms/mL MPSS was applied within 15 min of dendrotomy but not when MPSS was administered 2 h after lesioning. Multimicroelectrode plate (MMEP) studies of SC network electrical activity indicated that MPSS associated readily with neuronal membranes. This finding was consistent with the hypothesis that MPSS may protect lesioned neurons by stabilizing damaged membranes, enhancing lesion resealing, and limiting the spread of ion-mediated damage. However, comparisons of neurite die-back 24 h after dendrotomy found no significant difference between MPSS-treated and control neurons. Application of 30 or 100 micrograms/mL MPSS increased the spontaneous burst activity of SC networks grown on MMEPs, however, there was no evidence that the increased excitability at these concentrations was the result of specific actions of MPSS on GABA or NMDA synapses.

The neuroprotective effect of high-dose methylprednisolone in rat spinal cord hemisection

Multiple studies support a neuroprotective effect for high-dose methylprednisolone (MP) in acute blunt spinal cord injury. We know of no study that addresses the role of MP in prophylaxis for surgical trauma to the spinal cord or for the treatment of non-missile penetrating injuries to the spinal cord. We examined the neuroprotective effect of MP as measured by the retrograde transport of the fluorescent tracer Fluoro-Gold in 20 rats undergoing C-2 hemisection. Mean cell counts of retrogradely labeled rubrospinal neurons were determined 1 week post-injury. The group receiving MP had a significantly higher (P < 0.0001) number of labeled cells (x = 594) compared to controls (x = 387). The highly significant increase in mean cell counts in rats receiving steroids suggests less secondary axonal injury in the MP group. These findings are the first report of a neuroprotective effect of MP in rat spinal cord hemisection. We suggest that MP may be beneficial as prophylaxis during planned or incidental surgical trauma to the spinal cord and after non-missile penetrating injuries to the spinal cord.

Methylprednisolone inhibits early inflammatory processes but not ischemic cell death after experimental spinal cord lesion in the rat

Experimental studies and clinical observations show that spinal cord lesions are greatly enlarged by a process called secondary cell death. A detailed understanding of the molecular and cellular processes underlying these events is still lacking. In clinical studies using methylprednisolone in spinal cord injured patients a mega-dose of methylprednisolone applied during the first few hours after injury was found to improve the neurological outcome. In the present study the possible neuroprotective mechanism of methylprednisolone was assessed by histologically studying its effect on the extent of secondary cell death and on early inflammatory reactions following partial transection of the spinal cord in the rat. Our results show that a single high dose of 30 or 60 mg/kg methylprednisolone affects neither the time course nor the extent of secondary cell death. In contrast, methylprednisolone markedly suppressed the invasion of the injured spinal cord tissue by polymorphonuclear granulocytes and macrophages. The role of these inflammatory cells in traumatic CNS lesions is very unclear at present. It is possible that they lead to further damage of the injured spinal cord tissue and that the beneficial effect of methylprednisolone is at least partially due to its anti-inflammatory effect, thereby inhibiting bystander damage of invading inflammatory cells.

Animal model of spinal cord infarction induced by cholesterol embolization

Though several animal models of ischemic brain infarction have been developed, no animal model of purely ischemic spinal cord infarction exists. In humans, such paralysis often occurs as a complication of aortic surgery. While working on an animal model of cholesterol embolic renal disease, the authors produced an animal model of ischemic spinal paralysis by direct intraaortic injection of cholesterol suspension. With histologic examination of spinal cords of the paralyzed rats, prominent cholesterol crystals were found obliterating the lumen of the anterior and/or posterior spinal arteries. Spinal cord infarction was seen most prominently in the lateral columns and anterior horns, though other areas also were affected. Permanent paraplegia developed in most rats, but transient paralysis developed in a few, followed by partial or full recovery. This model of spinal infarction in nonanesthetized rats can be used to study the pathophysiology and therapy of spinal infarction.

