Rbm8a regulates neurogenesis and reduces Alzheimer's disease-associated pathology in the dentate gyrus of 5×FAD mice

Alzheimer’s disease is a prevalent and debilitating neurodegenerative condition that profoundly affects a patient’s daily functioning with progressive cognitive decline,which can be partly attributed to impaired hippocampal neurogenesis.Neurogenesis in the hippocampal dentate gyrus is likely to persist throughout life but declines with aging,especially in Alzheimer’s disease.Recent evidence indicated that RNA-binding protein 8A(Rbm8a)promotes the proliferation of neural progenitor cells,with lower expression levels observed in Alzheimer’s disease patients compared with healthy people.This study investigated the hypothesis that Rbm8a overexpression may enhance neurogenesis by promoting the proliferation of neural progenitor cells to improve memory impairment in Alzheimer’s disease.Therefore,Rbm8a overexpression was induced in the dentate gyrus of 5×FAD mice to validate this hypothesis.Elevated Rbm8a levels in the dentate gyrus triggered neurogenesis and abated pathological phenotypes(such as plaque formation,gliosis reaction,and dystrophic neurites),leading to ameliorated memory performance in 5×FAD mice.RNA sequencing data further substantiated these findings,showing the enrichment of differentially expressed genes involved in biological processes including neurogenesis,cell proliferation,and amyloid protein formation.In conclusion,overexpressing Rbm8a in the dentate gyrus of 5×FAD mouse brains improved cognitive function by ameliorating amyloid-beta-associated pathological phenotypes and enhancing neurogenesis.

Astrocytic endothelin-1 overexpression impairs learning and memory ability in ischemic stroke via altered hippocampal neurogenesis and lipid metabolism

Vascular etiology is the second most prevalent cause of cognitive impairment globally.Endothelin-1,which is produced and secreted by endothelial cells and astrocytes,is implicated in the pathogenesis of stroke.However,the way in which changes in astrocytic endothelin-1 lead to poststroke cognitive deficits following transient middle cerebral artery occlusion is not well understood.Here,using mice in which astrocytic endothelin-1 was overexpressed,we found that the selective overexpression of endothelin-1 by astrocytic cells led to ischemic stroke-related dementia(1 hour of ischemia;7 days,28 days,or 3 months of reperfusion).We also revealed that astrocytic endothelin-1 overexpression contributed to the role of neural stem cell proliferation but impaired neurogenesis in the dentate gyrus of the hippocampus after middle cerebral artery occlusion.Comprehensive proteome profiles and western blot analysis confirmed that levels of glial fibrillary acidic protein and peroxiredoxin 6,which were differentially expressed in the brain,were significantly increased in mice with astrocytic endothelin-1 overexpression in comparison with wild-type mice 28 days after ischemic stroke.Moreover,the levels of the enriched differentially expressed proteins were closely related to lipid metabolism,as indicated by Kyoto Encyclopedia of Genes and Genomes pathway analysis.Liquid chromatography-mass spectrometry nontargeted metabolite profiling of brain tissues showed that astrocytic endothelin-1 overexpression altered lipid metabolism products such as glycerol phosphatidylcholine,sphingomyelin,and phosphatidic acid.Overall,this study demonstrates that astrocytic endothelin-1 overexpression can impair hippocampal neurogenesis and that it is correlated with lipid metabolism in poststroke cognitive dysfunction.

Adult neurogenesis:a real hope or a delusion?

Adult neurogenesis,the process of creating new neurons,involves the coordinated division,migration,and differentiation of neural stem cells.This process is restricted to neurogenic niches located in two distinct areas of the brain:the subgranular zone of the dentate gyrus of the hippocampus and the subventricular zone of the lateral ventricle,where new neurons are generated and then migrate to the olfactory bulb.Neurogenesis has been thought to occur only during the embryonic and early postnatal stages and to decline with age due to a continuous depletion of neural stem cells.Interestingly,recent years have seen tremendous progress in our understanding of adult brain neurogenesis,bridging the knowledge gap between embryonic and adult neurogenesis.Here,we discuss the current status of adult brain neurogenesis in light of what we know about neural stem cells.In this notion,we talk about the importance of intra cellular signaling molecules in mobilizing endogenous neural stem cell prolife ration.Based on the current understanding,we can declare that these molecules play a role in targeting neurogenesis in the mature brain.However,to achieve this goal,we need to avoid the undesired proliferation of neural stem cells by controlling the necessary checkpoints,which can lead to tumorigenesis and prove to be a curse instead of a blessing or hope.

