Endoplasmic reticulum stress-induced apoptosis in the penumbra aggravates secondary damage in rats with traumatic brain injur y

Neuronal apoptosis is mediated by intrinsic and extrinsic signaling pathways such as the membrane-mediated, mitochondrial, and endo-plasmic reticulum stress pathways. Few studies have examined the endoplasmic reticulum-mediated apoptosis pathway in the penumbra after traumatic brain injury, and it remains unclear whether endoplasmic reticulum stress can activate the caspase-12-dependent apoptotic pathway in the traumatic penumbra. Here, we established rat models of lfuid percussion-induced traumatic brain injury and found that protein expression of caspase-12, caspase-3 and the endoplasmic reticulum stress marker 78 kDa glucose-regulated protein increased in the traumatic penumbra 6 hours after injury and peaked at 24 hours. Furthermore, numbers of terminal deoxynucleotidyl transferase-mediat-ed dUTP nick end labeling-positive cells in the traumatic penumbra also reached peak levels 24 hours after injury. These ifndings suggest that caspase-12-mediated endoplasmic reticulum-related apoptosis is activated in the traumatic penumbra, and may play an important role in the pathophysiology of secondary brain injury.     

Apelin-13 as a novel target for intervention in secondar y injur y after traumatic brain injur y

The adipocytokine, apelin-13, is an abundantly expressed peptide in the nervous system. Apelin-13 protects the brain against ischemia/reperfusion injury and attenuates traumatic brain injury by suppressing autophagy. However, secondary apelin-13 effects on traumatic brain injury-induced neural cell death and blood-brain barrier integrity are still not clear. Here, we found that apelin-13 signiifcantly de-creases cerebral water content, mitigates blood-brain barrier destruction, reduces aquaporin-4 expression, diminishes caspase-3 and Bax expression in the cerebral cortex and hippocampus, and reduces apoptosis. These results show that apelin-13 attenuates secondary injury after traumatic brain injury and exerts a neuroprotective effect.     

Melatonin prevents brain oxidative stress induced by obstructive jaundice in rats

The aim of the study was to analyze the impact of melatonin on brain oxidative stress in experimental biliary obstruction. Cholestasis was done by a double ligature and section of the extrahepatic biliary duct. Melatonin was injected intraperitoneally (500 microg/kg/day). Malondialdehyde (MDA), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) contents were determined in the brain tissue. Biliary obstruction raised MDA and reduced GSH contents in the cortex, cerebellum, and hypothalamus areas. Moreover, the scavenger enzyme activity significantly dropped in all areas of the brain. Melatonin drastically reduced MDA concentration and enhanced GSH concentration, as well as all antioxidant enzyme activity in all brain areas obtained from the bile duct-ligated animals. In conclusion, the treatment with melatonin decreased lipid peroxidation and recovered the antioxidant status in the brain from cholestatic animals.     

Neuroprotective effects of cold-inducible RNA-binding protein during mild hypothermia on traumatic brain injur y

Cold-inducible RNA-binding protein(CIRP), a key regulatory protein, could be facilitated by mild hypothermia in the brain, heart and liver. This study observed the effects of mild hypothermia at 31 ± 0.5℃ on traumatic brain injury in rats. Results demonstrated that mild hypothermia suppressed apoptosis in the cortex, hippocampus and hypothalamus, facilitated CIRP m RNA and protein expression in these regions, especially in the hypothalamus. The anti-apoptotic effect of mild hypothermia disappeared after CIRP silencing. There was no correlation between mitogen-activated extracellular signal-regulated kinase activation and CIRP silencing. CIRP silencing inhibited extracellular signal-regulated kinase-1/2 activation. These indicate that CIRP inhibits apoptosis by affecting extracellular signal-regulated kinase-1/2 activation, and exerts a neuroprotective effect during mild hypothermia for traumatic brain injury.     