The effects of methylprednisolone and the ganglioside GM1 on acute spinal cord injury in rats

Recent clinical trials have reported that methylprednisolone sodium succinate (MP) or the monosialic ganglioside GM1 improves neurological recovery in human spinal cord injury. Because GM1 may have additive or synergistic effects when used with MP, the authors compared MP, GM1, and MP+GM1 treatments in a graded rat spinal cord contusion model. Spinal cord injury was caused by dropping a rod weighing 10 gm from a height of 1.25, 2.5, or 5.0 cm onto the rat spinal cord at T-10, which had been exposed via laminectomy. The lesion volumes were quantified from spinal cord Na and K shifts at 24 hours after injury and the results were verified histologically in separate experiments. A single dose of MP (30 mg/kg), given 5 minutes after injury, reduced 24-hour spinal cord lesion volumes by 56% (p = 0.0052), 28% (p = 0.0065), and 13% (p > 0.05) in the three injury-severity groups, respectively, compared to similarly injured control groups treated with vehicle only. Methylprednisolone also prevented injury-induced hyponatremia and increased body weight loss in the spine-injured rats. When used alone, GM1 (10 to 30 mg/kg) had little or no effect on any measured variable compared to vehicle controls; when given concomitantly with MP, GM1 blocked the neuroprotective effects of MP. At a dose of 3 mg/kg, GM1 partially prevented MP-induced reductions in lesion volumes, while 10 to 30 mg/kg of GM1 completely blocked these effects of MP. The effects of MP on injury-induced hyponatremia and body weight loss were also blocked by GM1. Thus, GM1 antagonized both central and peripheral effects of MP in spine-injured rats. Until this interaction is clarified, the authors recommend that MP and GM1 not be used concomitantly to treat acute human spinal cord injury. Because GM1 modulates protein kinase activity, protein kinases inhibit lipocortins, and lipocortins mediate anti-inflammatory effects of glucocorticoids, it is proposed that the neuroprotective effects of MP are partially due to anti-inflammatory effects and that GM1 antagonizes the effects of MP by inhibiting lipocortin. Possible beneficial effects of GM1 reported in central nervous system injury may be related to the effects on neural recovery rather than acute injury processes.

Effect of nimodipine or methylprednisolone on recovery from acute experimental spinal cord injury in rats

The purpose of the present study was to examine the behavioral, electrophysiologic, and anatomic responses to nimodipine or methylprednisolone treatment of acute experimental spinal cord injury. Four groups of rats were injured at T1 by compressing the cord with a 52-g clip for 1 minute. The treatments were begun 15 minutes after injury, and the animals were observed thereafter for 8 weeks. Nimodipine 0.02 mg/kg/h intravenously (iv) for 8 hours with adjuvant albumen volume expansion, followed by 20 mg/kg nimodipine enterally three times per day for 7 days, produced a moderately better composite score comprising four endpoint parameters than the other treatments which consisted of nimodipine iv for 8 hours only, methylprednisolone 30 mg/kg iv bolus followed by 5.4 mg/kg/h iv for 8 hours, or control.

Limiting ischemic spinal cord injury using a free radical scavenger 21-aminosteroid and/or cerebrospinal fluid drainage

