Vasoactive intestinal polypeptide neurons in fetal cortical homografts to adult rat spinal cord

Transplants of central nervous system to adult spinal cords are considered as potential aids in regeneration of the spinal cord and/or recovery of function after injury. The organization and development of the implant are important issues in seeking the potential for a transplant and host to become functionally integrated. This study uses embryonic cerebral cortex transplanted into the spinal cord of adult rats (T6) and examined the development and organization of the transplant with an antibody to vasoactive intestinal polypeptide (VIP). The cell bodies of VIP neurons are in the implants at 30 days postimplantation, but few of the somata have processes. By 45 days postimplantation, VIP neurons in the implant have dendrites and axons and are clearly recognizable as cortical bipolar cells which are not normally present in the thoracic spinal cord. These data show that neurons in embryonic cerebral cortical implants into the spinal cord elaborate the appropriate biochemical and morphological constituents in spite of the ectopic location. However, the cell processes develop at a slower than normal pace. Morphological interaction between the host spinal cord and the implant can be demonstrated possibly as early as 45 days postimplantation and clearly at 6 months following the implant. Thus, further examination of cerebral cortical implants as a potential aid in allevation of paraplegia subsequent to spinal cord injury is warranted.     

Ependyma formation in adult rat spinal cord after transplantation of fetal cerebral cortex homografts

The ependymal cells in rat host spinal cord were studied after transplantation of fetal cerebral cortex homografts. Adult Sprague-Dawley male rats had pieces of E14 fetal rat cortex pressure-injected into the spinal cord at T6. The tissue was prepared for light and electron microscopy and studied for over 2 months postimplantation. At 7 and 14 days postimplantation (DPI), there were dividing ventricular-ependymal cells lining cysts in the host spinal cord. After 21 days, cell division was no longer observed in these cells, and only mature ependymal cells lined these cysts. Mature ependymal cells were either: columnar, pseudocolumnar, cuboidal, squamous, or pseudomorphic; had cilia and villi on only one surface of the cell and shared tight junctions when contiguous. These data show that ependymal cells were mature cellular components of adult spinal cord after transplantation of fetal CNS grafts. In addition, ventricular-ependymal cells continued to divide within the parenchyma of the graft, indicating continued growth of transplanted fetal cerebral cortex in host spinal cord.     

Migration of cultured fetal spinal cord astrocytes into adult host cervical cord and medulla following transplantation into thoracic spinal cord

Cell suspensions from 14-day-gestation rat spinal cord, which had previously been soaked for 1 hr in a 2 micrograms/ml solution of Phaseolus vulgaris leucoagglutinin (PHAL), were cultured on collagen gels containing laminin for 2 weeks. Pieces of the gel and attached cells were then transplanted into the dorsal column of adult host thoracic spinal cord. At 1, 2, and 3 months postimplantation (MPI), animals were sacrificed, and the spinal cords were removed, embedded in paraffin, and sectioned at 8 micron for immunohistochemistry at the light microscopic level. Sections were double labeled for PHAL and utilized as a marker for transplant-derived cells and glial fibrillary acidic protein (GFAP), a specific marker for astrocytes. Transplant-derived astrocytes (PHAL-GFAP positive cells) migrated from the transplantation site in both rostral and caudal directions and were observed within the host dorsal column ipsilateral to the transplantation site. At 2 months, lateral migration into the contralateral dorsal column and ipsilateral dorsal horn was observed. At 3 MPI transplant-derived astrocytes were observed in host medulla (nucleus gracilis). Transplant-derived astrocytes were also observed on the glial limitans as far as nucleus gracilis. A migration rate of 0.72 mm/day was calculated, assuming a 14-day delay in the initiation of migration. The ramifications of such extensive migration are discussed with regard to return of function and amelioration of lesion-induced deficits.     

