Degeneration of newly formed CA1 neurons following global ischemia in the rat

Loose patch clamp membrane current measurements in cornus ammonis 1 neurons in murine hippocampal slices

Hippocampal pyramidal neuronal activity has been previously studied using conventional patch clamp in isolated cells and brain slices. We here introduce the loose patch clamping study of voltage-activated currents from in situ pyramidal neurons in murine cornus ammonis 1 hippocampal coronal slices. Depolarizing pulses of 15-ms duration elicited early transient inward, followed by transient and prolonged outward currents in the readily identifiable junctional region between the stratum pyramidalis (SP) and oriens (SO) containing pyramidal cell somas and initial segments. These resembled pyramidal cell currents previously recorded using conventional patch clamp. Shortening the depolarizing pulses to >1-2 ms continued to evoke transient currents; hyperpolarizing pulses to varying voltages evoked decays whose time constants could be shortened to <1 ms, clarifying the speed of clamping in this experimental system. The inward and outward currents had distinct pharmacological characteristics and voltage-dependent inactivation and recovery from inactivation. Comparative recordings from the SP, known to contain pyramidal cell somas, demonstrated similar current properties. Recordings from the SO and stratum radiatum demonstrated smaller inward and outward current magnitudes and reduced transient outward currents, consistent with previous conventional patch clamp results from their different interneuron types. The loose patch clamp method is thus useful for in situ studies of neurons in hippocampal brain slices.

Connectome-based prediction of functional impairment in experimental stroke models

Experimental rat models of stroke and hemorrhage are important tools to investigate cerebrovascular disease pathophysiology mechanisms, yet how significant patterns of functional impairment induced in various models of stroke are related to changes in connectivity at the level of neuronal populations and mesoscopic parcellations of rat brains remain unresolved. To address this gap in knowledge, we employed two middle cerebral artery occlusion models and one intracerebral hemorrhage model with variant extent and location of neuronal dysfunction. Motor and spatial memory function was assessed and the level of hippocampal activation via Fos immunohistochemistry. Contribution of connectivity change to functional impairment was analyzed for connection similarities, graph distances and spatial distances as well as the importance of regions in terms of network architecture based on the neuroVIISAS rat connectome. We found that functional impairment correlated with not only the extent but also the locations of the injury among the models. In addition, via coactivation analysis in dynamic rat brain models, we found that lesioned regions led to stronger coactivations with motor function and spatial learning regions than with other unaffected regions of the connectome. Dynamic modeling with the weighted bilateral connectome detected changes in signal propagation in the remote hippocampus in all 3 stroke types, predicting the extent of hippocampal hypoactivation and impairment in spatial learning and memory function. Our study provides a comprehensive analytical framework in predictive identification of remote regions not directly altered by stroke events and their functional implication.

Osteopontin mediates the formation of corpora amylacea-like structures from degenerating neurons in the CA1 region of the rat hippocampus after ischemia

We previously demonstrated that osteopontin (OPN) is closely associated with calcium precipitation in response to ischemic brain insults. The present study was designed to elucidate the possible association between deposition of OPN and progressive neurodegeneration in the ischemic hippocampus. To address this, we analyzed the OPN deposits in the rat hippocampus after global cerebral ischemia in the chronic phase (4 to 12 weeks) after reperfusion using immunoelectron microscopy and correlative light and electron microscopy. We identified three different types of OPN deposits based on their morphological characteristics, numbered according to the order in which they evolved. Dark degenerative cells that retained cellular morphology were frequently observed in the pyramidal cell layer, and type I OPN deposits were degenerative mitochondria that accumulated among these cells. Type II deposits evolved into more complex amorphous structures with prominent OPN deposits within their periphery and within degenerative mitochondria-like structures. Finally, type III had large concentric laminated structures with irregularly shaped bodies in the center of the deposits. In all types, OPN expression was closely correlated with calcification, as confirmed by calcium fixation and Alizarin Red staining. Notably, type II and III deposits were highly reminiscent of corpora amylacea, glycoprotein-rich aggregates found in aged brains, or neurodegenerative disease, which was further confirmed by ubiquitin expression and periodic acid-Schiff staining. Overall, our data provide a novel link between ongoing neurodegeneration and the formation of corpora amylacea-like structures and calcium deposits in the ischemic hippocampus, suggesting that OPN may play an important role in such processes.

Global Cerebral Ischemia in Male Long Evans Rats Impairs Dopaminergic/ΔFosB Signalling in the Mesocorticolimbic Pathway Without Altering Delay Discounting Rates

Global cerebral ischemia (GCI) in rats has been shown to promote exploration of anxiogenic zones of the Elevated-Plus Maze (EPM) and Open Field Test (OFT). This study investigated changes in impulsive choice and/or defensive responses as possible contributors of heightened anxiogenic exploration observed after ischemia. Impulsivity was assessed using delay discounting (DD) paradigms, while the Predator Odour Test (PO) served to assess changes in defensive responses towards a naturally aversive stimulus. Male Long Evans rats underwent 9 days of autoshaping training and 24 days of DD training prior to GCI or sham surgery (n = 9/group). Post-surgery, rats completed the OFT, EPM, and PO, followed by 6 days of DD sessions. Blood droplets served to evaluate corticosterone secretion associated with PO exposure. With impulsivity being regulated through mesocorticolimbic monoaminergic pathways, we also characterised post-ischemic changes in the expression of dopamine D₂ receptors (DRD₂), dopamine transporters (DAT), and 1FosB in the basolateral amygdala (BLA), nucleus accumbens core (NAcC) and shell (NAcS), and ventromedial prefrontal cortex (vmPFC) using immunohistofluorescence. Our findings revealed no impact of GCI on delay discounting rates, while PO approach behaviours were minimally affected. Nonetheless, GCI significantly reduced DRD₂ and ΔFosB-ir in the NAcS and NAcC, respectively, while DAT-ir was diminished in both NAc subregions. Collectively, our findings refine the understanding of cognitive-behavioural and biochemical responses following stroke or cardiac arrest. They support significant alterations to the dopaminergic mesocorticolimbic pathway after ischemia, which are not associated with altered impulsive choice in a DD task but may influence locomotor exploration of the OFT and EPM.

CA1 Hippocampal Pyramidal Cells in Rats, Resuscitated From 8 Minutes of Ventricular Fibrillation Cardiac Arrest, Recover After 20 Weeks of Survival: A Retrospective Pilot Study

PURPOSE

The cornu ammonis 1 (CA1) region of the hippocampus is specifically vulnerable to global ischemia. We hypothesized that histopathological outcome in a ventricular fibrillation cardiac arrest (VFCA) rat model depends on the time point of the examination.

METHODS

Male Sprague-Dawley rats were put into VFCA for 8 min, received chest compressions for 2 min, and were defibrillated to achieve return of spontaneous circulation. Animals surviving for 80 min, 14 days and 140 days were compared with controls. Viable neurons were counted in a 500 μm sector of the CA1 region and layer thickness measured. Microglia cells and astrocytes were counted in a 250×300 μm aspect.