Effects of Oestrogen on Ischemia-induced Neurogenesis in the Dentate Gyrus of Rats

To study the effects of oestrogcn on ischemia-induced neurogenesis in the hippocampal dentate gyms, thirty-two adult male rats were randomly divided into four groups： the control surgery group with eestrogen administration （SE）, the control surgery group with normal saline administration （SN）, the middle cerebral artery occlusion （MCAO） group with oestrogen administration （ME） and the MCAO group with normal saline administration （MN）. The MCAO rats were occluded for 90 rain by an intraluminal filament and then recirculated. After 1, 3, 12, 24 and 28 h of MCAO, the rats of the four groups were killed to investigate the infarct volume, apoptosis and neurogenesis. The cerebral infarct volume in the ME group was significantly smaller than that of the MN group （P 〈 0.05）. No significant cell loss was seen in the dentate gyms. Cerebral ischemia led to increased neurogenosis, which is independent of cell death in the ipsilateral dentate gyrus（P 〈 0.05）. BrdU-pesitive cells in the ipsilateral dentate gyms of the ME group were significantly increased when compared with those of the MN group（P 〈 0.05）. In the SE group, BrdU-positive cells in both the ipsilateral and contralateral dentate gyms, were increased when compared with those of the SN group （ P 〈 0.05 ）. We concluded that ocstregen plays an important role in neurogenesis, which is independent of ischemia-induced by MCAO in the hippocampal dentate gyms of rats.

Ethanol changes Nestin-promoter induced neural stem cells to disturb newborn dendritic spine remodeling in the hippocampus of mice

Adolescent binge drinking leads to long-lasting disorders of the adult central nervous system,particularly aberrant hippocampal neurogenesis.In this study,we applied in vivo fluorescent tracing using NestinCreERT2::Rosa26-tdTomato mice and analyzed the endogenous neurogenesis lineage progression of neural stem cells(NSCs)and dendritic spine formation of newborn neurons in the subgranular zone of the dentate gyrus.We found abnormal orientation of tamoxifen-induced tdTomato+(tdTom^(+))NSCs in adult mice 2 months after treatment with EtOH(5.0 g/kg,i.p.)for 7 consecutive days.EtOH markedly inhibited tdTom^(+)NSCs activation and hippocampal neurogenesis in mouse dentate gyrus from adolescence to adulthood.EtOH(100 mM)also significantly inhibited the proliferation to 39.2%and differentiation of primary NSCs in vitro.Adult mice exposed to EtOH also exhibited marked inhibitions in dendritic spine growth and newborn neuron maturation in the dentate gyrus,which was partially reversed by voluntary running or inhibition of the mammalian target of rapamycinenhancer of zeste homolog 2 pathway.In vivo tracing revealed that EtOH induced abnormal orientation of tdTom+NSCs and spatial misposition defects of newborn neurons,thus causing the disturbance of hippocampal neurogenesis and dendritic spine remodeling in mice.

Repetitive traumatic brain injury–induced complement C1–related inflammation impairs long-term hippocampal neurogenesis

Repetitive traumatic brain injury impacts adult neurogenesis in the hippocampal dentate gyrus,leading to long-term cognitive impairment.However,the mechanism underlying this neurogenesis impairment remains unknown.In this study,we established a male mouse model of repetitive traumatic brain injury and performed long-term evaluation of neurogenesis of the hippocampal dentate gyrus after repetitive traumatic brain injury.Our results showed that repetitive traumatic brain injury inhibited neural stem cell proliferation and development,delayed neuronal maturation,and reduced the complexity of neuronal dendrites and spines.Mice with repetitive traumatic brain injuryalso showed deficits in spatial memory retrieval.Moreover,following repetitive traumatic brain injury,neuroinflammation was enhanced in the neurogenesis microenvironment where C1q levels were increased,C1q binding protein levels were decreased,and canonical Wnt/β-catenin signaling was downregulated.An inhibitor of C1 reversed the long-term impairment of neurogenesis induced by repetitive traumatic brain injury and improved neurological function.These findings suggest that repetitive traumatic brain injury–induced C1-related inflammation impairs long-term neurogenesis in the dentate gyrus and contributes to spatial memory retrieval dysfunction.

