Exercise-induced Nitric Oxide Contributes to Spatial Memory and Hippocampal Capillaries in Rats.

Exercise has been argued to improve cognitive function in both humans and rodents. Angiogenesis significantly contributes to brain health, including cognition. The hippocampus is a crucial brain region for cognitive function. However, studies quantifying the capillary changes in the hippocampus after running exercise are lacking. Moreover, the molecular details underlying the effects of running exercise remain poorly understood. We show that endogenous nitric oxide contributes to the beneficial effects of running exercise on cognition and hippocampal capillaries. Four weeks of running exercise significantly improved spatial memory ability and increased the number of capillaries in the cornu ammonis 1 subfield and dentate gyrus of Sprague-Dawley rats. Running exercise also significantly increased nitric oxide synthase activity and nitric oxide content in the rat hippocampus. After blocking the synthesis of endogenous nitric oxide by lateral ventricular injection of NG-nitro-L-arginine methyl ester, a nonspecific nitric oxide synthase inhibitor, the protective effect of running exercise on spatial memory was eliminated. The protective effect of running exercise on angiogenesis in the cornu ammonis 1 subfield and dentate gyrus of rats was also absent after nitric oxide synthase inhibition. Therefore, during running excise, endogenous nitric oxide may contribute to regulating spatial memory ability and angiogenesis in cornu ammonis 1 subfield and dentate gyrus of the hippocampus.

Cerebral Blood Flow-Guided Manipulation of Arterial Blood Pressure Attenuates Hippocampal Apoptosis After Asphyxia-Induced Cardiac Arrest in Rats.

Background In most post-cardiac arrest patients, the autoregulation mechanism of cerebral blood flow (CBF) is dysregulated. We examined whether recovery of CBF by adjusting mean arterial pressure mitigates post-cardiac arrest neuronal damage. Methods and Results Wistar rats that underwent 8-minute asphyxia-induced cardiac arrest and resuscitation were computer-randomized to norepinephrine or control groups. The CBF was measured at the dorsal hippocampal CA1 region of the left hemisphere. In the norepinephrine group, the mean arterial pressure was adjusted to recover CBF to 80% to 100% of baseline. Twenty-four hours following resuscitation, neurological outcomes were assessed, and brain tissues and blood samples were harvested for neuronal apoptosis and injury assessment. Thirty resuscitated rats were randomized into 2 groups, each containing 12 rats that completed the experiments. Norepinephrine infusion effectively prevented posthyperemia hypoperfusion and recovered CBF to pre-arrest baseline levels; a moderate positive linear correlation between mean arterial pressure and CBF during this period was also observed (P<0.001). There were no significant between-group differences in neurological recovery. In the norepinephrine group compared with the control group, upregulated cleaved caspase-3 protein expression in brain tissue determined by Western blot was reduced (P=0.02) and the densities of apoptotic cells in hippocampal CA1 and CA3 regions determined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick-end labeling were decreased (P<0.001). No significant differences in serum neuron-specific enolase or S100ß levels were detected between the 2 groups. Conclusions CBF recovery demonstrated neuroprotective effects by reducing activation of cerebral apoptosis and number of apoptotic neurons. However, these effects did not significantly improve clinical neurological function, necessitating further investigation.

Rhythmic light flicker rescues hippocampal low gamma and protects ischemic neurons by enhancing presynaptic plasticity.

The complex relationship between specific hippocampal oscillation frequency deficit and cognitive dysfunction in the ischemic brain is unclear. Here, using a mouse two-vessel occlusion (2VO) cerebral ischemia model, we show that visual stimulation with a 40 Hz light flicker drove hippocampal CA1 slow gamma and restored 2VO-induced reduction in CA1 slow gamma power and theta-low gamma phase-amplitude coupling, but not those of the high gamma. Low gamma frequency lights at 30 Hz, 40 Hz, and 50 Hz, but not 10 Hz, 80 Hz, and arrhythmic frequency light, were protective against degenerating CA1 neurons after 2VO, demonstrating the importance of slow gamma in cognitive functions after cerebral ischemia. Mechanistically, 40 Hz light flicker enhanced RGS12-regulated CA3-CA1 presynaptic N-type calcium channel-dependent short-term synaptic plasticity and associated postsynaptic long term potentiation (LTP) after 2VO. These results support a causal relationship between CA1 slow gamma and cognitive dysfunctions in the ischemic brain.