RESULTS

Control and 80 min surviving animals had similar numbers of pyramidal neurons in the CA1 region. In 14 days and 140 days survivors neuron numbers and layer thickness were severely diminished compared with controls (P < 0.001). Two-thirds of the 140 days survivors showed significantly more viable neurons than the last third. Microglia was increased in 14 days survivors compared with controls and 140 days survivors, while astrocytes increased in 14 days and 140 days survivors compared with controls (P < 0.001). 140 days survivors had significantly higher astrocyte counts compared with 14 days survivors.

CONCLUSIONS

The amount and type of brain lesions present after global ischemia depend on the survival time. A consistent reduction in pyramidal cells in the CA1 region was present in all animals 14 days after VFCA, but in two-thirds of animals a repopulation of pyramidal cells seems to have taken place after 140 days.

Global cerebral ischemia in adolescent male Long Evans rats: Effects of vanillic acid supplementation on stress response, emotionality, and visuospatial memory

The developmental period is critical in delineating plastic response to internal and external events. However, neurobehavioural effects of global cerebral ischemia (GCI) in the maturing brain remain largely unknown. This study characterised the effects of GCI experienced at puberty on adulthood (1) hippocampus CA1 neuronal damage, (2) cognitive and emotional impairments, and (3) glucocorticoid receptor (GR) expression. Effects of adolescent exposure to the phenol vanillic acid (VA) on post-ischemic outcomes were also determined. Male Long Evans rats (n = 35) were supplemented for 21 consecutive days (postnatal days 33-53) with VA (91 mg/kg) or nut paste vehicle (control) prior to a 10-min GCI or sham surgery. As adults, rats were tested in the Open Field Test (OFT), Elevated-Plus Maze (EPM), and Barnes Maze (BM). GR expression was determined in the basolateral amygdala (BLA), CA1, and paraventricular nucleus (PVN), and brain injury assessed via CA1 neuronal density. Adolescent GCI exposure induced extensive hippocampal CA1 injury, which was not prevented by VA supplementation. Behaviourally, GCI increased EPM exploration while having no impact on spatial memory. VA intake increased OFT peripheral exploration. Notably, while no delayed changes in CA1 and PVN GR immunoreactivity were noted, both treatments separately increased BLA GR expression when compared with sham-nut paste rats. Age at GCI occurrence plays a critical role on post-ischemic impairments. The observation of minimal functional impairments despite important CA1 neuronal damage supports use of compensatory mechanisms. Our findings also show daily VA supplementation during adolescence to have no protective effects on post-ischemic outcomes, contrasting adult intake.

Alzheimer's Disease and Empathic Abilities: The Proposed Role of the Cingulate Cortex

In recent years there has been increasing interest in examining the role of empathic abilities in Alzheimer’s disease (AD). Empathy, the ability to understand and share another person’s feelings, implies the existence of emotional and cognitive processes and is a pivotal aspect for success in social interactions. In turn, self-empathy is oriented to one’s thoughts and feelings. Decline of empathy and self-empathy can occur during the AD continuum and can be linked to different neuroanatomical pathways in which the cingulate cortex may play a crucial role. Here, we will summarize the involvement of empathic abilities through the AD continuum and further discuss the potential neurocognitive mechanisms that contribute to decline of empathy and self-empathy in AD.

Attenuating effect of paroxetine on memory impairment following cerebral ischemia-reperfusion injury in rat: The involvement of BDNF and antioxidant capacity

Memory impairments are frequently reported in patients suffering from brain ischemic diseases. Oxidative/nitrosative stress, synaptic plasticity, and brain-derived neurotrophic factor (BDNF) are involved in the physiopathology of brain ischemia-induced memory disorders. In the present study, the effect of paroxetine as an efficacious antidepressant medication with antioxidant properties was evaluated on passive avoidance memory deficit following cerebral ischemia in rats. Transient occlusion of common carotid arteries was applied to induce ischemia-reperfusion injury in male Wistar rats. Paroxetine (5, 10, 20 mg/kg) was administered intraperitoneally once daily before (for 3 days) or after (for 7 days) the induction of ischemia. A week after ischemia-reperfusion injury, passive avoidance memory, long-term potentiation (LTP), BDNF levels, total antioxidant capacity, the activity of antioxidant enzymes (including catalase, glutathione peroxidase, and superoxide dismutase), the concentration of malondialdehyde (MDA), and nitric oxide (NO) were investigated in the hippocampus. In the passive avoidance test, paroxetine significantly increased the step-through latency and decreased the time spent in the dark compartment. This affirmative function of paroxetine on the passive avoidance memory was accompanied by the improvement of hippocampal LTP and an obvious augmentation in the BDNF contents. Besides, paroxetine caused a significant rise in the total antioxidant capacity and antioxidant enzyme activity; while decreased the hippocampal levels of NO and MDA. It was ultimately attained that paroxetine attenuates cerebral ischemia-induced passive avoidance memory dysfunction in rats by the enhancement of hippocampal synaptic plasticity and BDNF content together with the suppression of oxidative/nitrosative stress.

Motor Cortex and Hippocampus Display Decreased Heme Oxygenase Activity 2 Weeks After Ventricular Fibrillation Cardiac Arrest in Rats

Heme oxygenase (HO) and biliverdin reductase (BVR) activities are important for neuronal function and redox homeostasis. Resuscitation from cardiac arrest (CA) frequently results in neuronal injury and delayed neurodegeneration that typically affect vulnerable brain regions, primarily hippocampus (Hc) and motor cortex (mC), but occasionally also striatum and cerebellum. We questioned whether these delayed effects are associated with changes of the HO/BVR system. We therefore analyzed the activities of HO and BVR in the brain regions Hc, mC, striatum and cerebellum of rats subjected to ventricular fibrillation CA (6 min or 8 min) after 2 weeks following resuscitation, or sham operation. From all investigated regions, only Hc and mC showed significantly decreased HO activities, while BVR activity was not affected. In order to find an explanation for the changed HO activity, we analyzed protein abundance and mRNA expression levels of HO-1, the inducible, and HO-2, the constitutively expressed isoform, in the affected regions. In both regions we found a tendency for a decreased immunoreactivity of HO-2 using immunoblots and immunohistochemistry. Additionally, we investigated the histological appearance and the expression of markers indicative for activation of microglia [tumor necrosis factor receptor type I (TNFR1) mRNA and immunoreactivity for ionized calcium-binding adapter molecule 1 (Iba1])], and activation of astrocytes [immunoreactivity for glial fibrillary acidic protein (GFAP)] in Hc and mC. Morphological changes were detected only in Hc displaying loss of neurons in the cornu ammonis 1 (CA1) region, which was most pronounced in the 8 min CA group. In this region also markers indicating inflammation and activation of pro-death pathways (expression of HO-1 and TNFR1 mRNA, as well as Iba1 and GFAP immunoreactivity) were upregulated. Since HO products are relevant for maintaining neuronal function, our data suggest that neurodegenerative processes following CA may be associated with a decreased capacity to convert heme into HO products in particularly vulnerable brain regions.