A core scientific problem in the treatment of central nervous system diseases:newborn neurons

It has long been asserted that failure to recover from central nervous system diseases is due to the system's intricate structure and the regenerative incapacity of adult neurons.Yet over recent decades,numerous studies have established that endogenous neurogenesis occurs in the adult central nervous system,including humans'.This has challenged the long-held scientific consensus that the number of adult neurons remains constant,and that new central nervous system neurons cannot be created or renewed.Herein,we present a comprehensive overview of the alterations and regulatory mechanisms of endogenous neurogenesis following central nervous system injury,and describe novel treatment strategies that to rget endogenous neurogenesis and newborn neurons in the treatment of central nervous system injury.Central nervous system injury frequently results in alterations of endogenous neurogenesis,encompassing the activation,proliferation,ectopic migration,diffe rentiation,and functional integration of endogenous neural stem cells.Because of the unfavorable local microenvironment,most activated neural stem cells diffe rentiate into glial cells rather than neurons.Consequently,the injury-induced endogenous neurogenesis response is inadequate for repairing impaired neural function.Scientists have attempted to enhance endogenous neurogenesis using various strategies,including using neurotrophic factors,bioactive materials,and cell reprogramming techniques.Used alone or in combination,these therapeutic strategies can promote targeted migration of neural stem cells to an injured area,ensure their survival and diffe rentiation into mature functional neurons,and facilitate their integration into the neural circuit.Thus can integration re plenish lost neurons after central nervous system injury,by improving the local microenvironment.By regulating each phase of endogenous neurogenesis,endogenous neural stem cells can be harnessed to promote effective regeneration of newborn neurons.This offers a novel approach for treating central nervous system injury.

Tooth loss inhibits neurogenesis in the dentate gyrus of adult mice

Tooth loss has been shown to affect learning and memory in mice and increases the risk of Alz- heimer＇s disease. The dentate gyrus is strongly associated with cognitive function. This study hypothesized that tooth loss affects neurons in the dentate gyrus. Adult male mice were randomly assigned to either the tooth loss group or normal control group. In the tooth loss group, the left maxillary and mandibular molars were extracted. Normal control mice did not receive any intervention. Immunofluorescence staining revealed that the density and absorbance of double- cortinand neuronal nuclear antigen-positive cells were lower in the tooth loss group than in the normal control group. These data suggest that tooth loss may inhibit neurogenesis in the dentate gyrus of adult mice.

A comparison of the spontaneous firing patterns between principal cells and fast spiking interneurons from dentate gyrus in waking guinea pigs

Objective To explore the possible mechanisms that cause the dentate gyrus （DG） neurons to play different roles in information coding. Methods In vivo extracellular single unit recording was performed on 22 waking female guinea pigs, which were positioned in a sound-attenuated recording chamber without any muscular relaxants. The spontaneous firing patterns of the DG neurons were detected and compared. Results There were two different electrophysiologi- cal populations in the DG of guinea pigs, principal cells （PCs） and fast spiking interneurons （INs）. Of the PCs, 1.3% discharged regularly, 48.1% irregularly and 50.6% in bursts ; in contrast, of the INs units, 64.1% discharged regularly, 2.6% irregularly and 33.3% in bursts. The spontaneous firing patterns of PCs were significantly different from those of INs （P 〈0.01 ）. In addition, the differences of several interspike interval （ISI） parameters also have been observed： （1） the ISI coefficients of variation of PCs （3.39 ± 3.56） were significantly higher than those of INs （1.08 ± 0.46） （P 〈0.01） ; （2） the ISI asymmetric indexes of PCs （0. 047±0. 059） were significantly lower than those of INs （0.569±0. 238） （P 〈 0.01 ）. Conclusion In the DG, the spontaneous firing patterns of PCs were significantly different from those of INs. The former were prone to fire in bursts, the latter were prone to fire regularly. The different roles in information coding between PCs and INs might be caused by their different firing patterns.