Local hippocampal fast gamma rhythms precede brain-wide hyperemic patterns during spontaneous rodent REM sleep.

Rapid eye movement sleep (REMS) is a peculiar brain state combining the behavioral components of sleep and the electrophysiological profiles of wake. After decades of research our understanding of REMS still is precluded by the difficulty to observe its spontaneous dynamics and the lack of multimodal recording approaches to build comprehensive datasets. We used functional ultrasound (fUS) imaging concurrently with extracellular recordings of local field potentials (LFP) to reveal brain-wide spatiotemporal hemodynamics of single REMS episodes. We demonstrate for the first time the close association between global hyperemic events - largely outmatching wake levels in most brain regions - and local hippocampal theta (6-10 Hz) and fast gamma (80-110 Hz) events in the CA1 region. In particular, the power of fast gamma oscillations strongly correlated with the amplitude of subsequent vascular events. Our findings challenge our current understanding of neurovascular coupling and question the evolutionary benefit of such energy-demanding patterns in REMS function.

Effects of Lipoxin A4 Pretreatment on Cognitive Function of Aged Rats after Global Cerebral Ischemia Reperfusion.

The aim of the present study was to investigate the effect of lipoxin A4 (LXA4) pretreatment on cognitive function of aged rats after global cerebral ischemia reperfusion, and to explore its possible mechanism. Thirty-six aged male Sprague-Dawley rats were randomly divided into three groups (n=2 each): sham-operation group (S group), global cerebral ischemia reperfusion group (I/R group) and LXA4-pretreatment group (L group). The rat model of global cerebral ischemia reperfüsion was established by occlusion of the bilateral common carotid artery with hypotension. The cognitive function of rats was determined by a step-down type passive avoidance test and Morris Water Maze test on the third day after reperfUsion. Rats were sacrificed after Water Maze test and the pathological changes of hippocampal CAI region were observed and the related inflammatory mediators were determined. As compared with S group, the escape latency in I/R group was prolonged from the first day to the fifth day, while that in L group was prolonged from the first day to the third day. The retention time in I/R group and L group in the first quadrant was shortened. The reaction time, frequency of reaction mistake and frequency of escape mistake in I/R group increased, and the latent period shortened. The frequency of escape mistake in L group increased, and the damage in the hippocampal CAI region of I/R group and L group was obvious. The levels of S-100ß, TNP-α, IL-lß, IL-10 and NF-κB in I/R group and L group increased. As compared with I/R group, the escape latency in L group was shortened from the first day to the fifth day, and the retention time in the first quadrant prolonged. The reaction time, frequency of reaction mistake and frequency of escape mistake in L group decreased, and the latent period prolonged. The damage in the hippocampal CAI region of L group was alleviated as well. The levels of S-100ß, TNP-α, IL-lß and NF-κB in L group decreased, and those of IL-10 increased. It can be concluded that LXA4 pretreatment can improve the cognitive function in aged rats after global cerebral ischemia reperfusion probably by inhibiting the inflammatory reaction.

Hippocampal microvasculature changes in association with oxidative stress in Alzheimer's disease.