Roles of GABAA receptor α5 subunit on locomotion and working memory in transient forebrain ischemia in mice

The γ-aminobutyric acid A (GABA_A) receptor, which contains a chloride channel, is a typical inhibitory neurotransmitter receptor in the central nervous system. Although the GABAergic neurotransmitter system has been discovered to be involved in various psychological behaviors, such as anxiety, convulsions, and cognitive function, its functional changes under conditions of ischemic pathological situation are still uncovered. In the present study, we attempted to elucidate the functional changes in the GABAergic system after transient forebrain ischemia in mice. A bilateral common carotid artery occlusion for 20 min was used to establish a model of transient forebrain ischemia/reperfusion (tI/R). Delayed treatment with diazepam, a positive allosteric modulator of the GABA_A receptor, increased locomotor activity in the open field test and spontaneous alternations in the Y-maze test in tI/R mice, but not in shams. Delayed treatment with diazepam did not alter neuronal death or the number of GABAergic neurons in tI/R mice. However, tI/R induced changes in the protein levels of GABA_A receptor subunits in the hippocampus. In particular, the most marked increase in the tI/R group was found in the level of α5 subunit of the GABA_A receptor. Similar to delayed treatment with diazepam, delayed treatment with imidazenil, an α5-sensitive benzodiazepine, increased spontaneous alternations in the Y-maze in tI/R mice, whereas zolpidem, an α5-insensitive benzodiazepine, failed to show such effects. These results suggest that tI/R-induced changes in the level of the α5 subunit of the GABA_A receptor can alter the function of GABAergic drugs in a mouse model of forebrain ischemia.

Prognostic value of magnetic resonance imaging performed during the subacute phase in adult patients with hypoxic-ischemic encephalopathy for long-term neurological outcomes

OBJECTIVE

To investigate the value of a model based on brain magnetic resonance imaging (MRI) performed in the subacute phase (between the 1st and 30th day) in predicting long-term neurological outcomes of adult hypoxic-ischemic encephalopathy (HIE) patients.

METHODS

Ninety-six adult HIE patients who underwent conventional MRI and diffusion-weighted imaging (DWI) during the subacute phase were retrospectively analyzed. Favorable (Cerebral Performance Categories (CPC) 1-2) and unfavorable outcome (CPC 3-5) groups were created based on patient neurological status approximately three months after the onset of hypoxic-ischemic events. A multivariate stepwise regression model was applied after univariate analysis of MRI findings, and then the overall MRI score, Alberta Stroke Program Early Computed Tomography Score (ASPECTS), Bilateral ASPECTS (Bi-ASPECTS), modified ASPECTS (mASPECTS) and Bi-ASPECTS combined with posterior circulation ASPECTS (PC-ASPECTS) were calculated based on MRI findings. Receiver operating characteristic (ROC) curves were used to assess prognostic accuracy.

RESULTS

Both univariate and multivariate analyses showed the cerebral cortex and cerebellum, neostriatum, hippocampus, brainstem and postanoxic leukoencephalopathy were independent prognostic factors for unfavorable outcomes. The multivariate regression analysis resulted in an overall classification accuracy of 84.4%, a sensitivity of 84.2% (95% CI, 71.6-92.1%), and a specificity of 92.3% (95% CI, 78.0-98.0%) for unfavorable outcomes. The model had an areas under the ROC curves (AUC) of 0.944 (95% CI, 0.901-0.987); the MRI overall scores were 0.918 (95% CI, 0.866, 0.971), ASPECTS 0.839 (95% CI, 0.755, 0.923), Bi-ASPECTS 0.837 (95% CI, 0.753, 0.922), mASPECTS 0.851(95% CI, 0.771, 0.931) and Bi-ASPECTS+PC-ASPECTS 0.876 (95% CI, 0.806, 0.946).

CONCLUSIONS

The multivariate model based on conventional MRI combined with DWI performed in the subacute phase could help predict the prognosis of adult HIE with high performance.

Effects of regional body temperature variation during asphyxial cardiac arrest on mortality and brain damage in a rat model

To date, hypothermia has focused on improving rates of resuscitation to increase survival in patients sustaining cardiac arrest (CA). Towards this end, the role of body temperature in neuronal damage or death during CA needs to be determined. However, few studies have investigated the effect of regional temperature variation on survival rate and neurological outcomes. In this study, adult male rats (12 week-old) were used under the following four conditions: (i) whole-body normothermia (37 ± 0.5 °C) plus (+) no asphyxial CA, (ii) whole-body normothermia + CA, (iii) whole-body hypothermia (33 ± 0.5 °C)+CA, (iv) body hypothermia/brain normothermia + CA, and (v) brain hypothermia/body normothermia + CA. The survival rate after resuscitation was significantly elevated in groups exposed to whole-body hypothermia plus CA and body hypothermia/brain normothermia plus CA, but not in groups exposed to whole-body normothermia combined with CA and brain hypothermia/body normothermia plus CA. However, the group exposed to hypothermia/brain normothermia combined with CA exhibited higher neuroprotective effects against asphyxial CA injury, i.e. improved neurological deficit and neuronal death in the hippocampus compared with those involving whole-body normothermia combined with CA. In addition, neurological deficit and neuronal death in the group of rat exposed to brain hypothermia/body normothermia and CA were similar to those in the rats subjected to whole-body normothermia and CA. In brief, only brain hypothermia during CA was not associated with effective survival rate, neurological function or neuronal protection compared with those under body (but not brain) hypothermia during CA. Our present study suggests that regional temperature in patients during CA significantly affects the outcomes associated with survival rate and neurological recovery.

The Phenolic Components of Gastrodia elata improve Prognosis in Rats after Cerebral Ischemia/Reperfusion by Enhancing the Endogenous Antioxidant Mechanisms

Pharmacological or spontaneous thrombolysis in ischemic stroke triggers an outbreak of reactive oxygen species and results in neuron death. Nrf2-mediated antioxidation in cells has been proved as a pivotal target for neuroprotection. This research reports that phenolic components of Gastrodia elata Blume (PCGE), a traditional Chinese medicine, can alleviate the pathological lesions in the penumbra and hippocampus by increasing the survival of neurons and astrocytes and improve neurofunction and cognition after reperfusion in a rat model of middle cerebral artery occlusion. LDH assay indicated that pretreatment of cells with PCGE (25 μg/ml) for 24 h significantly reduced H₂O₂-induced cell death in astrocytes and SH-SY5Y cells. Western blot showed that the nucleus accumulation of Nrf2 and the expression of cellular HO-1 and NQO-1, two of Nrf2 downstream proteins, were increased in both cells. BDNF, an Nrf2-dependent neurotrophic factor, was also upregulated by PCGE in astrocytes. These results illustrated that PCGE can reduce the cerebral ischemia/reperfusion injury and improve prognosis by remedying the cell damage within affected tissues. The protective effects of PCGE seem to be via activation of a Nrf2-mediated cellular defense system. Therefore, PCGE could be a therapeutic candidate for ischemic stroke and other oxidative stress associated neurological disorders.