The effect of Jujuboside A on the evoked field potentials of Granule cells in dentate gyrus

Jujuboside A (JuA) is a main component of Jujubogenin extracted from the seeds of Ziziphus. The authors have not seen any report on JuA's direct effect on the neurons of the central nervous system. This study aimed to assess the effect of JuA on paired pulse responses of dentate gyrus granule cells in urethane anaesthetized rats, used intracerebroventricular (i.c.v.) JuA to mimic in vitro bath conditions in vivo. Paired pulse stimuli with 80ms interpulse interval were used to stimulate the perforant pathway. Evoked responses were recorded in the dentate gyrus cell layer after i.c.v. administration of 0.9% normal saline or JuA. In the first responses, the slopes of excitatory postsynaptic potential (EPSP1) and the amplitudes of population spike (PS1) decreased significantly after administration of JuA while the PS1 latencies increased significantly. In the second responses, the EPSP2 slopes and PS2 latencies were changed similarly to those of the first ones, but PS2 amplitudes increased. The results showed that JuA may have some inhibitory effect on the granule cell excitability mediated by presynaptic mechanism but may have little effect on the excitability mediated by postsynaptic mechanism since the second evoked N methyl D aspartic mediating paired pulse facilitation is a postsynaptic mechanism.

Estimation of the density of neural,glial,and endothelial lineage cells in the adult mouse dentate gyrus

The dentate gyrus subregion of the mammalian hippocampus is an adult neural stem cell niche and site of lifelong neurogenesis.Hypotheses regarding the role of adult-born neuron synaptic integration in hippocampal circuit function are framed by robust estimations of adultborn versus pre/perinatally-born neuron number.In contrast,the non-neurogenic functions of adult neural stem cells and their immediate progeny,such as secretion of bioactive growth factors and expression of extracellular matrix-modifying proteins,lack similar framing due to few estimates of their number versus other prominent secretory cells.Here,we apply immunohistochemical methods to estimate cell density of neural stem/progenitor cells versus other major classes of glial and endothelial cell types that are potentially secretory in the dentate gyrus of adult mice.Of the cell types quantified,we found that GFAP^(+)SOX2^(+)stellate astrocytes were the most numerous,followed by CD31^(+)endothelia,GFAP-SOX2^(+)intermediate progenitors,Olig2^(+)oligodendrocytes,Iba1+microglia,and GFAP^(+)SOX2^(+)radial glia-like neural stem cells.We did not observe any significant sex differences in density of any cell population.Notably,neural stem/progenitor cells were present at a similar density as several cell types known to have potent functional roles via their secretome.These findings may be useful for refining hypotheses regarding the contributions of these cell types to regulating hippocampal function and their potential therapeutic uses.All experimental protocols were approved by the Ohio State University Institutional Animal Care and Use Committee(protocol#2016A00000068)on July 14,2016.

Bumetanide promotes neural precursor cell regeneration and dendritic development in the hippocampal dentate gyrus in the chronic stage of cerebral ischemia

Bumetanide has been shown to lessen cerebral edema and reduce the infarct area in the acute stage of cerebral ischemia. Few studies focus on the effects of bumetanide on neuroprotection and neurogenesis in the chronic stage of cerebral ischemia. We established a rat model of cerebral ischemia by injecting endothelin-1 in the left cortical motor area and left corpus striatum. Seven days later, bumetanide 200 μg/kg/day was injected into the lateral ventricle for 21 consecutive days with a mini-osmotic pump. Results demonstrated that the number of neuroblasts cells and the total length of dendrites increased, escape latency reduced, and the number of platform crossings increased in the rat hippocampal dentate gyrus in the chronic stage of cerebral ischemia. These findings suggest that bumetanide promoted neural precursor cell regeneration, dendritic development and the recovery of cognitive function, and protected brain tissue in the chronic stage of ischemia.