Vascular endothelial dysfunction is a primary phenotype of aging, and microvascular (MV) lesion is mainly associated with Alzheimer's disease (AD). Here we have studied the correlation of MV wall thickness and CA1 pyramidal neuronal pathology in autopsy-confirmed AD brains. Both hyaline (h-MV) and increased cell number (c-MV) associated MV wall thickening was found in age-matched control (AC) hippocampus without significant change in Aß level (Braak stages 0-III). AC neurons neighboring the h-MV showed lower levels of oxidative DNA/RNA damage and Aß precursor protein (APP), while the neurons around c-MV showed higher oxidative DNA/RNA damage with increased APP expression. Neurons in AC hippocampus without MV wall thickening (thin wall) showed increased DNA/RNA damage and APP levels compared to AC cases with h-MV and c-MV walls. In the AD hippocampus neurons neighboring h-MV walls showed increased levels of Aß and decreased number of dendritic spines (at Braak stages IV-VI). C-MV neighboring neurons in the AD cases showed higher levels of DNA/RNA damage with increased APP at stages II - III, followed by lower levels of oxidative DNA/RNA damage, decreased APP and increased Aß levels with loss of dendritic spines at stages IV-VI. Prolonged treatment of primary human fetal hippocampal neurons with tert-butyl hydroperoxide (TBHP) induced oxidative DNA damage with a sustained increase in APP. Aß increased rapidly and then decreased overtime. Short-term TBHP treated neurons showed lower levels of superoxide (O2• -) without significant DNA damage. Short-term TBHP treatment induced a gradual decrease in APP but an increase in Aß levels over time. In conclusion this study indicates that AD hippocampus at Braak stages II-III are characterized by strong oxidative DNA/RNA damage with increased APP in neurons associated with c-MV, while stages IV-VI are characterized by a slow increase in Aß in neurons neighboring both h-MV and c-MV.

Effects of Memantine on Nitric Oxide Production and Hydroxyl Radical Metabolism during Cerebral Ischemia and Reperfusion in Mice.

BACKGROUND: The purpose of this study was to investigate the effects of memantine on brain ischemia. Because we can measure nitric oxide (NO) production and hydroxyl radical metabolism continuously, we investigated the effect of memantine on NO production and hydroxyl radical metabolism in cerebral ischemia and reperfusion. METHODS: Memantine (25 µmol/kg) was administered intraperitoneally to 6 C57BL/6 mice 30 minutes before ischemia. Seven additional mice received no injection (controls). NO production and hydroxyl radical metabolism were continuously monitored using bilateral striatal microdialysis in vivo. Hydroxyl radical formation was monitored using the salicylate trapping method. Forebrain ischemia was produced in all mice by occluding the common carotid artery bilaterally for 10 minutes. Levels of the NO metabolites nitrite (NO2-) and nitrate (NO3-) were determined using the Griess reaction. Survival rates of hippocampal CA1 neurons were calculated and 8-hydroxydeoxyguanosine (8-OHdG)-immunopositive cells were counted to evaluate the oxidative stress in hippocampal CA1 neurons 72 hours after the start of reperfusion. RESULTS: The regional cerebral blood flow was significantly higher in the memantine group than in the control group after reperfusion. Furthermore, the level of 2,3-dihydroxybenzoic acid was significantly lower in the memantine group than in the control group during ischemia and reperfusion. Levels of NO2- and NO3- did not differ significantly between the 2 groups. Although survival rates in the CA1 did not differ significantly, there were fewer 8-OHdG-immunopositive cells in animals that had received memantine than in control animals. CONCLUSIONS: These data suggest that memantine exerts partially neuroprotective effects against cerebral ischemic injury.

Chronic cerebral hypoperfusion induced by bilateral carotid artery stenosis causes selective recognition impairment in adult mice.

OBJECTIVES: Chronic cerebral hypoperfusion (CCH) can result in vascular dementia and small vessel white matter ischemic injury. These findings have previously been demonstrated in a murine experimental model of CCH secondary to bilateral common carotid artery stenosis (BCAS). This study sought to elucidate the effects of CCH on recognition memory as assessed by the novel object recognition (NOR) test and histological analysis of the hippocampus and perirhinal cortex. METHODS: Studies were performed on ten-week-old male mice using bilateral 0.18 mm microcoils to narrow the carotid arteries in accordance with prior publications. Following surgery, BCAS (n = 6) and sham (n = 6) mice were evaluated using NOR and 8-arm radial maze testing paradigms. Tissue damage was assessed using H&E staining on a parallel cohort of mice (n = 6 BCAS, n = 7 sham). RESULTS: In the NOR paradigm, BCAS mice demonstrated significant deficits in short-term memory. Consistent with prior studies, BCAS mice also performed significantly worse on 8-arm radial maze testing. BCAS mice exhibited significantly more neuronal injury in the perirhinal cortex when compared to sham-operated mice. However, no significant differences in neuronal damage were observed in the CA1 region of the hippocampus. DISCUSSION: Experimental CCH secondary to BCAS results in recognition memory deficits on NOR testing. Damage to the perirhinal cortex, rather than to the hippocampus, may underlie this impairment.