Ultrastructure of fetal spinal cord and cortex implants into adult rat spinal cord

The ultrastructure of cortex and spinal cord from 11-, 12-, and 15-day-old fetuses implanted into the spinal cord of adult rats was studied over 3 months. Under deep Chloropent anesthesia, a 0.5 × 1.0-mm square of fetal cortex or a 1.0-mm segment of fetal spinal cord was implanted subpially between the left dorsal column and the dorsal horn of 70 adult rats. Implants grew toward gray matter, usually interfacing with the host at the isthmus between the horns of the spinal cord. However, implants were observed that occupied the entire left dorsal and ventral horns of the left half of the host spinal cord. Implants had concentric zones: A central zone with basal lamina lined joined channels and subjacent neuroglia; a zone of differentiating implant nervous system; a zone with basal lamina lined implant with overlying pial cells on the dorsal and lateral surfaces of the implant; a zone that interfaced with the host with overlapping neuropil on the lateral and ventral surfaces of the implant. Neuron types were typical for cortical or spinal implants. Implants survived for 3 months and reached stages of neuronal and neuroglial maturation similar to controls. Both fetal spinal cord and brain were successful as implants, had delayed differentiation, and formed complex neuropils. The zone of overlapping interface of the donor and host is an anatomical indication of physiological and functional integration.     

Immunohistochemical demonstration of serotonin neurons in autonomic regions of the rat spinal cord

The immunohistochemical distribution of serotonin neurons in normal and transected spinal cords of rats was examined. Intraspinal serotonin neurons were immunostained as far rostral and caudal as T3 and Co1, respectively. All serotonin neurons were located in lamina VII and X, and most were located in spinal autonomic areas. Both bipolar and multipolar neurons were observed with many of the neurons oriented longitudinally to the long axis of the cord. Spinal neurons immunostained for serotonin were visible with and without L-tryptophan and monoamine oxidase inhibitor pretreatment.     

Transplantation of cultured fetal spinal cord grafts, grown on a histocompatible substrate, into adult spinal cord

Cell suspensions from 14-day gestation rat spinal cord can be successfully cultured on collagen gels containing laminin. After 7 and 14 days in culture the gels were removed from the dish and slices of gel with cultured cells were transplanted into the dorsal column of adult rats. Thirty days later there was no evidence of the gel. However, grafted neurons with well-developed organelles, axons, dendrites, axosomatic and axodendritic synapses were observed in the white matter of the host dorsal columns. Oligodendrocytes and astrocytes were also observed in the graft. This histocompatible substrate for culturing fetal CNS is a mechanism for transplanting cultured CNS cells as grafts of known maturity and synaptic organization into adult host CNS.     

Growth, differentiation, and viability of fetal rat cortical and spinal cord implants into adult rat spinal cord

Successful transplantation of the fetal brain into adult host brain has been accomplished. These studies explore the growth, differentiation, and viability of E11, E12, and E15 rat fetal cortex and fetal spinal cord implantation into the spinal cord of adult rats (donor and host, Sprague-Dawley). Under deep Chloropent anesthesia, 70 rats had 1-mm cubes of fetal cortex inserted with pressure or by stylus injection subpially between the dorsal horn and dorsal column (left side), or implantation of whole segments of fetal spinal cord. Animals were prepared for light microscopy 14 and 21 days and 1, 2, and 3 months later. Implants by both fetal tissues had a 69% survival rate. The younger the fetal implant the higher the success of the implant (E11 greater than E15). The diameter of fetal spinal cord implants reached the diameter of control postnatal animals after 30 days. The implants not only increased in mass (up to 7-fold in some cases) but differentiated and matured (apolar, unipolar, bipolar, and multipolar) neurons were observed one to three months postimplantation. By 30 days postimplantation, fetal neurons had large, often crenated nuclei, with a large single prominent nucleolus. The most successful implants were the young E11 fetal spinal cord into the adult host spinal cord. These implants represent an initial successful transplantation of fetal spinal cord into adult spinal cord.     

大鼠脊髓损伤后Nogo-A表达变化的免疫组织化学研究

目的观察大鼠脊髓损伤后不同时间点Nogo—A蛋白在脊髓的表达变化。方法大鼠分脊髓损伤组、假手术组和正常对照组。损伤动物存活1d、3d、7d后，分别进行Nogo—A抗体的免疫组织化学染色。结果损伤部位的灰质神经元和白质少突胶质细胞均呈明显的Nogo—A免疫阳性反应，随着损伤后存活时间的延长，两者的阳性反应细胞相对染色强度及数量均逐渐下降。结论脊髓损伤后，Nogo—A在灰质神经元有表达，其表达相对强度和表达细胞数量先明显增加，随后逐渐减少，与少突胶质细胞的表达变化相似。     