大剂量维生素C和维生素E对急性颅脑损伤病人神经损伤、神经营养及氧化应激的影响

目的 探讨大剂量维生素C和维生素E对急性颅脑损伤病人神经损伤、神经营养及氧化应激的影响。方法 2018年1月至2018年11月前瞻性收集84例急性颅脑损伤并随机分为对照组（n=42,接受常规治疗）和观察组（n=42,接受大剂量维生素C和维生素E联合常规治疗）。治疗前、治疗后4、7 d,采用酶联免疫吸附法测定血清神经损伤指标[包括神经元特异性烯醇化酶（NSE）、S100蛋白、脑红蛋白（NGB）、泛素羧基末端水解酶L1（UCH-L1））、神经营养指标[包括神经营养因子-α（NTF-α）、脑源性神经营养因子（BDNF）、神经生长因子（NGF）、胰岛素样生长因子-1（IGF-I）,采用放射免疫沉淀法测定氧化应激指标[包括超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GPx）、过氧化氢酶（CAT）、丙二醛（MDA）、晚期氧化蛋白产物（AOPP）]。结果 治疗后4、7 d,两组血清NSE、S100B、NGB、UCH-L1、MDA、AOPP含量均显著降低（P<0.05）,血清NTF-α、BDNF、NGF、IGF-I、SOD、GPx、CAT含量均显著增高（P<0.05）,而且,观察组均明显优于对照组（P<0.05）。结论 大剂量维生素C和维生素E治疗能够减轻急性颅脑损伤病人神经损伤程度、氧化应激反应并改善神经营养状态。     

Effect of oxidative stress in rostral ventrolateral medulla on sympathetic hyperactivity after traumatic brain injury

Sympathetic hyperactivity occurs in a subgroup of patients after traumatic brain injury (TBI). The rostral ventrolateral medulla (RVLM) is a key region for the activity of sympathetic nervous system. Oxidative stress in the RVLM is proved to be responsible for the increased level of sympathetic activity in animal models of hypertension and heart failure. In this study, we investigated whether oxidative stress in the RVLM contributed to the development of sympathetic hyperactivity after TBI in rats. Model of diffuse axonal injury was induced using Sprague‐Dawley rats, and level of mean arterial pressure (MAP) and plasma Norepinephrine (NE) was measured to evaluate the sympathetic activity. For the assessment of oxidative stress, expression of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) in the RVLM was determined. Microinjection of Tempol into the RVLM was performed to determine the effect of oxidative stress on sympathetic hyperactivity. According to the results, TBI led to elevated MAP and plasma NE in rats. It also induced a significantly increased level of ROS, MDA production and decreased level of SOD in the RVLM. The sympathetic activity, ROS, and MDA in the RVLM decreased significantly after microinjection of Tempol. Therefore, the present results suggested that oxidative stress in the RVLM was involved in the development of sympathetic hyperactivity following TBI.     

Breviscapine reduces neuronal injury caused by traumatic brain injury insult:partly associated with suppression of interleukin-6 expression

Breviscapine,extracted from the herb Erigeron breviscapus,is widely used for the treatment of cardiovascular diseases,cerebral infarct,and stroke,but its mechanism of action remains unclear.This study established a rat model of traumatic brain injury induced by controlled cortical impact,and injected 75 μg breviscapine via the right lateral ventricle.We found that breviscapine significantly improved neurobehavioral dysfunction at 6 and 9 days after injection.Meanwhile,interleukin-6 expression was markedly down-regulated following breviscapine treatment.Our results suggest that breviscapine is effective in promoting neurological behavior after traumatic brain injury and the underlying molecular mechanism may be associated with the suppression of interleukin-6.     

Increase in blood-brain barrier permeability, oxidative stress, and activated microglia in a rat model of blast-induced traumatic brain injury

Traumatic brain injury (TBI) as a consequence of exposure to blast is increasingly prevalent in military populations, with the underlying pathophysiological mechanisms mostly unknown. In the present study, we utilized an air-driven shock tube to investigate the effects of blast exposure (120 kPa) on rat brains. Immediately following exposure to blast, neurological function was reduced. BBB permeability was measured using IgG antibody and evaluating its immunoreactivity in the brain. At 3 and 24 hr postexposure, there was a transient significant increase in IgG staining in the cortex. At 3 days postexposure, IgG immunoreactivity returned to control levels. Quantitative immunostaining was employed to determine the temporal course of brain oxidative stress following exposure to blast. Levels of 4-hydroxynonenal (4-HNE) and 3-nitrotyrosine (3-NT) were significantly increased at 3 hr postexposure and returned to control levels at 24 hr postexposure. The response of microglia to blast exposure was determined by autoradiographic localization of (3) H-PK11195 binding. At 5 days postexposure, increased binding was observed in the contralateral and ipsilateral dentate gyrus. These regions also displayed increased binding at 10 days postexposure; in addition to these regions there was increased binding in the contralateral ventral hippocampus and substantia nigra at this time point. By using antibodies against CD11b/c, microglia morphology characteristic of activated microglia was observed in the hippocampus and substantia nigra of animals exposed to blast. These results indicate that BBB breakdown, oxidative stress, and microglia activation likely play a role in the neuropathology associated with TBI as a result of blast exposure.     

