Ischemia-Induced Changes of PRAS40 and p-PRAS40 Immunoreactivities in the Gerbil Hippocampal CA1 Region After Transient Cerebral Ischemia

Proline-rich Akt substrate of 40-kDa (PRAS40) is one of the important interactive linkers between Akt and mTOR signaling pathways. The increase of PRAS40 is related with the reduction of brain damage induced by cerebral ischemia. In the present study, we investigated time-dependent changes in PRAS40 and phospho-PRAS40 (p-PRAS40) immunoreactivities in the hippocampal CA1 region of the gerbil after 5 min of transient cerebral ischemia. PRAS40 immunoreactivity in the CA1 region was decreased in pyramidal neurons from 12 h after ischemic insult in a time-dependent manner, and, at 5 days post-ischemia, PRAS40 immunoreactivity was newly expressed in astrocytes. p-PRAS40 immunoreactivity in the CA1 pyramidal neurons was hardly found 12 h and apparently detected again 1 and 2 days after ischemic insult. At 5 days post-ischemia, p-PRAS40 immunoreactivity in the CA1 pyramidal neurons was not found. These results indicate that ischemia-induced changes in PRAS40 and p-PRAS40 immunoreactivities in CA1 pyramidal neurons and astrocytes may be closely associated with delayed neuronal death in the hippocampal CA1 region following transient cerebral ischemia.     

Time-Course Changes and New Expressions of MIP-3α and Its Receptor,CCR6, in the Gerbil Hippocampal CA1 Area Following Transient Global Cerebral Ischemia

Macrophage inflammatory protein-3α (MIP-3α) and its sole receptor, CCR6, play pivotal roles in neuroinflammatory processes induced by brain ischemic insults. In this study, we investigated transient ischemia-induced changes in MIP-3α and CCR6 protein expressions in the hippocampal CA1 area following 5 min of transient global cerebral ischemia (tgCI) in gerbils. Both MIP-3α and CCR6 immunoreactivities were very strongly expressed in pyramidal neurons of the CA1 area from 6 h to 1 day after tgCI and were hardly shown 4 days after tgCI. In addition, strong MIP-3α immunoreactivity was newly expressed in astrocytes 6 h after tgCI. These results indicate that tgCI causes apparent changes in MIP-3α and CCR6 expressions in pyramidal neurons and astrocytes in the hippocampal CA1 area and suggest that tgCI-induced changes in MIP-3α and CCR6 expressions might be closely associated with neuroinflammatory processes in brain ischemic regions.     

Decreased Glucokinase Protein Expression in the Aged Gerbil Hippocampus

Glucokinase (GK) and its regulatory protein (GKRP) play roles in glucose utilization as well as glucose-sensing process in the brain. In the present study, we compared GK and GKRP protein expressions in the hippocampus of adult (postnatal month 6) and aged (postnatal month 24) gerbils using immunohistochemistry and western blot analysis. Both GK and GKRP immunoreactivities were observed primarily in the pyramidal cells of the hippocampus proper and in the granule cells of the dentate gyrus of the adult and aged hippocampus. GK, not GKRP, immunoreactivity was apparently decreased in the pyramidal and granule cells of the aged group compared with that in the adult group. In addition, western blot analysis also showed that the GK, not GKRP, protein level was significantly decreased in the aged hippocampus. These results indicate that the decrease of GK may be closely related to the reduction of glucose utilization and uptake, although the ability for regulation of GK is maintained in the aged hippocampus.     

Effects of Transient Cerebral Ischemia on the Expression of DNA Methyltransferase 1 in the Gerbil Hippocampal CA1 Region