Cognitive impairment after traumatic brain injury is associated with reduced long-term depression of excitatory postsynaptic potential in the rat hippocampal dentate gyrus

Traumatic brain injury can cause loss of neuronal tissue, remote symptomatic epilepsy, and cognitive deficits. However, the mechanisms underlying the effects of traumatic brain injury are not yet clear. Hippocampal excitability is strongly correlated with cognitive dysfunction and remote symptomatic epilepsy. In this study, we examined the relationship between traumatic brain injury-induced neuronal loss and subsequent hippocampal regional excitability. We used hydraulic percussion to generate a rat model of traumatic brain injury. At 7 days after injury, the mean modified neurological severity score was 9.5, suggesting that the neurological function of the rats was remarkably impaired. Electrophysiology and immunocytochemical staining revealed increases in the slope of excitatory postsynaptic potentials and long-term depression（indicating weakened long-term inhibition）, and the numbers of cholecystokinin and parvalbumin immunoreactive cells were clearly reduced in the rat hippocampal dentate gyrus. These results indicate that interneuronal loss and changes in excitability occurred in the hippocampal dentate gyrus. Thus, traumatic brain injury-induced loss of interneurons appears to be associated with reduced long-term depression in the hippocampal dentate gyrus.

Effects of butternut squash extract on dentate gyrus cell proliferation and spatial learning in male adult rats

Previous studies reported that some plants, including butternut squash, exert positive effects on the brain. However, few studies have examined the effects of butternut squash on learning, memory, and neurogenesis. This study studied the effects of butternut squash extract on spatial learning and cell proliferation in the dentate gyrus of healthy male rats. Thirty-five male Wistar rats were intraperitoneally injected with 0, 50, 100, 200 and 400 mg/kg butternut squash extract once daily for 2 months. After the last administration, rat＇s spatial memory was studied using the Morris water maze. Finally, rats were sacrificed and hippocampal sections were prepared for light microscopy and bromodeoxyuridine immunohistochemistry studies. The results revealed that escape latency and swim distance decreased in all treatment groups compared with the control rats, and that the number of bromodeoxyuridine-positive cells in the dentate gyrus was significantly increased in the treatment groups compared with the controls. These findings suggest that butternut squash extract improves the learning and memory abilities of male rats, and increases the proliferation of dentate gyrus cells.

Long-term administration of scopolamine interferes with nerve cell proliferation, differentiation and migration in adult mouse hippocampal dentate gyrus, but it does not induce cell death

Long-term administration of scopolamine, a muscarinic receptor antagonist, can inhibit the survival of newly generated cells, but its effect on the proliferation, differentiation and migration of nerve cells in the adult mouse hippocampal dentate gyrus remain poorly understood. In this study, we used immunohistochemistry and western blot methods to weekly detect the biological behaviors of nerve cells in the hippocampal dentate gyrus of adult mice that received intraperito- neal administration of scopolamine for 4 weeks. Expression of neuronal nuclear antigen （NeuN; a neuronal marker） and Fluoro-]ade B （a marker for the localization of neuronal degeneration） was also detected. After scopolamine treatment, mouse hippocampal neurons did not die, and Ki-67 （a marker for proliferating cells）-immunoreactive cells were reduced in number and reac hed the lowest level at 4 weeks. Doublecortin （DCX; a marker for newly generated neurons）-im- munoreactive cells were gradually shortened in length and reduced in number with time. After scopolamine treatment for 4 weeks, nearly all of the 5-bromo-2＇-deoxyuridine （BrdU）-labeled newly generated cells were located in the subgranular zone of the dentate gyrus, but they did not migrate into the granule cell layer. Few mature BrdU/NeuN double-labeled cells were seen in the subgranular zone of the dentate gyrus. These findings suggest that long-term administration of scopolamine interferes with the proliferation, differentiation and migration of nerve cells in the adult mouse hippocampal dentate gyrus, but it does not induce cell death.