Traumatic spinal cord injury occurs in two phases: biomechanical injury, followed by ischemia and reperfusion injury. Biomechanical injury to the spinal cord, preceded or followed by various pharmaceutical manipulations or interventions, has been studied, but the ischemia/reperfusion aspect of spinal cord injury isolated from the biomechanical injury has not been previously evaluated. In the current study, ischemia to the lumbar spinal cord was induced in albino rabbits via infrarenal aortic occlusion, and two interventions were analyzed: the use of U74006F (Tirilazad mesylate), a 21-aminosteroid, and cerebrospinal fluid (CSF) drainage. These treatment modalities were tested alone or in combination. In Phase 1 of this study, the rabbits received 1.0 mg/kg of Tirilazad or an equal volume of vehicle (controls) prior to the actual occlusion, three doses of Tirilazad (1 mg/kg each) during the occlusion, then several doses after the occlusion. Of the Tirilazad-treated animals, 30% became paraplegic while 70% of the control animals became paraplegic. Phase 2 involved the same doses of Tirilazad as in Phase 1 and, in addition, CSF pressure monitoring and drainage were performed. The paraplegia rate was 79% in the control animals, 36% in the group receiving Tirilazad alone, 25% in the group with CSF drainage alone, and 20% in the Tirilazad plus CSF drainage group. This rate also correlated with changes noted in CSF pressure; both Tirilazad administration alone and CSF drainage alone induced a decrease in CSF pressure and the two combined produced a further decrease. There was marked improvement in the perfusion pressure when using Tirilazad alone, CSF drainage alone, and Tirilazad therapy in combination with CSF drainage, with the last group producing the largest increase. This change in CSF pressure and perfusion pressure correlated with improved functional neurological outcome. Pathological examination revealed that Tirilazad therapy reduced the extensive and diffuse neuronal, glial, and endothelial damage to (in its most severe form) a more patchy focal region of damage in the gray matter. Cerebrospinal fluid drainage resulted in pyknosis of some motor neurons, and some eosinophilia. The combination of CSF drainage and Tirilazad administration resulted in the least abnormality, with either normal or near-normal spinal cords. It is concluded that Tirilazad administration decreased CSF pressure during spinal cord ischemia and reperfusion and, like CSF drainage, increased and improved the perfusion pressure to the spinal cord, decreased spinal cord damage, and improved functional outcome.(ABSTRACT TRUNCATED AT 400 WORDS)

Spinal cord blood flow and evoked potential responses after treatment with nimodipine or methylprednisolone in spinal cord-injured rats

This study examined the effect of nimodipine or methylprednisolone on spinal cord blood flow (SCBF) and electrophysiological function after spinal cord injury in rats. Three groups of male rats (n = 10 per group) were injured by compression of the cord at T1 for 1 minute with a 52-g clip. The hydrogen clearance technique was used to measure SCBF at the T1 segment. Motor and somatosensory evoked potentials were recorded. SCBF and evoked potentials were measured before injury and again at approximately 1 and 2.5 hours after injury. The methylprednisolone group received a bolus of methylprednisolone (30 mg/kg) at 5 minutes after injury and then at 15 minutes after injury, the group received an infusion of methylprednisolone at 5.4 mg/kg per hour. The nimodipine group received placebo at 5 minutes and then received an infusion of nimodipine at 0.02 mg/kg per hour at 15 minutes. The placebo group received placebo at both times. Physiological parameters were closely monitored and maintained within the normal range. Albumin was administered after injury to maintain mean arterial blood pressure at or above 80 mm Hg. The infusions were continued for approximately 3 hours after spinal cord injury. SCBF was not significantly different between the experimental groups at either 1 or 2.5 hours postinjury (P = 0.16 and 0.71, respectively), and evoked potential responses did not return in any rat at any time after injury. Thus, this experiment failed to demonstrate an improvement in SCBF or electrophysiological function with either drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroprotective actions of glucocorticoid and nonglucocorticoid steroids in acute neuronal injury

1. The glucocorticoid steroid methylprednisolone (MP) has been shown to enhance chronic recovery after human spinal cord injury when administered in a 24-hr high-dose regimen beginning within 8 hr. The doses of MP that affect this improved recovery have been demonstrated to inhibit posttraumatic spinal cord lipid peroxidation (LP), which has been postulated to be a key event in the secondary injury-induced degenerative cascade. 2. The molecular mechanism of action of the steroid appears to involve intercalation into the cell membrane and blockade of the propagation of peroxidative reactions. At a physiological level, the inhibition of injury-induced LP has been found to result in an attenuation of progressive posttraumatic ischemia and energy failure together with an augmented reversal of intracellular calcium accumulation. However, MP also acts directly to retard secondary neuronal degeneration as observed in studies showing the steroid's ability to slow the anterograde degeneration of experimentally injured cat soleus motor nerves. 3. The duplication of this effect by the nonsteroidal lipid antioxidant alpha-tocopherol supports the notion that is indeed a manifestation of the inhibition of posttraumatic LP. Moreover, the efficacy of MP in limiting lipid peroxidation and secondary spinal cord or motor nerve degeneration has also been duplicated by a nonglucocorticoid 21-aminosteroid tirilazad mesylate (U-74006F), which suggests the independence of the antioxidant and glucocorticoid effects of MP.