Astrocytes in rat fetal cerebral cortical homografts following implantation into adult rat spinal cord

The present experiment examines astrocytes in fetal cerebral cortical homografts to adult rat spinal cords. The purpose of this study is to determine if astrocytes are structurally organized within the graft. Also, the presence or absence of astrogliosis may be an indicator of the metabolic status of the graft. Embryonic cerebral cortex was taken at 14 days gestational age and transplanted into adult spinal cord at the level of the sixth thoracic vertebra. The homografts were examined at the light and electron microscopic levels from 7 days postimplantation (PI) to 6 months PI with glial fibrillary acidic protein antiserum which is a specific immunohistochemical marker for astrocytes. At 7 days PI, immunoreactive astrocytes were present only at the periphery of the graft and appeared to be associated with blood vessels. By 30 days PI, normal protoplasmic astrocytes were present throughout the graft. No hypertrophied astrocytes are present at 30 days PI, but the numerical density of astrocytes is greater than that of normal cerebral cortical gray matter. Fibrous astrocytes are present in the periphery of the implant and many of these astrocytes extended their processes between the host and the graft. Occasional glial scarring is observed between the gray matter of the host and graft, but generally no glial scar occurred in the interface between the graft and the host gray matter. By 45 days PI, hypertrophied astrocytes can be seen in the graft, but are confined in this age group to perivascular regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Localization of cholecystokininlike immunoreactivity in the rat spinal cord,with particular reference to the autonomic innervation of the pelvic organs

The distribution of cholecystokinin in the spinal cord was investigated by immunohistochemistry. Throughout the length of the spinal cord cholecystokinin immunoreactivity was found in laminae I and II, in the spinal re-ticular nucleus, and in the surroundings of the central canal. On the basis of the cholecystokinin pattern lamina II could be divided into a dorsal and ventral part. In the lumbar and sacral spinal cord additional terminal fields of cholecystokinin immunoreactive boutons unique to these levels were found. They corresponded to the intermediolateral nucleus and to the medial lumbar sympathetic nucleus dorsal to the central canal in the first and second lumbar segment. Also the intermediolateral nucleus in L₆–S₁ received a dense cholecystokinin positive input. Moreover, the area surrounding the central canal in L₆–S₁, contained many cholecystokinin immunoreactive structures. Combined retrograde tracing and immunocytochemistry revealed that the two cholecystokinin terminal fields characteristic for L₁–L₂ and that sur-rounding the intermediolateral nucleus in L₆–S₁ were situated corresponding to preganglionic neurons innervating pelvic organs through the hypo-gastric nerve or the pelvic nerves. It thus appears that the unique lumbosacral cholecystokinin is related to nuclei influencing pelvic structures, pointing to a special need for regulation of the organs involved in evacuation and sexual functions. Moreover, it is demonstrated that the caudal part of the spinal sympathetic system differs from the more cranial part with respect to type of afferent connections. The origin of the spinal cholecystokinin was investigated and it was found that neither complete transection of the spinal cord nor ipsilateral sectioning of three or four dorsal roots induced visible changes in the cholecystokinin staining pattern. Treatment of the caudal spinal cord with colchicine revealed the presence of cholecystokinin immunoreactive neurons in the intermediate gray, at the lateral border of the dorsal horn, in the dorsal horn proper, and in the substantia gelatinosa. These findings indicate that the majority of spinal cholecystokinin has a spinal origin.     

Synaptic remodeling in mouse motor cortex after spinal cord injury

Spinal cord injury dramatically blocks information exchange between the central nervous system and the peripheral nervous system. The resulting fate of synapses in the motor cortex has not been well studied. To explore synaptic reorganization in the motor cortex after spinal cord injury, we established mouse models of T12 spinal cord hemi-section and then monitored the postsynaptic dendritic spines and presynaptic axonal boutons of pyramidal neurons in the hindlimb area of the motor cortex in vivo. Our results showed that spinal cord hemisection led to the remodeling of dendritic spines bilaterally in the motor cortex and the main remodeling regions changed over time. It made previously stable spines unstable and eliminated spines more unlikely to be re-emerged. There was a significant increase in new spines in the contralateral motor cortex. However, the low survival rate of the new spines demonstrated that new spines were still fragile. Observation of presynaptic axonal boutons found no significant change. These results suggest the existence of synapse remodeling in motor cortex after spinal cord hemi-section and that spinal cord hemi-section affected postsynaptic dendritic spines rather than presynaptic axonal boutons. This study was approved by the Ethics Committee of Chinese PLA General Hospital, China(approval No. 201504168 S) on April 16, 2015.     