Autophagosome maturation mediated by Rab7 contributes to neuroprotection of hypoxic preconditioning against global cerebral ischemia in rats.

Autophagy disruption leads to neuronal damage in hypoxic-ischemic brain injury. Rab7, a member of the Rab GTPase superfamily, has a unique role in the regulation of autophagy. Hypoxic preconditioning (HPC) provides neuroprotection against transient global cerebral ischemia (tGCI). However, the underlying mechanisms remain poorly understood. Thus, the current study explored the potential molecular mechanism of the neuroprotective effect of HPC by investigating how Rab7 mediates autophagosome (AP) maturation after tGCI in adult rats. We found that HPC attenuated AP accumulation in the hippocampal CA1 region after tGCI via restoration of autophagic flux. We also confirmed that this HPC-induced neuroprotection was not caused by the increase in lysosomes or the improvement of lysosomal function after tGCI. Electron microscopic analysis then revealed an increase in autolysosomes in CA1 neurons of HPC rats. Moreover, the inhibition of autophagosome-lysosome fusion by chloroquine significantly aggravated neuronal death in CA1, indicating that AP maturation contributes to HPC-induced neuroprotection against neuronal injury after tGCI. Furthermore, the activation of Rab7 was found to be involved in the neuroprotective effect of AP maturation after HPC. At last, the knockdown of ultraviolet radiation resistance-associated gene (UVRAG) in vivo disrupted the interaction between Vps16 and Rab7, attenuated the activation of Rab7, interrupted autophagic flux, and ultimately abrogated the HPC-induced neuroprotection against tGCI. Our results indicated that AP maturation was enhanced by the activation of Rab7 via UVRAG-Vps16 interaction, which further demonstrated the potential neuroprotective role of Rab7 in HPC against tGCI-induced neuronal injury in adult rats.

EphA4 may contribute to microvessel remodeling in the hippocampal CA1 and CA3 areas in a mouse model of temporal lobe epilepsy.

Unclustered and pre-clustered ephrin-A5-Fc have identical anti-epileptic effects in the dentate gyrus of hippocampus in a mouse model of temporal lobe epilepsy (TLE), and act through alleviating ephrin receptor A4 (EphA4)­mediated neurogenesis and angiogenesis. However, the effects of ephrin­A5­Fcs on EphA4 and angiogenesis in Cornu Ammonis (CA)1 and CA3 areas remain unclear. In the present study, male C57BL/6 mice underwent pilocarpine­induced TLE. The expression of EphA4 and ephrin­A5 proteins was analyzed by immunohistochemistry, and the mean density and diameter of platelet endothelial cell adhesion molecule­1­labeled microvessels in CA1 and CA3 were calculated in the absence or presence of two types of ephrin­A5­Fc intrahippocampal infusion. Microvessels perpendicular to the pyramidal cell layer decreased; however, microvessels that traversed the layer increased, and became distorted and fragmented. The mean densities and diameters of microvessels gradually increased and remained greater than those in the control group at 56 days post­status epilepticus (SE). The upregulation of EphA4 and ephrin­A5 proteins began at 7 days and was maintained until 28 days, subsequently decreasing slightly at 56 days post­SE. Blockade of EphA4 by unclustered­ephrin­A5­Fc effected a reduction in the mean density and mean diameter of microvessels in the CA1 and CA3 areas; conversely, activation of EphA4 by clustered­ephrin­A5­Fc induced an increase in these values. Ephrin­A5 ligand binding to EphA4 receptor may contribute to angiogenesis during epileptogenesis in the hippocampal CA1 and CA3 areas.