Lipid antioxidants in acute central nervous system injury

Oxygen radical-mediated lipid peroxidation increasingly has been suggested to be an important factor in post-traumatic neuronal degeneration. Thus, numerous studies have evaluated the neuroprotective efficacy of pharmacologic agents with lipid antioxidant activity in models of spinal cord and brain injury. The glucocorticoid steroid methylprednisolone has been shown to possess significant antioxidant efficacy, and when administered to animals or human beings in antioxidant doses, it improves chronic neurologic recovery after spinal cord injury. This activity of methylprednisolone is independent of the steroid's glucocorticoid receptor-mediated actions and has been surpassed by the novel antioxidant 21-aminosteroids that have been developed that are devoid of glucocorticoid activity but have greater antioxidant efficacy than methylprednisolone. One of these, tirilazad mesylate (U-74006F), has been shown to be quite effective in animal models of brain and spinal cord injury and is the subject of phase III clinical trials. The consistent benefit afforded by antioxidant compounds further supports the concept that lipid peroxidation is an important therapeutic target for acute pharmacologic neuroprotection.

Pathophysiology of spinal cord trauma

This article reviews the pathophysiology of spinal cord injury. The focus is on the role of post-traumatic membrane lipid changes, including lipid hydrolysis with enzymatic lipid peroxidation (ie, eicosanoid production) and nonenzymatic, free radical-induced lipid peroxidation in the secondary autodestruction of injured spinal cord tissue. A speculative etiopathogenesis of secondary injury is presented in an attempt to explain the importance and order of the pathophysiologic events that result in tissue death and the apparent effectiveness of diverse pharmacologic agents in the treatment of experimental spinal cord injury.

Methylprednisolone reduces excitatory amino acid release following experimental spinal cord injury

Administration of methylprednisolone within several hours after injury to the spinal cord has been shown to reduce subsequent impairment in humans and experimental animals. Secondary damage following initial trauma is probably caused in part by the toxicity of released excitatory amino acids. We demonstrate here that methylprednisolone reduces the release of excitatory amino acids following experimental spinal cord injury in rats.

The neuroprotective pharmacology of methylprednisolone

A 24-hour intensive intravenous dosing regimen with the glucocorticoid steroid methylprednisolone has recently been shown to be effective in enhancing neurological recovery in spinal cord-injured patients when initiated within 8 hours after injury. The state of knowledge concerning the neuroprotective pharmacology of methylprednisolone, including mechanism(s) of action, dosing requirements, and time-action considerations is reviewed, as are the results of studies with high doses in experimental and clinical head injury, subarachnoid hemorrhage, and cerebral ischemia. A primary neuroprotective mechanism of action in each of these cases is hypothesized to involve the ability of high doses of methylprednisolone to inhibit oxygen free radical-induced lipid peroxidation, although additional mechanisms may contribute. Unresolved issues are also addressed, including the therapeutic window, optimum duration of treatment, and rational combination with other neuroprotective agents. A newer methylprednisolone pro-drug with improved solution stability is discussed, together with a brief consideration of novel nonglucocorticoid steroids that surpass methylprednisolone's lipid antioxidant effects without unwanted glucocorticoid properties.