Dose-dependent neuroprotective effect of enoxaparin on cold-induced traumatic brain injury

Recent evidence exists that enoxaparin can reduce brain injury because of its anticoagulant activity. To investigate the potential therapeutic effect of enoxaparin on cold-induced traumatic brain injury, at 20 minutes after modeling, male BALB/c mouse models of cold-induced traumatic brain injury were intra-peritoneally administered 3 and 10 mg/kg enoxaparin or isotonic saline solution. Twenty-four hours later, enoxaparin at 10 mg/kg greatly reduced infarct volume, decreased cell apoptosis in the cortex and obviously increased serum level of total antioxidant status. By contrast, administration of enoxaparin at 3 mg/kg did not lead to these changes.These findings suggest that enoxaparin exhibits neuroprotective effect on cold-in-duced traumatic brain injury in a dose-dependent manner.     

Syringaldehyde exerts neuroprotective effect on cerebral ischemia injury in rats through anti-oxidative and anti-apoptotic properties

There are few studies on the neuroprotective effects of syringaldehyde in a rat model of cerebral ischemia. The study aimed to elucidate the mechanisms underlying the neuroprotective effects of syringaldehyde on ischemic brain cells. Rat models of cerebral ischemia were intraperitoneally administered syringaldehyde. At 6 and 24 hours after syringaldehyde administration, cell damage in the brain of cerebral ischemia rats was obviously reduced, superoxide dismutase activity and nuclear respiratory factor 1 expression in the brain tissue were markedly increased, malondi-adehyde level was obviously decreased, apoptosis-related cysteine peptidase caspase-3 and -9 immunoreactivity was obviously decreased, and neurological function was markedly improved. These ifndings suggest that syringaldehyde exerts neuroprotective effects on cerebral ischemia injury through anti-oxidation and anti-apoptosis.     

右正中神经电刺激对重型颅脑损伤患者脑血流灌注影响的SPECT-CT观察

目的研究SPECT-CT融合机检测重型颅脑损伤昏迷患者行右正中神经电刺激前后脑血流灌注变化情况。方法选择我院重型颅脑损伤患者50例作为研究对象,伤后2周持续昏迷,接受右正中神经电刺激治疗。治疗前后7 d均进行SPECT-CT检查,评价脑血流灌注变化的情况。利用MATLAB和SPM软件对检测结果进行分析处理,得到昏迷患者的脑皮层血流及健康成人的比较值,使用区域分析法进行脑皮层分析,丘脑及脑干部位的血流灌注增加特征变化,利用图形重建迭加技术获得脑表面血流灌注增加值.并测量GCS和GOS评分,伤后1年作GOS预后评估。结果电刺激治疗后,患者脑血流有明显改善,血流灌注增加表现,GOS评分较电刺激后评分升高。结论右正中神经电刺激技术可以改善脑干血流灌注状况。     

香芹酚通过抑制脑水肿与氧化应激反应保护大鼠 颅脑损伤

目的 探讨香芹酚对大鼠颅脑损伤（TBI）的保护作用及其机制。方法 SD大鼠50只,随机分为5组:假手术组、模型组、低剂量香芹酚（10 mg/kg）组、中剂量香芹酚（20 mg/kg）组、高剂量香芹酚（40 mg/kg）组,每组10只。Feeney氏自由落体法制备TBI模型,造模后1、3、7 d采用改良神经功能损害程度评分（mNSS）评估神经功能,干湿法测定脑组织含水量;ELISA法检测氧化应激因子丙二醛（MDA）、超氧化物歧化酶（SOD）、谷胱甘肽（GSH）、过氧化氢酶（CAT）以及化学定量法检测一氧化氮（NO）含量及一氧化氮合酶（NOS）活性。结果 香芹酚能显著改善大鼠TBI后神经功能,显著减轻TBI后脑水肿,显著降低损伤脑组织MDA、NO和NOS含量,显著增加损伤脑组织SOD、CAT和GSH含量。结论 香芹酚可通过减轻大鼠TBI后脑水肿、抑制氧化应激从而发挥神经保护作用。     