The ameliorative effects of exercise on cognitive impairment and white matter injury from blood-brain barrier disruption induced by chronic cerebral hypoperfusion in adolescent rats.

Vascular dementia is the progressive change in blood vessels that leads to neuronal injuries in vulnerable areas induced by chronic cerebral hypoperfusion (CCH). CCH induces disruption of blood-brain barrier (BBB), and this BBB disruption can initiate the cognitive impairment and white matter injury. In the present study, we evaluated the effect of treadmill exercise on the cognitive impairment, white matter injury, and BBB disruption induced by CCH. Vascular dementia was induced by permanent bilateral common carotid arteries occlusion (BCCAO) in rats. The rats in the exercise group were made to run on a treadmill for 30min once a day for 14 weeks, starting 4 weeks after birth. Our results revealed that treadmill exercise group was alleviated the cognitive impairment and myelin degradation induced by CCH. The disruption of BBB after CCH indicates degradation of occludin, zonula occluden-1 (ZO-1), and up-regulation of matrix metalloproteinases (MMPs). Treadmill exercise may provide protective effects on BBB disruption from degradation of occludin, ZO-1, and overexpression of MMP-9 after CCH. These findings suggest that treadmill exercise ameliorates cognitive impairment and white matter injury from BBB disruption induced by CCH in rats. The present study will be valuable for means of prophylactic and therapeutic intervention for patients with CCH.

Mitochondrial dynamics following global cerebral ischemia.

Global brain ischemia/reperfusion induces neuronal damage in vulnerable brain regions, leading to mitochondrial dysfunction and subsequent neuronal death. Induction of neuronal death is mediated by release of cytochrome c (cyt c) from the mitochondria though a well-characterized increase in outer mitochondrial membrane permeability. However, for cyt c to be released it is first necessary for cyt c to be liberated from the cristae junctions which are gated by Opa1 oligomers. Opa1 has two known functions: maintenance of the cristae junction and mitochondrial fusion. These roles suggest that Opa1 could play a central role in both controlling cyt c release and mitochondrial fusion/fission processes during ischemia/reperfusion. To investigate this concept, we first utilized in vitro real-time imaging to visualize dynamic changes in mitochondria. Oxygen-glucose deprivation (OGD) of neurons grown in culture induced a dual-phase mitochondrial fragmentation profile: (i) fragmentation during OGD with no apoptosis activation, followed by fusion of mitochondrial networks after reoxygenation and a (ii) subsequent extensive fragmentation and apoptosis activation that preceded cell death. We next evaluated changes in mitochondrial dynamic state during reperfusion in a rat model of global brain ischemia. Evaluation of mitochondrial morphology with confocal and electron microscopy revealed a similar induction of fragmentation following global brain ischemia. Mitochondrial fragmentation aligned temporally with specific apoptotic events, including cyt c release, caspase 3/7 activation, and interestingly, release of the fusion protein Opa1. Moreover, we uncovered evidence of loss of Opa1 complexes during the progression of reperfusion, and electron microscopy micrographs revealed a loss of cristae architecture following global brain ischemia. These data provide novel evidence implicating a temporal connection between Opa1 alterations and dysfunctional mitochondrial dynamics following global brain ischemia.

Monitoring of cerebral blood flow during hypoxia-ischemia and resuscitation in the neonatal rat using laser speckle imaging.