Targeting CDK5 post-stroke provides long-term neuroprotection and rescues synaptic plasticity

Post-stroke cognitive impairment is a major cause of long-term neurological disability. The prevalence of post-stroke cognitive deficits varies between 20% and 80% depending on brain region, country, and diagnostic criteria. The biochemical mechanisms underlying post-stroke cognitive impairment are not known in detail. Cyclin-dependent kinase 5 is involved in neurodegeneration, and its dysregulation contributes to cognitive disorders and dementia. Here, we administered cyclin-dependent kinase 5-targeting gene therapy to the right hippocampus of ischemic rats after transient right middle cerebral artery occlusion. Cyclin-dependent kinase 5 RNA interference prevented the impairment of reversal learning four months after ischemia as well as neuronal loss, tauopathy, and microglial hyperreactivity. Additionally, cyclin-dependent kinase 5 silencing increased the expression of brain-derived neurotrophic factor in the hippocampus. Furthermore, deficits in hippocampal long-term potentiation produced by excitotoxic stimulation were rescued by pharmacological blockade of cyclin-dependent kinase 5. This recovery was blocked by inhibition of the TRKB receptor. In summary, these findings demonstrate the beneficial impact of cyclin-dependent kinase 5 reduction in preventing long-term post-ischemic neurodegeneration and cognitive impairment as well as the role of brain-derived neurotrophic factor/TRKB in the maintenance of normal synaptic plasticity.

Spatiotemporal Progression of Microcalcification in the Hippocampal CA1 Region following Transient Forebrain Ischemia in Rats: An Ultrastructural Study

Calcification in areas of neuronal degeneration is a common finding in several neuropathological disorders including ischemic insults. Here, we performed a detailed examination of the onset and spatiotemporal profile of calcification in the CA1 region of the hippocampus, where neuronal death has been observed after transient forebrain ischemia. Histopathological examinations showed very little alizarin red staining in the CA1 pyramidal cell layer until day 28 after reperfusion, while prominent alizarin red staining was detected in CA1 dendritic subfields, particularly in the stratum radiatum, by 14 days after reperfusion. Electron microscopy using the osmium/potassium dichromate method and electron probe microanalysis revealed selective calcium deposits within the mitochondria of degenerating dendrites at as early as 7 days after reperfusion, with subsequent complete mineralization occurring throughout the dendrites, which then coalesced to form larger mineral conglomerates with the adjacent calcifying neurites by 14 days after reperfusion. Large calcifying deposits were frequently observed at 28 days after reperfusion, when they were closely associated with or completely engulfed by astrocytes. In contrast, no prominent calcification was observed in the somata of CA1 pyramidal neurons showing the characteristic features of necrotic cell death after ischemia, although what appeared to be calcified mitochondria were noted in some degenerated neurons that became dark and condensed. Thus, our data indicate that intrahippocampal calcification after ischemic insults initially occurs within the mitochondria of degenerating dendrites, which leads to the extensive calcification that is associated with ischemic injuries. These findings suggest that in degenerating neurons, the calcified mitochondria in the dendrites, rather than in the somata, may serve as the nidus for further calcium precipitation in the ischemic hippocampus.

Omega-3 Fatty Acids: Possible Neuroprotective Mechanisms in the Model of Global Ischemia in Rats

Background. Omega-3 (ω3) administration was shown to protect against hypoxic-ischemic injury. The objectives were to study the neuroprotective effects of ω3, in a model of global ischemia. Methods. Male Wistar rats were subjected to carotid occlusion (30 min), followed by reperfusion. The groups were SO, untreated ischemic and ischemic treated rats with ω3 (5 and 10 mg/kg, 7 days). The SO and untreated ischemic animals were orally treated with 1% cremophor and, 1 h after the last administration, they were behaviorally tested and euthanized for neurochemical (DA, DOPAC, and NE determinations), histological (Fluoro jade staining), and immunohistochemical (TNF-alpha, COX-2 and iNOS) evaluations. The data were analyzed by ANOVA and Newman-Keuls as the post hoc test. Results. Ischemia increased the locomotor activity and rearing behavior that were partly reversed by ω3. Ischemia decreased striatal DA and DOPAC contents and increased NE contents, effects reversed by ω3. This drug protected hippocampal neuron degeneration, as observed by Fluoro-Jade staining, and the increased immunostainings for TNF-alpha, COX-2, and iNOS were partly or totally blocked by ω3. Conclusion. This study showed a neuroprotective effect of ω3, in great part due to its anti-inflammatory properties, stimulating translational studies focusing on its use in clinic for stroke managing.

Original Research: The expression of MMP2 and MMP9 in the hippocampus and cerebral cortex of newborn mice under maternal lead exposure

The current study focused on the MMP2 and MMP9 expression in cerebral cortex and hippocampus of newborn mice under maternal lead exposure. Lead exposure was initiated from gestation to weaning. Lead acetate was dissolved in deionized water with concentration of 0.1, 0.2, and 0.5% and was absorbed through daily drinking. On day 21 after birth, lead in blood and tissue levels was examined by Graphite Furnace Atomic Absorption Spectrum (GFAAS). The protein expressions of MMP2 and MMP9 in hippocampus and cerebral cortex tissues were tested by western blotting and immunohistochemistry. Compared to the control group, blood, cerebral cortex, and hippocampus lead levels of newborn mice in 0.1, 0.2, and 0.5% lead exposure groups were markedly high (P < 0.05), and mice within the 0.2 and 0.5% lead exposure groups performed much worse than that of the control group in Water Maze test (P < 0.05). Compared with the control group, MMP2 and MMP9 expressions in hippocampus were up-regulated in the lead exposure groups (P < 0.05), and the MMP2 and MMP9 expressions in cerebral cortex were also higher (P < 0.05). The increased expression of MMP2 and MMP9 in the hippocampus and cerebral cortex may lead to the neurotoxicity in the context of maternal lead exposure.

Decreased IDE and IGF2 expression but increased Aβ40 in the cerebral cortex of mouse pups by early life lead exposure

As the abbreviation of plumbum and a chemical symbol for lead, Pb produces neurotoxic effects, which result into an impairment of learning and memory and other neurological dysfunctions. However, the mechanism of neurotoxicity of Pb exposure is unclear. The present study was undertaken to investigate the effects of maternal lead exposure on expression of insulin-degrading enzyme (IDE),insulin-like growth factor 2 (IGF2) and beta amyloid protein 40 (Aβ40) in the cerebral cortex of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.2% and 0.5% groups respectively. On the 21st postnatal day, On the PND21, the learning and memory ability were tested by water maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IDE, IGF2 and Aβ40 in cerebral cortex was examined by immunohistochemistry, immunofluorescence and western blotting. The lead levels in blood and cerebral cortex of all lead exposure groups were significantly higher than that of the control group (P<0.05). In water maze test, the performances of 0.5% and 1% lead exposure groups were worse than that of the control group (P<0.05).The expression of IDE and IGF2 was decreased, but Aβ40 was increased in lead exposed groups than that of the control group (P<0.05). The decreased expression of IDE and IGF2 and increased expression of Aβ40 in the cerebral cortex of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

New GABAergic Neurogenesis in the Hippocampal CA1 Region of a Gerbil Model of Long-Term Survival after Transient Cerebral Ischemic Injury