Acrylic hydrogel implants after spinal cord lesion in the adult rat

Abstract

Acrylic hydrogels, like the polymer of 2-hydroxyethyl methacrylate, are biocompatible, mechanically stable, porous materials that can be coated with collagen or laminin acting as bioadhesive substrates. Poly- 2-hydroxyethyl methacrylate sponges have been proposed for restoring the anatomical continuity of damaged neural structures. In the present work, the ability of poly-2-hydroxyethylmethacrylate sponges to provide the injured spinal cord neurons with a conductive substrate for their regenerating axons was investigatedin 32 adultWistar rats. Collagen impregnated poly-2-hydroxyethylmethacrylatesponges were implanted into suction cavities of the dorsal funiculus of the spinal cord. Two to four months after implantation, the spinal cord was removed and processed for histology, and S100 and GFAP immunohistochemistry. To study axonal regeneration into the sponge, the spinal cord or the sensorimotor cortex were injected with 0.05–0.1 ml of an 8% solution of lectin-conjugated horseradish peroxidase or 10% dextran tetramethylrhodamine. The fibroglial reaction, accumulation of mononuclear cells, and angiogenesis at the interface between the spinal cord and the sponge were minimal. Cystic cavitation in the spinal cord was virtually absent. Anterograde labeled axons were seen to penetrate and to elongate the full length of the sponge. These results demonstrate that poly-2-hydroxyethylmethacrylate sponges represent a safe supportive material for regenerating spinal cord axons.     

Transplantation of fetal spinal cord tissue into the chronically injured adult rat spinal cord

Transplants of fetal central nervous system (CNS) tissue into the acutely injured rat spinal cord have been demonstrated to differentiate and partially integrate with the adjacent host neuropil. In the present study, we examined the potential for applying a transplantation approach to chronic spinal cord lesions. In particular, we were interested in learning whether host-graft fusion would be adversely affected by an advanced histopathology characterized in part by glial scar formation. Hemisection cavities were prepared at lumbar levels of the adult rat spinal cord 2-7 weeks prior to the transplantation of spinal cord tissue obtained from 14-day rat fetuses. Graft survival, differentiation, and integration with the host spinal cord were subsequently evaluated by light microscopic techniques at post-transplantation intervals of 1-6 months. Immunocytochemistry was also employed to examine the extent of astrocytic scar formation at the host-graft interface and serotoninergic innervation of the grafts. In some other cases, anterograde and retrograde transport of wheat germ agglutinin-conjugated horseradish peroxidase was used to determine whether axonal projections were formed between the host spinal cords and grafts. By 2 weeks after injury the initial lesion cavities were surrounded by a continuous astrocytic scar which remained intact for at least 7 weeks after injury in nongrafted control animals. In other animals, transplantation into these advanced lesions resulted in well-differentiated grafts with a 90% long-term survival rate. Although dense gliosis was still present along the lesion surfaces of the recipient spinal cord, foci of confluent host-graft neuropil were observed where interruptions in the scar had occurred. Donor tissue integrated most often with the host spinal cord at interfaces with host gray matter; however, some implants also exhibited sites of fusion with damaged host white matter. Thus, some regions of confluent graft and host neuropil could be routinely identified, despite the presence of a dense glial scar along the walls of the chronic lesion site at the time of transplantation. Anterograde and retrograde tract-tracing results suggested that some axonal projections into these grafts had originated from host neurons located immediately adjacent to the donor-recipient interface. In addition, immunocytochemistry revealed some host serotoninergic axons (presumably of supraspinal origin) traversing nongliotic interfaces. The results of this study raise the possibility that grafted fetal CNS tissue has a capacity for stimulating partial regression of an established glial scar.(ABSTRACT TRUNCATED AT 400 WORDS)     

Systemic injections of lipopolysaccharide accelerates myelin phagocytosis during Wallerian degeneration in the injured mouse spinal cord