Neonatal hypoxic-ischemic encephalopathy (HIE) is associated with alterations in cerebral blood flow (CBF) as a result of perinatal asphyxia. The extent to whichCBFchanges contribute to injury, and whether treatments that ameliorate these changes might be neuroprotective, is still unknown. Higher throughput techniques to monitorCBFchanges in rodent models ofHIEcan help elucidate the underlying pathophysiology. We developed a laser speckle imaging (LSI) technique to continuously monitorCBFin six postnatal-day 10 (P10) rats simultaneously before, during, and after unilateral hypoxia-ischemia (HI, ligation of the left carotid artery followed by hypoxia in 8% oxygen). After ligation,CBFto the ligated side fell by 30% compared to the unligated side (P < 0.0001). Hypoxia induced a bilateral 55% reduction inCBF, which was partially restored by resuscitation. Compared to resuscitation in air, resuscitation in 100% oxygen increasedCBFto the ligated side by 45% (P = 0.033). Individual variability inCBFresponse to hypoxia between animals accounted for up to 24% of the variability in hemispheric area loss to the ligated side. In both P10 and P7 models of unilateralHI, resuscitation in 100% oxygen did not affect hemispheric area loss, or hippocampalCA1 pyramidal neuron counts, after 1-week survival. ContinuousCBFmonitoring usingLSIin multiple rodents simultaneously can screen potential treatment modalities that affectCBF, and provide insight into the pathophysiology ofHI.

Acetylation of histones in neocortex and hippocampus of rats exposed to different modes of hypobaric hypoxia: Implications for brain hypoxic injury and tolerance.

Acetylation of nucleosome histones results in relaxation of DNA and its availability for the transcriptional regulators, and is generally associated with the enhancement of gene expression. Although it is well known that activation of a variety of pro-adaptive genes represents a key event in the development of brain hypoxic/ischemic tolerance, the role of epigenetic mechanisms, in particular histone acetylation, in this process is still unexplored. The aim of the present study was to investigate changes in acetylation of histones in vulnerable brain neurons using original well-standardized model of hypobaric hypoxia and preconditioning-induced tolerance of the brain. Using quantitative immunohistochemistry and Western blot, effects of severe injurious hypobaric hypoxia (SH, 180mm Hg, 3h) and neuroprotective preconditioning mode (three episodes of 360mm Hg for 2h spaced at 24h) on the levels of the acetylated proteins and acetylated H3 Lys24 (H3K24ac) in the neocortex and hippocampus of rats were studied. SH caused global repression of the acetylation processes in the neocortex (layers II-III, V) and hippocampus (CA1, CA3) by 3-24h, and this effect was prevented by the preconditioning. Moreover, hypoxic preconditioning remarkably increased the acetylation of H3K24 in response to SH in the brain areas examined. The preconditioning hypoxia without subsequent SH also stimulated acetylation processes in the neocortex and hippocampus. The moderately enhanced expression of the acetylated proteins in the preconditioned rats was maintained for 24h, whereas acetylation of H3K24 was intense but transient, peaked at 3h. The novel data obtained in the present study indicate that large activation of the acetylation processes, in particular acetylation of histones might be essential for the development of brain hypoxic tolerance.

Fluoxetine ameliorates cognitive impairments induced by chronic cerebral hypoperfusion via down-regulation of HCN2 surface expression in the hippocampal CA1 area in rats.

Chronic cerebral hypoperfusion (CCH) causes cognitive impairments and increases the risk of Alzheimer's disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the underlying neurobiological mechanisms are still poorly understood. In this study, we investigated whether fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could play a neuroprotective role against chronic cerebral hypoperfusion injury and to clarify underlying mechanisms of its efficacy. Rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO). Two weeks later, rats were treated with 30 mg/kg fluoxetine (intragastric injection, i.g.) for 6 weeks. Cognitive function was evaluated by Morris water maze (MWM) and novel objects recognition (NOR) test. Long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Western blotting was used to quantify the protein levels. Our results showed that fluoxetine treatment significantly improved the cognitive impairments caused by 2VO, accompanied with a reversion of 2VO-induced inhibitory of LTP. Furthermore, 2VO caused an up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) surface expressions in the hippocampal CA1 area and fluoxetine also effectively recovered the disorder of HCN2 surface expressions, which may be a possible mechanism that fluoxetine treatment ameliorates cognitive impairments in rats with CCH.