We investigated the probability of newly generated neurons that could survive and mature in the ischemic hippocampal CA1 region (CA1) of a gerbil model of transient cerebral ischemia. Neuronal death was shown in the stratum pyramidale (SP) from 4 days post-ischemia, and a significant increase in NeuN-positive ((+) ) neurons was found in the SP at 180 days post-ischemia. 5-Bromo-2-deoxyuridine (BrdU)(+) cells were co-stained with NeuN and glutamic decarboxylase 67 (GAD67). Brain-derived neurotrophic factor (BDNF) immunoreactivity and protein level was shown in nonpyramidal cells from 4 days post-ischemia, and the immunoreactivity was strong at 30 days post-ischemia and not significantly changed until 180 days post-ischemia. Furthermore, TrkB immunoreactivity was co-stained with GAD67 when we examined at 180 days post-ischemia. Myelin basic protein (MBP)(+) nerve fibers were reduced at 4 days post-ischemia and maintained until 60 days post-ischemia, and MBP immunoreactivity and levels were significantly increased at 180 days post-ischemia. In the passive avoidance test, cognitive dysfunction was improved at 180 days post-ischemia. These results suggest that the differentiation of neural progenitor cells into new GABAergic neurons may be promoted via BDNF in the ischemic CA1 and that the neurogenesis may partially mediate the recovery of cognitive impairments via increasing myelinated nerve fibers.

The hippocampus in aging and disease: From plasticity to vulnerability

The hippocampus has a pivotal role in learning and in the formation and consolidation of memory and is critically involved in the regulation of emotion, fear, anxiety, and stress. Studies of the hippocampus have been central to the study of memory in humans and in recent years, the regional specialization and organization of hippocampal functions have been elucidated in experimental models and in human neurological and psychiatric diseases. The hippocampus has long been considered a classic model for the study of neuroplasticity as many examples of synaptic plasticity such as long-term potentiation and -depression have been identified and demonstrated in hippocampal circuits. Neuroplasticity is the ability to adapt and reorganize the structure or function to internal or external stimuli and occurs at the cellular, population, network or behavioral level and is reflected in the cytological and network architecture as well as in intrinsic properties of hippocampal neurons and circuits. The high degree of hippocampal neuroplasticity might, however, be also negatively reflected in the pronounced vulnerability of the hippocampus to deleterious conditions such as ischemia, epilepsy, chronic stress, neurodegeneration and aging targeting hippocampal structure and function and leading to cognitive deficits. Considering this framework of plasticity and vulnerability, we here review basic principles of hippocampal anatomy and neuroplasticity on various levels as well as recent findings regarding the functional organization of the hippocampus in light of the regional vulnerability in Alzheimer's disease, ischemia, epilepsy, neuroinflammation and aging.

Spatial learning in men undergoing alcohol detoxification

Alcohol dependence is a major public health problem worldwide. Brain and behavioral disruptions including changes in cognitive abilities are common features of alcohol addiction. Thus, the present study was aimed to investigate spatial learning and memory in 29 alcoholic men undergoing alcohol detoxification by using a virtual Morris maze task. As age-matched controls we recruited 29 men among occasional drinkers without history of alcohol dependence and/or alcohol related diseases and with a negative blood alcohol level at the time of testing. We found that the responses to the virtual Morris maze are impaired in men undergoing alcohol detoxification. Notably they showed increased latencies in the first movement during the trials, increased latencies in retrieving the hidden platform and increased latencies in reaching the visible platform. These findings were associated with reduced swimming time in the target quadrant of the pool where the platform had been during the 4 hidden platform trials of the learning phase compared to controls. Such increasing latency responses may suggest motor control, attentional and motivational deficits due to alcohol detoxification.

Caffeic acid protects mice from memory deficits induced by focal cerebral ischemia

Brain ischemia pathophysiology involves a complex cascade of events such as inflammation and oxidative stress that lead to neuronal loss and cognitive deficits. Caffeic acid (CA) is a natural phenolic compound with antioxidant and anti-inflammatory properties. To evaluate the neuroprotective efficacy of this compound in mice subjected to a permanent middle cerebral artery occlusion, animals were pretreated and post-treated with CA, 2, 20, and 60 mg/kg/day, intraperitoneally, at 24, 48, 72, 96, or 120 h after ischemia. Animals were evaluated at 24 h after the permanent middle cerebral artery occlusion for brain infarction and neurological deficit score. At 72 h after the occlusion, animals were evaluated for locomotor activity, working memory, and short-term aversive memory; long-term aversive memory was evaluated 24 h after the evaluation of short-term aversive memory. Finally, at 120 h after the event, spatial memory and the expression levels of synaptophysin (SYP), SNAP-25, and caspase 3 were evaluated. The treatment with CA reduced the infarcted area and improved neurological deficit scores. There was no difference in locomotor activity between groups. The working, spatial, and long-term aversive memory deficits improved with CA. Furthermore, western blotting data showed that the expression of SYP, which correlates with synaptic formation and function, decreased after ischemic insult, and CA inhibited the reduction of SYP expression. Ischemia also increased, and CA treatment decreased, caspase 3 expression. These results suggest that CA exerts neuroprotective and antidementia effects, at least in part, by preventing the loss of neural cells and synapses in ischemic brain injury.

Alternative neural circuitry that might be impaired in the development of Alzheimer disease

It is well established that some individuals with normal cognitive capacity have abundant senile plaques in their brains. It has been proposed that those individuals are resilient or have compensation factors to prevent cognitive decline. In this comment, we explore an alternative mechanism through which cognitive capacity is maintained. This mechanism could involve the impairment of alternative neural circuitry. Also, the proportion of molecules such as Aβ or tau protein present in different areas of the brain could be important.

Modulation effects of cordycepin on the skeletal muscle contraction of toad gastrocnemius muscle

Isolated toad gastrocnemius muscle is a typical skeletal muscle tissue that is frequently used to study the motor system because it is an important component of the motor system. This study investigates the effects of cordycepin on the skeletal muscle contractile function of isolated toad gastrocnemius muscles by electrical field stimulation. Results showed that cordycepin (20 mg/l to 100 mg/l) significantly decreased the contractile responses in a concentration-dependent manner. Cordycepin (50 mg/l) also produced a rightward shift of the contractile amplitude-stimulation intensity relationship, as indicated by the increases in the threshold stimulation intensity and the saturation stimulation intensity. However, the most notable result was that the maximum amplitude of the muscle contractile force was significantly increased under cordycepin application (122±3.4% of control). This result suggests that the skeletal muscle contractile function and muscle physical fitness to the external stimulation were improved by the decreased response sensitivity in the presence of cordycepin. Moreover, cordycepin also prevented the repetitive stimulation-induced decrease in muscle contractile force and increased the recovery amplitude and recovery ratio of muscle contraction. However, these anti-fatigue effects of cordycepin on muscle contraction during long-lasting muscle activity were absent in Ca2+-free medium or in the presence of all Ca2+ channels blocker (0.4 mM CdCl2). These results suggest that cordycepin can positively affect muscle performance and provide ergogenic and prophylactic benefits in decreasing skeletal muscle fatigue. The mechanisms involving excitation-coupled Ca2+ influxes are strongly recommended.