The phagocytic cell response within the injured spinal cord is inefficient, allowing myelin debris to remain for prolonged periods of time within white matter tracts distal to the injury. Several proteins associated with this degenerating myelin are inhibitory to axon growth and therefore prevent severed axons from regenerating. Inflammatory agents such as lipopolysaccharide (LPS) can stimulate both the migration and phagocytic activity of macrophages. Using in situ hybridization, we found that the expression of the LPS membrane receptor, CD14, was enhanced in the mouse dorsal column following a dorsal hemisection. Double labeling studies showed that microglia and macrophages are the two major cell types expressing CD14 mRNA following spinal cord injury (SCI). We therefore tested whether systemic injections of LPS would increase the number and phagocytic activity of macrophages/microglia in the ascending sensory tract (AST) of the mouse dorsal column following a dorsal hemisection. Mice were treated daily via intraperitoneal injections of either LPS or phosphate-buffered saline (PBS). At 7 days post-SCI, greater numbers of activated mononuclear phagocytes were present in the AST undergoing Wallerian degeneration (WD) in LPS-treated animals compared with controls. Animals treated with LPS also exhibited greater Oil Red O staining, which is specific for degenerating myelin and macrophages phagocytosing myelin debris. Myelin clearance was confirmed at 7 days using Luxol Fast Blue staining and on toluidine blue-stained semi-thin sections. These results indicate that it is possible to manipulate the innate immune response to accelerate myelin clearance during WD in the injured mouse spinal cord.     

Ultrastructural organization of regenerated adult dorsal root axons within transplants of fetal spinal cord.

It has previously been demonstrated that the severed central branches of adult mammalian dorsal root ganglion cells regenerate into transplants of fetal spinal cord. The aim of this study was to determine whether these regenerating axons form synapses, and, if they do, to characterize them morphologically. Embryonic day 14 or 15 spinal cord was transplanted into the lumbar enlargement of adult Sprague-Dawley rats, and the L4 or L5 dorsal root was cut and then juxtaposed to the transplant. One to 3 months later the regenerated dorsal roots were labeled by anterograde filling with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) or by immunocytochemistry for calcitonin gene-related peptide (CGRP). Dorsal root labeling with WGA-HRP demonstrated that regenerated axon terminals made synaptic contacts within transplants, and stereological electron microscopic analysis demonstrated that CGRP-immunoreactive axon terminals occupied an average of 9% of the neuropil within 2 mm of the dorsal root-transplant interface. The majority of synapses were axodendritic, but a significant percentage were axosomatic or axoaxonic. Since axoaxonic synapses were observed in transplants in which both pre- and postsynaptic profiles of axoaxonic synapses were labeled for CGRP, some regenerated axons apparently form synapses with each other. Approximately 90% of synaptic contacts were simple, 9% were complex, and 25% of the complex terminals were immunopositive for CGRP. Glia occupied 25% of the neuropil within 1 mm of the dorsal root-transplant interface, but only 6% of the neuropil 1-2 mm from the interface. We also performed a stereological analysis of the neuropil in lamina I. The area fractions of neuropil occupied by myelinated axons, perikarya, and dendrites were similar in transplants and in lamina I. However, the area fraction occupied by unmyelinated axons was significantly smaller in transplants, and the area fraction occupied by axon terminals was significantly larger in transplants compared with lamina I. Regenerated CGRP-immunoreactive synaptic terminals in transplants were significantly larger than in normal lamina I, and their synaptic contact length was also increased, suggesting that a compensatory mechanism for increasing synaptic efficiency might occur within the transplants. Synaptic density, however, was significantly reduced in transplants, indicating a smaller number of synaptic terminals per unit area. In lamina I, as in the transplant, most synapses were axodendritic, but the percentage of axosomatic and axoaxonic terminals was lower in lamina I than in the transplants.(ABSTRACT TRUNCATED AT 400 WORDS)     

Regrowth of axons into the distal spinal cord through a Schwann-cell-seeded mini-channel implanted into hemisected adult rat spinal cord