MK 801, an OBS N-methyl-D-aspartate channel blocker, does not improve the functional recovery nor spinal cord blood flow after spinal cord compression in rats

Damage to the central nervous system is followed by local release of excitatory amino acids, e.g. glutamate. These have been claimed to increase the metabolic need of already hypoxic neurons, and thereby to promote cell death. To investigate whether N-methyl-D-aspartate (NMDA) receptor-mediated mechanisms are involved in the damage consequent to spinal cord injury, 20 rats were exposed to 5-min compression of the thoracic spinal cord produced with a load of 35 g on a 2.2 x 5 mm sized plate. One group of animals was given a noncompetitive NMDA channel blocker, MK-801, in a dose of 10 mg/kg b.w and one group saline alone. The neurologic function was evaluated on the inclined plane for 4 days when spinal cord blood flow (SCBF) was measured with the 14C-iodoantipyrine autoradiographic technique. One day after trauma the animals in both groups were paraparetic and exhibited a significantly decreased capacity angle at the inclined plane test (about 35 degrees compared with about 63 degrees before compression). Thereafter, the motor function improved slightly, but to a similar extent in the two groups. On Day 4, gray and white matter SCBF was similar in the two groups. The results indicate that MK 801 in the dose used does not prevent the development of neurologic dysfunction or the reduction in SCBF after spinal cord compression.

Naloxone and experimental spinal cord injury: effect of varying dose and intensity of injury

We have reported previously that high-dose (10 mg/kg) and megadose naloxone (as high as 150 mg/kg) failed to promote recovery of motor function after spinal cord injury in rat. In view of these negative results, in comparison to some reports of benefit of naloxone in the literature, the present study was undertaken to assess lower doses, using a modified 3 x 4 factorial design, to evaluate a range of lower doses in relation to various intensities of cord injury. Sprague-Dawley rats were assigned randomly to 10 groups (n = 10) relating to two factors: intensity of injury and dosage of naloxone. A dynamic-load injury was induced with a 10-g weight dropped from a height of 2.5 cm, 5.0 cm, or 17.5 cm. Animals were treated with naloxone 1 mg/kg, 4 mg/kg, 10 mg/kg, or saline (control). Tests of motor recovery were carried out weekly for 4 weeks postinjury. Histopathological morphometric analysis of the spinal cords was carried out for measurement of residual gray and white matter at the epicenter of the cord injury. In general, the behavioral data showed no improvement in recovery of function, with the possible exception of naloxone at a dosage of 4 mg/kg (not statistically significant at 4 weeks). Independent of naloxone treatment, there was a significant difference among the three intensities of injury. Pathologically, a difference could not be demonstrated in relation to dosage of naloxone, but as in the case of the behavioral data, a graded response occurred as a function of intensity of injury.

Blocking weight-induced spinal cord injury in rats: therapeutic effect of the 21-aminosteroid U74006F

The effect of the 21-aminosteroid U74006F on neurologic recovery after a spinal cord compression trauma was investigated in rats. The compression was induced by a blocking weight technique, in which a 35 g (moderate injury) or a 50 g (severe injury) weight was applied for 5 minutes to an 11 mm2 plate over the midthoracic spinal cord. One hour after trauma, the severely injured animals were treated either with U74006F, 3 mg/kg, methylprednisolone, 30 mg/kg, or vehicle, whereas the moderately injured animals received U74006F, 3 mg/kg or vehicle. Neurologic hind limb function was evaluated by the inclined plane technique. On day 1 after trauma, subtotal paraparesis occurred in the 35 g group treated with vehicle (31 +/- 1 degrees, mean +/- SEM) on the inclined plane vs 64 +/- 1 degrees before trauma) and complete paraplegia in the 50 g group (22 +/- 1 degrees). Treatment with U74006F resulted in less hind limb weakness in the 35 g group (42 +/- 2 degrees) but had no beneficial effect in the 50 g group (25 +/- 2 degrees). Neurologic function gradually improved in the 35 g groups over the 9-day observation period. However, those animals treated with U74006F were significantly better over the entire period. In the 50 g group, no recovery from paraplegia was noted over the 4 day observation period in any of the three groups. These results suggest that after weight-induced spinal cord trauma, U74006F is associated with improved neurologic function in moderately injured, but not severely injured animals.