The effects of early life Pb exposure on the expression of IL1-β, TNF-α and Aβ in cerebral cortex of mouse pups

OBJECTIVE

To investigate the effects of maternal lead (Pb) exposure on the learning and memory ability and expression of interleukin1-β (IL1-β), tumor necrosis factor (TNF-α) and beta amyloid protein (Aβ) in cerebral cortex of mice offspring.

METHODS

Pb exposure initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups, respectively. On the PND21, the learning and memory ability were tested by water maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IL1-β, TNF-α and Aβ in cerebral cortex was measured by immunohistochemistry and western blotting.

RESULTS

The Pb levels in blood and cerebral cortex of all exposure groups were significantly higher than that of the control group (P<0.05). In water maze test, the performances of 0.5% and 1% groups were worse than that of the control group (P<0.05). The expression of IL1-β, TNF-α and Aβ was increased in Pb exposed groups than that of the control group (P<0.05).

CONCLUSIONS

The high expression of IL1-β, TNF-α and Aβ in the cerebral cortex of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

The effects of early life lead exposure on the expression of insulin-like growth factor 1 and 2 (IGF1, IGF2) in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of IGF1 and IGF2 in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups respectively. On the 21st postnatal day, the learning and memory ability was tested by Water Maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IGF1 and IGF2 in hippocampus was examined by immunohistochemistry and western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than that of the control group (P<0.05). In Water Maze test, the performances of 0.5% and 1% lead exposure groupswere worse than that of the control group (P<0.05). The expression of IGF1 and IGF2 was decreased in lead exposed groups than that of the control group (P<0.05). The low expression of IGF1 and IGF2 in the hippocampus of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

Cordycepin suppresses excitatory synaptic transmission in rat hippocampal slices via a presynaptic mechanism

AIMS

Cordycepin plays an important role in modulating the function of central nervous system (CNS). However, the modulating mechanism is poorly understood. Excitatory synaptic transmission, the essential process in brain physiology and pathology, is critical in the signal integration activities of the CNS. To further understand the effects of cordycepin on CNS, we investigated the effects of cordycepin on excitatory synaptic transmission in the CA1 region of rat hippocampal slices.

METHODS

The effects of cordycepin on excitatory synaptic transmission were investigated by using in vitro field potential electrophysiology and whole-cell patch clamp techniques.

RESULTS

Cordycepin significantly decreased the amplitudes of field excitatory postsynaptic potentials (fEPSPs) elicited in the CA1 by stimulation of the Schaffer-commissural fibers. And the reduction in fEPSPs amplitude was associated with an increase in the paired-pulse facilitation. Cordycepin also suppressed α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and N-methyl-d-aspartic acid (NMDA) receptor-mediated responses but did not directly affect AMPA receptors and NMDA receptors. Furthermore, quantal analysis revealed that cordycepin decreased the frequency but not amplitude of miniature spontaneous excitatory postsynaptic currents.

CONCLUSIONS

These results demonstrate that cordycepin suppresses excitatory synaptic transmission by decreasing the excitatory neurotransmitter release presynaptically, which provides an evidence for the novel potential mechanism of cordycepin in modulating the function of CNS.

Hippocampal magnetic resonance imaging abnormalities in cardiac arrest are associated with poor outcome

BACKGROUND

The role of neuroimaging in assessing prognosis in comatose cardiac survivors appears promising, but little is known regarding the import of particular spatial patterns. We report a specific spatial imaging abnormality on magnetic resonance imaging (MRI) that portends a poor prognosis: bilateral hippocampal hyperintensities on diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences.

METHODS

Eighty sequential comatose cardiac arrest patients underwent MRI scans. Qualitative and quantitative regional analyses were performed. Patients were categorized as HIPPO(+) (n = 18) or HIPPO(-) (n = 62) based on whether they had bilateral hippocampal hyperintensities. Poor outcome was defined by a modified Rankin Scale (mRS) score ≥4 at 6 months.

RESULTS

Patients with bilateral hippocampal abnormalities had a higher frequency of poor outcome (P = .032). HIPPO(+) patients suffered more severe cerebral injury, with lower whole brain apparent diffusion coefficient values (P = .043) and a greater number of affected regions on DWI (P = .001) and FLAIR (P = .001) than HIPPO(-) patients. The hippocampal approach was 100% specific for a poor prognosis; only 1 patient survived and remained in a vegetative state.

CONCLUSIONS

Bilateral hippocampal hyperintensities on MRI may be a specific imaging finding that is indicative of poor prognosis in patients who suffer global hypoxic-ischemic injury. More research on the prognostic significance of this and similar neuroimaging patterns is indicated.

Sustained expression of osteopontin is closely associated with calcium deposits in the rat hippocampus after transient forebrain ischemia

The present study was designed to evaluate the extent and topography of osteopontin (OPN) protein expression in the rat hippocampus 4 to 12 weeks following transient forebrain ischemia, and to compare OPN expression patterns with those of calcium deposits and astroglial and microglial reactions. Two patterns of OPN staining were recognized by light microscopy: 1) a diffuse pattern of tiny granular deposits throughout the CA1 region at 4 weeks after ischemia and 2) non-diffuse ovoid to round deposits, which formed conglomerates in the CA1 pyramidal cell layer over the chronic interval of 8 to 12 weeks. Immunogold-silver electron microscopy and electron probe microanalysis demonstrated that OPN deposits were indeed diverse types of calcium deposits, which were clearly delineated by profuse silver grains indicative of OPN expression. Intracellular OPN deposits were frequently observed within reactive astrocytes and neurons 4 weeks after ischemia but rarely at later times. By contrast, extracellular OPN deposits progressively increased in size and appeared to be gradually phagocytized by microglia or brain macrophages and some astrocytes over 8 to 12 weeks. These data indicate an interaction between OPN and calcium in the hippocampus in the chronic period after ischemia, suggesting that OPN binding to calcium deposits may be involved in scavenging mechanisms.

Anti-inflammatory cytokines, TGF-β1 and IL-10, exert anti-hypoxic action and abolish posthypoxic hyperexcitability in hippocampal slice neurons: comparative aspects

The aim of this study was to investigate the comparative effects of transforming growth factor β1 (TGF-β1) and interleukin-10 (IL-10) on the repeated brief hypoxia-induced alterations in the activity of hippocampal slice CA1 pyramidal neurons. The method of field potentials measurement in CA1 region of hippocampal slices was used. The principal results of our work are summarized as follow. 1. TGF-β1 reduces the depressive effect of brief hypoxia on the population spike amplitude more effectively than IL-10. 2. During TGF-β1 exposure (in contrast to IL-10), three 3-min hypoxic episodes do not induce the rapid hypoxic preconditioning. 3. TGF-β1 and IL-10 equally abolish posthypoxic hyperexcitability induced by repeated brief episodes of hypoxia in CA1 pyramidal neurons. These findings indicated that TGF-β1 and IL-10 are able to evoke anti-hypoxic effect and abolish the development of posthypoxic hyperexcitability induced by repeated brief hypoxic episodes in hippocampal CA1 pyramidal neurons. Our results also demonstrated that TGF-β1 reduced the effectiveness of hypoxia to depress neuronal activity more effectively than IL-10. We suggest that the present findings allow to explain the certain neuroprotective mechanisms of IL-10 and TGF-beta1 in the early phase of hypoxia and indicate that a therapeutic anti-inflammatory approach using these substances can provide neuroprotection in the brain hypoxic conditions.