Pulsed arterial spin labeling effectively and dynamically observes changes in cerebral blood flow after mild traumatic brain injury

Cerebral blood flow is strongly associated with brain function, and is the main symptom and diagnostic basis for a variety of encephalopathies. However, changes in cerebral blood flow after mild traumatic brain injury remain poorly understood. This study sought to observe changes in cerebral blood flow in different regions after mild traumatic brain injury using pulsed arterial spin labeling. Our results demonstrate maximal cerebral blood flow in gray matter and minimal in the white matter of patients with mild traumatic brain injury. At the acute and subacute stages, cerebral blood flow was reduced in the occipital lobe, parietal lobe, central region, subcutaneous region, and frontal lobe. Cerebral blood flow was restored at the chronic stage. At the acute, subacute, and chronic stages, changes in cerebral blood flow were not apparent in the insula. Cerebral blood flow in the temporal lobe and limbic lobe diminished at the acute and subacute stages, but was restored at the chronic stage. These findings suggest that pulsed arterial spin labeling can precisely measure cerebral blood flow in various brain regions, and may play a reference role in evaluating a patient's condition and judging prognosis after traumatic brain injury.     

Proteomic identification of nitrated brain proteins in traumatic brain-injured rats treated postinjury with gamma-glutamylcysteine ethyl ester: insights into the role of elevation of glutathione as a potential therapeutic strategy for traumatic brain injury

Traumatic brain injury (TBI) occurs suddenly and has damaging effects to the brain that are dependent on the severity of insult. Symptoms can be mild, moderate, or severe. Oxidative damage is associated with traumatic brain injury through reactive oxygen/nitrogen species production. One such species, peroxynitrite, is elevated in TBI brain tissue (Orihara et al. [2001] Forensic Sci. Int. 123:142-149; Deng et al. [2007] Exp. Neurol. 205:154-165). Peroxynitrite can react with carbon dioxide and decompose to produce NO(2) and carbonate radicals, which in turn can lead to 3-nitrotyrosine, an index of protein nitration. Gamma-glutamylcysteine ethyl ester (GCEE) is an ethyl ester moiety of gamma-glutamylcysteine, an agent that up-regulates glutathione (GSH) production in brain (Drake et al. [2002] J. Neurosci. Res. 68:776-784). Many preclinical studies of TBI have employed pretreatment of animals with proposed beneficial agents prior to the injury itself. However, in the real world of TBI, treatment begins postinjury. Hence, insights into agents that improve outcome following injury are desperately needed. This study is one of the first to investigate a potential GSH-based therapy for TBI postinjury. Protein carbonyls, an index of protein oxidation, were significantly elevated in brain of animals subjected to TBI. However, if, after TBI, GCEE was administered i.p., protein carbonyl levels were significantly reduced. Similarly, 3-nitrotyrosine levels were elevated in brain following TBI but significantly decreased following TBI if GCEE was administered i.p. Redox proteomics analysis showed that several brain proteins were nitrated after TBI. However, if GCEE was given i.p. following TBI, many of these proteins were protected from nitration. The results are encouraging and are discussed with reference to potential therapeutic strategies for TBI involving elevated GSH.     

Comparison of labeling methods and time course of traumatic brain injury-induced cell death in mice