Apoptosis and autophagy control cell proliferation in the dentate gyrus following hippocampal lesion

Brain injuries often result in the promotion of cell proliferation in the hippocampal dentate gyrus（DG）,but the number of newborn cells declines with time.However,the cause of this decline remains poorly understood.Elucidation of the fate of these newborn cells will further the understanding of the pathological process and treatment of brain injury.In the present study,the number of newborn cells was quantitatively analyzed using an unbiased stereological method following hippocampal lesion by kainic acid,in combination with detection of apoptosis and autophagy.Results revealed that hippocampal lesion resulted in a significantly increased number of 5-bromo-2-deoxyuridine（BrdU）-positive cells in the DG,which subsequently decreased with time.BrdU/cleaved caspase-3 double-labeled cells were detected in the granular cell layer and hilus of DG.However,expressions of LC3-11,Beclin 1,and p53 were upregulated,and pro-caspase-3 and Bcl-2 were downregulated.Results indicated that hippocampal lesion in adult rats resulted in significant cell proliferation in the DG,which subsequently reduced with time.In addition,results suggested that apoptosis and autophagic processes could regulate cell proliferation in the DG following hippocampal lesion.

Neurons in the hippocampal CA1 region,but not the dentate gyrus,are susceptible to oxidative stress in rats with streptozotocin-induced type 1 diabetes

In this study, we investigated the effects of streptozotocin-induced type 1 diabetes on antioxi- dant-like protein-1 immunoreactivity, protein carbonyl levels, and malondialdehyde formation, a marker for lipid peroxidation, in the hippocampus. For this study, streptozotocin （75 mg/kg） was intraperitoneally injected into adult rats to induce type 1 diabetes. The three experimental pa- rameters were determined at 2, 3, 4 weeks after streptozotocin treatment. Fasting blood glucose levels significantly increased by 20.7-21.9 mM after streptozotocin treatment. The number of antioxidant-like protein-1 immunoreactive neurons significantly decreased in the hippocampal CA1 region, but not the dentate gyrus, 3 weeks after streptozotocin treatment compared to the control group. Malondialdehyde and protein carbonyl levels, which are modified by oxidative stress, significantly increased with a peak at 3 weeks after malondialdehyde treatment, and then decreased 4 weeks after malondialdehyde treatment. These results suggest that neurons in the hippocampal CA1 region, but not the dentate gyrus, are susceptible to oxidative stress 3 weeks after malondialdehyde treatment.

Status epilepticus increases mature granule cells in the molecular layer of the dentate gyrus in rats

Enhanced neurogenesis in the dentate gyrus of the hippocampus following seizure activity, especially status epilepticus, is associated with ectopic residence and aberrant integration of newborn granule cells. Hilar ectopic granule cells may be detrimental to the stability of dentate circuitry by means of their electrophysiological properties and synaptic connectivity. We hypothesized that status epilepticus also increases ectopic granule cells in the molecular layer. Status epilepticus was induced in male Sprague-Dawley rats by intraperitoneal injection of pilocarpine. Immunostaining showed that many doublecortin-positive cells were present in the molecular layer and the hilus 7 days after the induction of status epilepticus. At least 10 weeks after status epilepticus, the estimated number of cells positive for both prospero homeobox protein 1 and neuron-specific nuclear protein in the hilus was significantly increased. A similar trend was also found in the molecular layer. These findings indicate that status epilepticus can increase the numbers of mature and ectopic newborn granule cells in the molecular layer.

Role of hippocampal dentate gyrus neurons in the protective effects of heat shock factor 1 on working memory

Increasing evidence suggests that heat shock factor 1 exerts endogenous protective effects on working memory under conditions of chronic psychological stress. However, the precise underlying mechanisms remain poorly understood. This study examined the protective factors affecting working memory in heat shock transcription factor 1 gene knockout mice. The results indicated that the number of correct T maze alternations decreased following mild chronic psychological stress in knockout mice. This change was accompanied by a decrease in neurogenesis and an increase in neuronal apoptosis in the hippocampal dentate gyrus. The number of correct T maze alternations was positively correlated with neurogenesis in hippocampal dentate gyrus, and negatively correlated with neuronal apoptosis. In wild type mice, no significant difference was detected in the number of correct T maze alternations or neuronal apoptosis in hippocampal dentate gyrus. These results indicate that the heat shock factor 1 gene has an endogenous protective role in working memory during mild chronic psychological stress associated with dentate gyrus neuronal apoptosis Moreover, dentate gyrus neurogenesis appears to participate in the protective mechanism.