Cordycepin decreases activity of hippocampal CA1 pyramidal neuron through membrane hyperpolarization

Cordycepin (3'-deoxyadenosine) is the main functional component of Cordycepins militaris, a renowned traditional Chinese medicine, which has been shown to possess anti-tumor, anti-inflammatory, anti-diabetic and neuro-protective effects. However, the effect of cordycepin on the central nervous system (CNS) remains unclear. In this study, the effects of cordycepin on neuronal activity were investigated on the CA1 pyramidal neurons in rat hippocampal brain slices using a whole-cell patch clamp technique. Our results revealed that cordycepin significantly decreased the frequency of both the spontaneous and evoked action potential (AP) firing. While AP spike width, the amplitude of fast after hyperpolarization (fAHP), and membrane input resistance were not altered by cordycepin, the neuronal membrane potential was hyperpolarized by cordycepin. Collectively, these results demonstrate that cordycepin reduces neuronal activity by inducing membrane hyperpolarization, indicating that cordycepin may be a potential therapeutic strategy for ischemic and other excitotoxic disorders.

Therapeutic hypothermia influences cell genesis and survival in the rat hippocampus following global ischemia

Delayed hypothermia salvages CA1 neurons from global ischemic injury. However, the effects of this potent neuroprotectant on endogenous repair mechanisms, such as neurogenesis, have not been clearly examined. In this study, we quantified and phenotyped newly generated cells within the hippocampus following untreated and hypothermia-treated ischemia. We first show that CA1 pyramidal neurons did not spontaneously regenerate after ischemia. We then compared the level of neuroprotection when hypothermia was initiated either during or after ischemia. Treatment efficacy decreased with longer delays, but hypothermia delayed for up to 12 hours was neuroprotective. Although bromodeoxyuridine (BrdU) incorporation was elevated in ischemic groups, CA1 neurogenesis did not occur as the BrdU label did not colocalize with neuronal nuclei (NeuN) in any of the groups. Instead, the majority of BrdU-labeled cells were Iba-positive microglia, and neuroprotective hypothermia decreased the delayed generation of microglia during the third postischemic week. Conversely, hypothermia delayed for 12 hours significantly increased the survival of newly generated dentate granule cells at 4 weeks after ischemia. Thus, our findings show that CA1 neurogenesis does not contribute to hypothermic neuroprotection. Importantly, we also show that prolonged hypothermia positively interacts with postischemic repair processes, such as neurogenesis, resulting in improved functional outcome.

Changes in HPA reactivity and noradrenergic functions regulate spatial memory impairments at delayed time intervals following cerebral ischemia

This study investigates the association of ischemia-induced spatial memory impairment to alterations of the HPA axis and noradrenergic activation post insult. Experiment 1 characterized the effects of 10 min forebrain ischemia on corticosterone (CORT) secretion following ischemia and in response to spatial memory assessment in the Barnes maze, as well as the impact of pre-ischemia treatment with the glucocorticoid inhibitor metyrapone (175 mg/kg; s.c.). The results showed that cerebral ischemia represents a significant physiological stressor that upregulated CORT secretion 1, 24 and 72 h post-ischemia but not at 7 days. In response to testing in the Barnes maze ischemic animals showed elevated CORT secretion simultaneously with spatial memory deficits. The single dose of metyrapone attenuated the ischemia-induced adrenocortical hyper-responsiveness and subsequent memory deficits despite not providing neuroprotection in the hippocampal CA1 pyramidal cells. To complement these findings, we examined whether norepinephrine which provides positive feedback to the HPA axis and is upregulated following brain ischemia could influence memory performance at delayed intervals after ischemia. Experiment 2 demonstrated that pre-testing administration of the alpha2-adrenoceptor agonist clonidine (.04 mg/kg, s.c.) attenuated ischemia-induced working memory impairments in a radial maze while opposite effects were obtained with the antagonist yohimbine (.3 mg/kg, s.c.). Post-testing administration of clonidine produced spatial reference memory impairments in ischemic rats. The findings from the current study demonstrate increased sensitization and responsiveness of systems regulating stress hormones at long intervals post ischemia. Importantly, we demonstrate that these effects contribute to post ischemic cognitive impairments which can be attenuated pharmacologically even in the presence of hippocampal degeneration at time of testing.

Chronic cerebral ischaemia forms new cholinergic mechanisms of learning and memory

The purpose of this research was a comparative analysis of cholinergic synaptic organization following learning and memory in normal and chronic cerebral ischaemic rats in the Morris water maze model. Choline acetyltransferase and protein content were determined in subpopulations of presynapses of “light” and “heavy” synaptosomal fractions of the cortex and the hippocampus, and the cholinergic projective and intrinsic systems of the brain structures were taken into consideration. We found a strong involvement of cholinergic systems, both projective and intrinsic, in all forms of cognition. Each form of cognition had an individual cholinergic molecular profile and the cholinergic synaptic compositions in the ischaemic rat brains differed significantly from normal ones. Our data demonstrated that under ischaemic conditions, instead of damaged connections new key synaptic relationships, which were stable against pathological influences and able to restore damaged cognitive functions, arose. The plasticity of neurochemical links in the individual organization of certain types of cognition gave a new input into brain pathology and can be used in the future for alternative corrections of vascular and other degenerative dementias.

Long-term survival of human neural stem cells in the ischemic rat brain upon transient immunosuppression

Understanding the physiology of human neural stem cells (hNSCs) in the context of cell therapy for neurodegenerative disorders is of paramount importance, yet large-scale studies are hampered by the slow-expansion rate of these cells. To overcome this issue, we previously established immortal, non-transformed, telencephalic-diencephalic hNSCs (IhNSCs) from the fetal brain. Here, we investigated the fate of these IhNSC's immediate progeny (i.e. neural progenitors; IhNSC-Ps) upon unilateral implantation into the corpus callosum or the hippocampal fissure of adult rat brain, 3 days after global ischemic injury. One month after grafting, approximately one fifth of the IhNSC-Ps had survived and migrated through the corpus callosum, into the cortex or throughout the dentate gyrus of the hippocampus. By the fourth month, they had reached the ipsilateral subventricular zone, CA1-3 hippocampal layers and the controlateral hemisphere. Notably, these results could be accomplished using transient immunosuppression, i.e administering cyclosporine for 15 days following the ischemic event. Furthermore, a concomitant reduction of reactive microglia (Iba1+ cells) and of glial, GFAP+ cells was also observed in the ipsilateral hemisphere as compared to the controlateral one. IhNSC-Ps were not tumorigenic and, upon in vivo engraftment, underwent differentiation into GFAP+ astrocytes, and β-tubulinIII+ or MAP2+ neurons, which displayed GABAergic and GLUTAmatergic markers. Electron microscopy analysis pointed to the formation of mature synaptic contacts between host and donor-derived neurons, showing the full maturation of the IhNSC-P-derived neurons and their likely functional integration into the host tissue. Thus, IhNSC-Ps possess long-term survival and engraftment capacity upon transplantation into the globally injured ischemic brain, into which they can integrate and mature into neurons, even under mild, transient immunosuppressive conditions. Most notably, transplanted IhNSC-P can significantly dampen the inflammatory response in the lesioned host brain. This work further supports hNSCs as a reliable and safe source of cells for transplantation therapy in neurodegenerative disorders.