Schwann cells (SCs) have been shown to be a key element in promoting axonal regeneration after being grafted into the central nervous system (CNS). In the present study, SC-supported axonal regrowth was tested in an adult rat spinal cord implantation model. This model is characterized by a right spinal cord hemisection at the eighth thoracic segment, implantation of a SC-containing mini-channel and restoration of cerebrospinal fluid circulation by suturing the dura. We demonstrate that a tissue cable containing grafted SCs formed an effective bridge between the two stumps of the hemicord 1 month after transplantation. Approximately 10 000 myelinated and unmyelinated axons (1 : 9) per cable were found at its midpoint. In addition to propriospinal axons and axons of peripheral nervous system (PNS) origin, axons from as many as 19 brainstem regions also grew into the graft without additional treatments. Most significantly, some regenerating axons in the SC grafts were able to penetrate through the distal graft-host interface to re-enter the host environment, as demonstrated by anterograde axonal labelling. These axons coursed toward, and then entered the grey matter where terminal bouton-like structures were observed. In channels containing no SCs, limited axonal growth was seen within the graft and no axons penetrated the distal interface. These findings further support the notion that SCs are strong promotors of axonal regeneration and that the mini-channel model may be appropriate for further investigation of axonal re-entry, synaptic reconnection and functional recovery following spinal cord injury.     

经单侧半椎板切除髓内海绵状血管瘤

目的探讨脊髓髓内海绵状血管瘤的出血性损伤风险、临床特征以及经单侧半椎板切除髓内海绵状血管瘤的手术技巧。方法回顾性分析11例髓内海绵状血管瘤病人的病历资料。均经单侧半椎板切除肿瘤。采用统计学分析，在性别分布、平均年龄、年出血率等方面与同期颅内（145例）、脑干（61例）海绵状血管瘤进行比较。术前Frankel分级D级8例，C级2例，A级1例。结果本组女性7例，男性4例．女性与男性之比高于颅内（80：65）和脑干（33：28）海绵状血管瘤；年出血率为2．8％／病人，稍低于颅内（3．3％）和脑干（3．1％）海绵状血管瘤。病变均获全切：术后随访期内8例神经系统症状改善（Frankel分级D级升到E级6例，C级升到D级2例）．3例临床症状无变化。结论脊髓髓内海绵状血管瘤应全切以防复发和再出血；选择微侵袭的半椎板入路，以及术中采用体感诱发电位监护．是取得满意结果、预防附加损伤的关键．     

脊髓海绵状血管瘤的显微外科治疗

目的总结脊髓海绵状血管瘤的手术经验。方法回顾性分析39例海绵状血管瘤病人的临床表现、术前MRI表现、术中所见、手术切除情况、术后MRI表现及随访结果。均在显微镜下行手术治疗,根据肿瘤与脊髓有无明确边界,决定肿瘤切除的程度。手术前后采用McCormick分级评价脊髓功能。结果镜下见肿瘤有明确边界者行手术全切除,共34例;肿瘤有相对边界但不明确者仅行近全切除,共4例;肿瘤无边界且病人术前功能较差者行部分切除,计1例。病理证实均为海绵状血管瘤。术后McCormick分级改善30例,无变化5例,加重4例。结论MRI是脊髓海绵状血管瘤术前诊断最有效的方法;手术全切除病变是最主要的治疗方法,有症状者应积极行手术治疗。     

Experimental studies on spinal cord injuries in the last fifteen years

Abstract

Experimental studies on spinal cord (SC) injuries published from 1975 to 1989 in some of the most widely circulating neurosurgical journals were reviewed. The relatively large number of animal species utilized as well as the intensely variable dynamic or static methods employed to induce SC injury represent elements of confusion more than objective necessities in this field of research. In fact, the objective of SC injury research should be to solve the problem of severe SC injuries by either preventing and/or repairing SC damage, rather than looking for modalities to provoke a large spectrum of SC injuries with the result of establishing a correlation between for example, the clinical picture and trauma magnitude. It should be time to study all variables and treatments mainly in only one experimental model. The rat with a permanent paraplegia should represent such a model; the abdominal aorta occlusion for 45 minutes, distal to the renal arteries in rabbits should be the experimental model of choice for ischaemia. If a significant result, such as reversing permanent paraplegia, were obtained in rats, it would be logical to repeat the study in higher mammals and if successful' in humans. For the last decade of this century it is necessary to further study all the mechanisms implied in secondary SC damage as well as to attempt to repair definitive SC damage by using grafts and enhancing the potential regenerative ability of the SC with known and new growth factors. Presently, methylprednisolone, dexametasone, thiopental, naloxone, and hypothermia seem to have some clinical potentials that require studies in humans.