Dose-related effects of chronic resveratrol administration on neurogenesis, angiogenesis, and corticosterone secretion are associated with improved spatial memory retention following global cerebral ischemia.

OBJECTIVES: The polyphenol resveratrol has shown regulatory effects on hippocampal neurogenesis, which according to the neurovascular niche hypothesis, is likely to involve stimulation of angiogenesis. In rodents, global cerebral ischemia leads to selective CA1 neuronal damage, spatial memory impairments, lasting changes in corticosterone (CORT) secretion, and increased neurogenesis. This study examined dose-related effects of 21-day RSV treatment on markers associated with neurogenesis (DCX, PSA-NCAM) and angiogenesis (CD31) in the hippocampus at short (7-day) and long-term (85-day) intervals following global ischemia. In parallel, post-ischemic and stress-induced CORT levels and spatial memory in the Morris water maze were determined. METHODS: Five groups of male Wistar rats were included: sham/saline, ischemia/saline, ischemia/1 mg/kg RSV, ischemia/10 mg/kg RSV, and sham/10 mg/kg RSV. Changes in expression of plasticity markers were paralleled by assessment of basal- and stress-induced CORT secretions, and spatial memory performance. RESULTS: Our findings revealed a significant attenuation of ischemia-induced DCX/PSA-NCAM expression in RSV-treated rats, whereas RSV treatment increased angiogenesis in the injured CA1 region. RSV attenuated CORT levels 3 days post-ischemia and a trend toward attenuating CORT secretion in response to 15 minutes restraint stress. Increased swimming latencies in the target quadrant during the MWM probe trial in RSV-treated ischemic rats support beneficial effects of RSV on spatial memory retention. DISCUSSION: Our findings uncover time- and dose-related effects of RSV and global ischemia on the regulation of hippocampal plasticity. Changes in neuro- and angiogenesis are consistent with RSV neuroprotective effects, but appear independent of RSV regulatory effects on corticosterone secretion.

Acupuncture reduced apoptosis and up-regulated BDNF and GDNF expression in hippocampus following hypoxia-ischemia in neonatal rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Acupuncture attenuates neuronal damages following ischemia. AIM OF THE STUDY: The purpose of the present study was to investigate the beneficial effects of acupuncture on hypoxia-ischemia induced brain damages in neonatal rats. MATERIALS AND METHODS: Male postnatal 7 days rats were randomly divided into 3 groups: sham control (sham), hypoxia-ischemia (HI), and HI plus acupuncture treatment (HI+Acu). The rats in HI and HI+Acu groups were submitted to model of neonatal HI, established by occluding the left common carotid artery followed by a 3.5h period of hypoxia (8% O2-92% N2). At 24h after HI, animals were stimulated by acupuncture treatment once a day and the treatment continued during 4 weeks, 5days/week. Behavioral functions, learning and memory ability, and body weight were observed at different time-points after HI. DNA fragmentation assay were performed with TUNEL staining to evaluate apoptosis and expression levels of mitochondrial Bcl-2, mitochondrial Bax, Cleaved caspase 3, Cleaved caspase 9 in the damaged hippocampus were detected by western blotting 28 days following HI. GDNF, BDNF levels in hippocampus were also determined. RESULTS: The results showed that acupuncture significantly promoted growth and development, improved neurobehavioral function, learning and memory ability after 20 days' treatment. Furthermore, we obtained one interesting finding that acupuncture attenuated cellular apoptosis and up-regulated GDNF and BDNF levels in hippocampus. CONCLUSIONS: All of these results suggest that acupuncture as a potential treatment may exert neuroprotective effects via inhibiting cellular apoptosis, increased GDNF and BDNF expression levels in rat hippocampus experiencing HI.

Morphological Analysis of Neurovascular Changes in the Brain in Unilateral Occlusion of the Common Carotid Artery.

Morphological analysis of changes in the brain structures of rats with unilateral occlusion of the common carotid artery showed vascular disorders and neuronal involvement in the anteroparietal cortex and hippocampal CA1 filed on the ipsilateral side.