Triggered by asphyxia neurogenesis seems not to be an endogenous repair mechanism, gliogenesis more like it

We analyzed the long-term consequences of asphyxial cardiac arrest for hippocampal cell proliferation in rats to evaluate if the ischaemia-induced degenerated CA1 region may be repopulated by endogenous (stem) cells. Studies were performed in an asphyxial cardiac arrest model with 5 minutes of asphyxiation and three different survival times: 7, 21, and 90 days. Sham-operated non-asphyxiated rats served as control. Cell proliferation was studied by labeling dividing cells with 5-bromo-2'-deoxy-uridine (BrdU). The neurodegenerative/regenerative pattern at single cell levels was monitored by immunohistochemistry. Alterations of gene expression were analyzed by real-time quantitative RT-PCR. Analysis of BrdU-incorporation demonstrated an increase at 7, 21 as well as 90 days after global ischaemia in the hippocampal CA1 pyramidal cell layer. Similar results were found in the dentate gyrus. Differentiation of BrdU-positive cells, investigated by cell phenotype-specific double fluorescent labeling, showed increased neurogenesis only in the dentate gyrus of animals surviving the cardiac arrest for 7 days. The majority of newcomers, especially in the damaged CA1 region, consisted of glial cells. Moreover, asphyxia seemed to be able to induce the migration of microglia and astroglia from adjacent areas into the damaged area and/or the activation of resident cells. In addition, we show microglia proliferation/activation even 90 days after cardiac arrest. This morphological finding was confirmed by PCR analysis. The results indicate that asphyxia triggers cell proliferation in general and gliogenesis in particular - a possible pro-reparative event. Furthermore, from the finding of microglia proliferation up to 90 days after insult we conclude that delayed cell death processes take place which should be considered for further therapy strategies.

Eszopiclone prevents excitotoxicity and neurodegeneration in the hippocampus induced by experimental apnea

STUDY OBJECTIVE

This study was designed to determine the effects of eszopiclone on apnea-induced excitotoxic synaptic processes and apoptosis in the hippocampus.

DESIGN

Recurrent periods of apnea, which consisted of a sequence of apnea (75% SpO2), followed by ventilation with recovery to normoxia (> 95% SpO2), were induced for a period of three hours in anesthetized guinea pigs. The CA3 Schaffer collateral pathway in the hippocampus was stimulated and the field excitatory postsynaptic potential (fEPSP) response was recorded in CA1. Animals in the experimental group received an intravenous injection of eszopiclone (3 mg/kg) 10 min prior to the initiation of the periods of recurrent apnea, and once every 60 min thereafter; control animals received comparable injections of vehicle. At the end of the 3-h period of recurrent apnea, the animals were perfused, and hippocampal sections were immunostained in order to determine the presence of apoptosis, i.e., programmed cell death. ANALYSES AND RESULTS: Apnea resulted in a persistent increase in synaptic responsiveness of CA1 neurons as determined by analyses of the fEPSP. Eszopiclone antagonized the apnea-induced increase in the fEPSP. Morphological analyses revealed significant apoptosis of CA1 neurons in control animals; however, there was no significant apoptosis in eszopiclone-treated animals.

CONCLUSIONS

Eszopiclone was determined to suppress the apnea-induced hyperexcitability of hippocampal CA1 neurons, thereby reducing/eliminating neurotoxicity. These data lend credence to our hypothesis that eszopiclone, exclusive of its hypnotic actions, has the capacity to function as a potent neuroprotective agent.

Agonist-induced restoration of hippocampal neurogenesis and cognitive improvement in a model of cholinergic denervation

Loss of basal forebrain cholinergic innervation of the hippocampus and severe neuronal loss within the hippocampal CA1 region are early hallmarks of Alzheimer's disease, and are strongly correlated with cognitive status. Various therapeutic approaches involve attempts to enhance neurotransmission or to provide some level of neuroprotection for remaining cells. An alternative approach may involve the generation of new cells to replace those lost in AD. Indeed, a simple shift in the balance between cell generation and cell loss may slow disease progression and possibly even reverse existing cognitive deficits. One potential neurogenic regulator might be acetylcholine, itself, which has been shown to play a critical role in hippocampal development. Here, we report the effects of various cholinergic compounds on indices of hippocampal neurogenesis, demonstrating a significant induction following pharmacological activation of muscarinic M1 receptors, located on hippocampal progenitors in the adult brain. This is the first report that a small-molecule agonist may induce neurogenesis in the hippocampal CA1 region. Furthermore, such treatment reversed deficits in markers of neurogenesis and spatial working memory triggered by cholinergic denervation in a rodent model. This study suggests the use of small molecule, receptor agonists may represent a novel means to trigger the restoration of specific neuronal populations lost to a variety of neurodegenerative disorders, such as Parkinson's, Alzheimer's, Huntington's and Amyotrophic Lateral Sclerosis.

Persistent behavioral impairments and neuroinflammation following global ischemia in the rat

Cognitive deficits associated with cardiac arrest have been well documented; however, the corresponding deficits in animal models of global ischemia have not been comprehensively assessed, particularly after long-term, clinically relevant survival times. We exposed male Sprague-Dawley rats to 10 min of bilateral carotid artery occlusion + systemic hypotension (40-45 mmHg) or sham surgery, and used histopathological assessments for short-term survival animals (16 days) and both behavioral and histopathological assessments for long-term survival animals (270 days). Analyses revealed significant long-term deficits in ischemic animals' learning, memory (T-maze, radial arm maze), working memory (radial arm maze), and reference memory (Morris water maze, radial arm maze) abilities that were not associated with a general cognitive decline. Histological results showed significant increases in glial fibrillary acidic protein, neuron glia 2, OX-42 and ED-1 staining, as well as significant decreases in microtubule-associated protein 2 staining and cornu ammonis area 1 (CA1) cell counts 16 days post-ischemia. The pattern at 270 days was similar, but notably there was a persistent elevation of ED-1 staining, suggesting recent cell death as well as significant atrophy of CA1. Whereas previous work has primarily reported transient changes in behavior after global ischemia, this study describes disturbances in several different functional domains following CA1 cell loss at clinically relevant survival times. Moreover, the histopathological outcome is suggestive of a spontaneous repopulation of CA1, but this was not sufficient to offset the behavioral impairments arising from the ischemic insult.