Effects of bone morphogenetic protein-4 on spatial memory and cholinergic expression in the dentate gyrus after fornix-fimbria transection in rats

BACKGROUND： Previous experiments have confirmed bone morphogenetic proteins （BMPs） upregulate cholinergic expression in neurons isolated from the embryonic rat hippocampus and cerebral cortex. Therefore, BMPs could be useful for treating Alzheimer＇s disease and other neurodegenerative diseases. OBJECTIVE： BMP-4 was infused into the hippocampal dentate gyrus of fomix-fimbria transected rats to test the effects of BMP-4 on cholinergic expression in dentate gyrus neurons, and to observe changes in spatial memory behavior. DESIGN： A randomized controlled animal experiment. SETTING： Department of Neurosurgery and Laboratory for Cell Biology, Institute of Geriatrics, General Hospital of Chinese PLA. MATERIALS： Twenty-seven healthy adult male Sprague Dawley （SD） rats, weighing 250-300 g, were provided by the Laboratory Animal Center of the General Hospital of Chinese PLA. Reagents： BMP-4 （B-2680, Sigma Company） and choline acetyl transferase （CHAT） antibody （AB5042, Chemicon Company） were used in this study. Equipments： a rat stereotaxic instrument （type： SN-2N, Narushige Group, Japan） and Image-prog-plus image analysis software （Media Cybernetics company, USA） were used in this study. The protocol was carried out in accordance with ethical guidelines for the use and care of animals. METHODS： This experiment was performed in the Institute of Geriatrics, General Hospital of Chinese PLA between July 2004 and March 2005. Rats were randomly divided into 4 groups： Alzheimer＇s disease group （n = 7）, normal control group （n = 5）, BMP-4-Alzheimer＇s disease group （n = 8）, and model group （n = 7）. In the Alzheimer＇s disease group, the left hippocampal fomix-fimbria of rats was transected to mimic Alzheimer＇s disease symptoms. In the BMP-4-Alzheimer＇s disease group, 1 μt L BMP-4 （10 mg/L） was perfused into the left dentate gyrus with a microinjector at 1 μ L/min. In the model group, 1 μ L saline was perfused into the same position by the same method. Twenty-eight days after injection, Morris water maze test was performed in all rats to test spatial memory. Time-to-platform and swim-path length were recorded. Immunohistochemical staining of cholinergic neurons was performed on brain sections containing dentate gyrus. The area covered by ChAT-positive cells was analyzed using an Image-prog-plus image analysis software. MAIN OUTCOME MEASURES： Area covered by ChAT-positive cells in the dentate gyrus. Time-to-platform and swim path-length. RESULTS： Twenty-seven rats were included in the final analysis. In the Alzheimer＇s disease group, the area covered by ChAT-positive cells was significantly smaller compared with the normal control group （F = 76.03, P 〈 0.01）. The area covered by ChAT-positive cells was significantly larger in the BMP-4- Alzheimer＇s disease group than in the model group （F = 35.17, P 〈 0.05）, but significantly smaller than in the normal control group （F = 40.17, P 〈 0.05）. Time-to-platform and swim-path length were significantly longer in the Alzheimer＇s disease group than in the normal control group （F =24.62 and 631.58, respectively, both P 〈 0.05）. Time-to-platform and swim-path length were significantly shorter in the BMP4-Alzheimer＇s disease group compared with the model group （F= 22.06 and 606.89, respectively P 〈 0.05）. CONCLUSION： Injection of BMP-4 into the dentate gyrus of Alzheimer＇s disease model rats alleviates central cholinergic system injury and concomitantly improves spatial memory.