BACKGROUND:Various molecular mechanisms of cell death following traumatic brain injury have been previously described.However,the time course of cell death remains unclear.TUNEL and Fluoro-Jade B labeling have been widely used to label apoptotic cells and neuronal degeneration.Propidium iodide (PI) functions as a biomarker of cell death in vivo.OBJECTIVE:To explore the role of PI labeling compared to TUNEL and Fluoro-Jade B staining for detecting neural cell death,and to observe time course of traumatic brain injury-induced cell death in mice.DESIGN,TIME AND SETTING:A randomized,controlled,animal experiment was performed at the Laboratory of Aging and Nervous Diseases,Soochow University from September 2007 to December 2008.MATERIALS:PI (B1221) was purchased from Sigma,USA.TUNEL kit was purchased from Roche Molecular Biochemicals,USA.Fluoro-Jade B was purchased from Chemicon,USA.METHODS:A total of 70 healthy,male,Kunming mice were randomly assigned to sham-surgery (n = 5) and model (n = 65) groups.Traumatic brain injury was established using the controlled cortical impact method.PI was intraperitoneally injected at 1 hour prior to animal sacrifice.MAIN OUTCOME MEASURES:TUNEL,Fluoro-Jade B,and Pl-positive cells were quantified using a double-labeling method to determine the time course of traumatic brain injury-induced cell death.RESULTS:PI labeled cells in an earlier phase of cell death than TUNEL and Fluoro-Jade B labeling.Pl-positive cells were observed immediately following injury,and the numbers rapidly increased in injured brain areas at 1 hour,peaked at 24-48 hours,and subsequently decreased at 3-21 days post-injury.TUNEL-labeled cells were significantly increased at 12 hours,while Fluoro-Jade B-labeled cells were increased at 6 hours after injury,with cells still visible at 6-48 hours post-injury.Moreover,a greater number of Pl-positive cells were observed compared to TUNEL- and Fluoro-Jade B-labeled cells.CONCLUSION:PI labeling is more sensitive and reliable than TUNEL and Fluoro-Jade B staining for detecting cell death following traumatic brain injury.Moreover,PI labeling can function as a reliable marker to estimate the entire time course of cell death.     

The potential of neural transplantation for brain repair and regeneration following traumatic brain injury

Traumatic brain injury is a major health problem worldwide. Currently, there is no effective treatment to improve neural structural repair and functional recovery of patients in the clinic. Cell transplantation is a potential strategy to repair and regenerate the injured brain. This review article summarized recent de-velopment in cell transplantation studies for post-traumatic brain injury brain repair with varying types of cell sources. It also discussed the potential of neural transplantation to repair/promote recovery of the injured brain following traumatic brain injury.     

骨髓间质干细胞移植对大鼠颅脑损伤后氧化应激的影响

目的观察骨髓间质干细胞移植对大鼠外伤性脑损伤的治疗效应和对大鼠颅脑损伤后氧化应激的影响。方法体外分离培养MSCs;建立大鼠TBI模型;经颈内动脉移植MSCs,观察大鼠神经功能的改善状况和两组大鼠脑组织内氧化应激指标的差异。结果MSCs在体外可长期培养扩增,生物学特性稳定;经颈动脉移植4周后,移植治疗的大鼠其神经功能状况改善较好。与对照组相比较,实验组大鼠脑组织内SOD的活性较高,羟自由基的含量较低。结论移植MSCs对TBI所造成的大鼠神经功能缺损有一定的治疗效应。而移植MSCs后能上调脑组织的抗氧化能力,这可能是产生治疗效应的机制之一。     

[Gly14]-Humanin减轻大鼠颅脑外伤后氧化应激及细胞凋亡

目的探讨[Gly14]-Humanin(HNG)对大鼠颅脑外伤后脑组织超氧化物歧化酶(SOD)、丙二醛(MDA)、谷胱甘肽(GSH)和细胞凋亡的影响。方法 135只SD大鼠分为空白组(n=45)、对照组(n=45)及HNG组(n=45),其中对照组及HNG组建立颅脑外伤模型后前者予右侧股静脉注射生理盐水2 m L/kg,后者则予HNG 2μL/kg,此后各组每24 h予1次等量生理盐水/HNG,直至大鼠被处死;而空白组不予任何处理。根据处死时间随机分为1 h、3 d和7 d共3个亚组,每亚组各15只。比较损伤灶周围脑组织MDA、SOD、GSH含量水平及细胞凋亡情况。结果 HNG组大鼠脑组织中MDA含量水平及凋亡细胞计数在损伤后1 h即升高,3 d达到最高值,后开始降低,但7 d时仍高于损伤后1 h水平,均显著低于同一时间点的对照组及空白组(P均0.05);相反,SOD活性在损伤后迅速降低,3 d达到最低值,随后逐渐上升,但7 d时仍低于损伤后1 h水平,均显著高于同一时间点的对照组及空白组(P均0.05);GSH变化规律与SOD基本一致,与各时间点的对照组比较亦有显著性(P均0.05);HNG大鼠脑组织损伤后MDA含量水平与细胞凋亡数呈正相关(r=0.720,P0.05),而SOD及GSH的含量与细胞凋亡数呈负相关(r=-0.702,P0.05;r=-0.674,P0.05)。结论颅脑外伤后HNG抑制氧化应激反应,进一步减少细胞凋亡,从而发挥神经保护作用。     