Nampt/PBEF/visfatin exerts neuroprotective effects against ischemia/reperfusion injury via modulation of Bax/Bcl-2 ratio and prevention of caspase-3 activation.

Nicotinamide phosphoribosyl transferase/pre-B cell colony-enhancing factor/visfatin (Nampt/PBEF/visfatin) is an adipocytokine. By synthesizing nicotinamide adenine dinucleotide (NAD(+)), Nampt/PBEF/visfatin functions to maintain an energy supply that has critical roles in cell survival. Cerebral ischemia leads to energy depletion and eventually neuronal death by apoptosis in specific brain regions specially the hippocampus. However, the role of Nampt/PBEF/visfatin in brain and cerebral ischemia remains to be investigated. This study investigated the role of administration Nampt/PBEF/visfatin in hippocampal CA3 area using a transient global cerebral ischemia model. Both common carotid arteries were occluded for 20 min followed by reperfusion. Saline as a vehicle and Nampt/PBEF/visfatin at a dose of 100 ng were injected intracerebroventricularly (ICV) at the time of cerebral reperfusion. To investigate the underlying mechanisms of Nampt/PBEF/visfatin neuroprotection, levels of expression of apoptosis-related proteins (caspase-3 activation, Bax protein levels, and Bcl-2 protein levels) 96 h after ischemia were determined by immunohistochemical staining. The number of active caspase-3-positive neurons in CA3 was significantly increased in the ischemia group, compared with the sham group (P < 0.001), and treatment with Nampt/PBEF/visfatin significantly reduced the ischemia/reperfusion-induced caspase-3 activation, compared to the ischemia group (P < 0.05). Also, results indicated a significant increase in Bax/Bcl-2 ratio in the ischemia group, compared with the sham group (P < 0.01). However, treatment with Nampt/PBEF/visfatin significantly attenuated the ischemia/reperfusion-induced increase in Bax/Bcl-2 ratio, compared with the ischemia group (P < 0.05). This study has indicated that Nampt/PBEF/visfatin entails neuroprotective effects against ischemia injury when used at the time of cerebral reperfusion. These neuroprotective mechanisms of Nampt/PBEF/visfatin occur through decrease the expression ofproapoptotic proteins (cleaved caspase-3 and Bax) and, on the other hand, increase the expression ofantiapoptotic proteins (Bcl-2). Thus, our findings indicate that Nampt/PBEF/visfatin is a new therapeutic target for cerebral ischemia.

Inhibition of autophagy via activation of PI3K/Akt pathway contributes to the protection of ginsenoside Rb1 against neuronal death caused by ischemic insults.

Lethal autophagy is a pathway leading to neuronal death caused by transient global ischemia. In this study, we examined the effect of Ginsenoside Rb1 (GRb1) on ischemia/reperfusion-induced autophagic neuronal death and investigated the role of PI3K/Akt. Ischemic neuronal death in vitro was induced by using oxygen glucose deprivation (OGD) in SH-SY5Y cells, and transient global ischemia was produced by using two vessels occlusion in rats. Cellular viability of SH-SY5Y cells was assessed by MTT assay, and CA1 neuronal death was evaluated by Hematoxylin-eosin staining. Autophagic vacuoles were detected by using both fluorescent microscopy in combination with acridine orange (AO) and Monodansylcadaverine (MDC) staining and transmission electronic microscopy. Protein levels of LC3II, Beclin1, total Akt and phosphor-Akt at Ser473 were examined by western blotting analysis. GRb1 inhibited both OGD and transient ischemia-induced neuronal death and mitigated OGD-induced autophagic vacuoles in SH-SY5Y cells. By contrast, PI3K inhibitor LY294002 counteracted the protection of GRb1 against neuronal death caused by either OGD or transient ischemia. LY294002 not only mitigated the up-regulated protein level of phosphor Akt at Ser473 caused by GRb1, but also reversed the inhibitory effect of GRb1 on OGD and transient ischemia-induced elevation in protein levels of LC3II and Beclin1.