Tyrosine promotes oxidative stress in cerebral cortex of young rats

Tyrosine accumulates in inborn errors of tyrosine catabolism, especially in tyrosinemia type II, where tyrosine levels are highly elevated in tissues and physiological fluids of affected patients. In tyrosinemia type II, high levels of tyrosine are correlated with eyes, skin and central nervous system disturbances. Considering that the mechanisms of brain damage in these disorders are poorly known, in the present study, we investigated whether oxidative stress is elicited by l-tyrosine in cerebral cortex homogenates of 14-day-old Wistar rats. The in vitro effect of 0.1-4.0mM l-tyrosine was studied on the following oxidative stress parameters: total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR), ascorbic acid content, reduced glutathione (GSH) content, spontaneous chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS), thiol-disulfide redox state (SH/SS ratio), protein carbonyl content, formation of DNA-protein cross-links, and the activities of the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glucose-6-phosphate dehydrogenase (G6PDH). TRAP, TAR, ascorbic acid content, SH/SS ratio and CAT activity were significantly diminished, while formation of DNA-protein cross-link was significantly enhanced by l-tyrosine in vitro. In contrast, l-tyrosine did not affect the other parameters of oxidative stress evaluated. These results indicate that l-tyrosine decreases enzymatic and non-enzymatic antioxidant defenses, changes the redox state and stimulates DNA damage in cerebral cortex of young rats in vitro. This suggests that oxidative stress may represent a pathophysiological mechanism in tyrosinemic patients, in which this amino acid accumulates.     

Endogenous adult neurogenesis and cognitive function recovery following traumatic brain injury in the rat hippocampus

BACKGROUND:Endogenous neural progenitor cells play a beneficial role for cognitive recovery following traumatic brain injury.However,there are few classification-control studies aimed at varying graded brain trauma.OBJECTIVE:To observe the effects of adult endogenous neurogenesis on cognitive function repair and regeneration of neural progenitor cells following varying graded traumatic hippocampal injury to determine the significance of endogenous neurogenesis in the repair of brain injury.DESIGN,TIME AND SETTING:A randomized,controlled,animal experiment was performed at the Key Laboratory of Injuries,Variations and Regeneration of Nervous System,Tianjin Medical University General Hospital,from February to October 2009.MATERIALS:Mouse anti-rat 5-bromodeoxyuridine (BrdU) and neuronal nuclei (NeuN) monoclonal antibodies were purchased from Millipore Corporation,USA.METHODS:A total of 45 Wistar rats were randomly assigned to three groups.Mild and severe injury groups were respectively subjected to (182 ± 2) kPa and (284 ± 4) kPa lateral fluid percussion to establish models of brain injury,and the control group was subjected to surgery with no lateral fluid percussion.MAIN OUTCOME MEASURES:Cognitive function was estimated using the Morris water maze.Proliferation,survival,and differentiation of newly generated cells in the injured hippocampus were observed through the use of immunofluorescent staining.RESULTS:At 7 days post-injury,the number of BrdU+ cells in the hippocampal dentate gyrus significantly increased in the mild and severe injury groups compared with the control group (P<0.01).At 61 days post-injury,the number of BrdU7NeuN+ cells in the hippocampal dentate gyrus was significantly greater in the mild injury group compared with the severe injury and control groups (P< 0.01).In addition,the control group exhibited the greatest proportion of surviving cells that differentiated into mature neurons compared with the injury groups (P< 0.01).Moreover,at 61 days post-injury,cognitive function in rats with mild injury recovered to normal levels,whereas the severe injury group exhibited cognitive deficits (P< 0.01).CONCLUSION:Traumatic brain injury may be a stimulation factor for proliferation of neural progenitor cells in the adult hippocampus but severe brain trauma does not lead to an increased number of newly generated cells.Endogenous adult neurogenesis repairs neurological functions to an extent.However,recovery of neurological function remains limited following severe traumatic brain injury.