DNA methylation is a key epigenetic modification of DNA that is catalyzed by DNA methyltransferases (Dnmt). Increasing evidences suggest that DNA methylation in neurons regulates synaptic plasticity as well as neuronal network activity. In the present study, we investigated the changes in DNA methyltransferases 1 (Dnmt1) immunoreactivity and its protein levels in the gerbil hippocampal CA1 region after 5 min of transient global cerebral ischemia. CA1 pyramidal neurons were well stained with NeuN (a neuron-specific soluble nuclear antigen) antibody in the sham-group, Four days after ischemia–reperfusion (I–R), NeuN-positive (⁺) cells were significantly decreased in the stratum pyramidale (SP) of the CA1 region, and many Fluro-Jade B (a marker for neuronal degeneration)⁺ cells were observed in the SP. Dnmt1 immunoreactivity was well detected in all the layers of the sham-group. Dnmt1 immunoreactivity was hardly detected only in the stratum pyramidale of the CA1 region from 4 days post-ischemia; however, at these times, Dnmt1 immunoreactivity was newly expressed in GABAergic interneurons or astrocytes in the ischemic CA1 region. In addition, the level of Dnmt1 was lowest at 4 days post-ischemia. In brief, both the Dnmt1 immunoreactivity and protein levels were distinctively decreased in the ischemic CA1 region 4 days after transient cerebral ischemia. These results indicate that the decrease of Dnmt1 expression at 4 days post-ischemia may be related to ischemia-induced delayed neuronal death.     

Anti-inflammatory Effect of Tanshinone I in Neuroprotection Against Cerebral Ischemia–Reperfusion Injury in the Gerbil Hippocampus

Tanshinone I (TsI) is an important lipophilic diterpene extracted from Danshen (Radix Salvia miltiorrhizae) and has been used in Asia for the treatment of cerebrovascular diseases such as ischemic stroke. In this study, we examined the neuroprotective effect of TsI against ischemic damage and its neuroprotective mechanism in the gerbil hippocampal CA1 region (CA1) induced by 5 min of transient global cerebral ischemia. Pre-treatment with TsI protected pyramidal neurons from ischemic damage in the stratum pyramidale (SP) of the CA1 after ischemia–reperfusion. The pre-treatment with TsI increased the immunoreactivities and protein levels of anti-inflammatory cytokines [interleukin (IL)-4 and IL-13] in the TsI-treated-sham-operated-groups compared with those in the vehicle-treated-sham-operated-groups; however, the treatment did not increase the immunoreactivities and protein levels of pro-inflammatory cytokines (IL-2 and tumor necrosis factor-α). On the other hand, in the TsI-treated-ischemia-operated-groups, the immunoreactivities and protein levels of all the cytokines were maintained in the SP of the CA1 after transient cerebral ischemia. In addition, we examined that IL-4 injection into the lateral ventricle did not protect pyramidal neurons from ischemic damage. In conclusion, these findings indicate that the pre-treatment with TsI can protect against ischemia-induced neuronal death in the CA1 via the increase or maintenance of endogenous inflammatory cytokines, and exogenous IL-4 does not protect against ischemic damage.     

Increases of Catalase and Glutathione Peroxidase Expressions by Lacosamide Pretreatment Contributes to Neuroprotection Against Experimentally Induced Transient Cerebral Ischemia

Lacosamide is a new antiepileptic drug which is widely used to treat partial-onset seizures. In this study, we examined the neuroprotective effect of lacosamide against transient ischemic damage and expressions of antioxidant enzymes such as Zn-superoxide dismutase (SOD1), Mn-superoxide dismutase (SOD2), catalase (CAT) and glutathione peroxidase (GPX) in the hippocampal cornu ammonis 1 (CA1) region following 5 min of transient global cerebral ischemia in gerbils. We found that pre-treatment with 25 mg/kg lacosamide protected CA1 pyramidal neurons from transient global cerebral ischemic insult using hematoxylin–eosin staining and neuronal nuclear antigen immunohistochemistry. Transient ischemia dramatically changed expressions of SOD1, SOD2 and GPX, not CAT, in the CA1 pyramidal neurons. Lacosamide pre-treatment increased expressions of CAT and GPX, not SOD1 and 2, in the CA1 pyramidal neurons compared with controls, and their expressions induced by lacosamide pre-treatment were maintained after transient cerebral ischemia. In brief, pre-treatment with lacosamide protected hippocampal CA1 pyramidal neurons from ischemic damage induced by transient global cerebral ischemia, and the lacosamide-mediated neuroprotection may be closely related to increases of CAT and GPX expressions by lacosamide pre-treatment.     

Time-course alterations of Toll-like receptor 4 and NF-κB p65, and their co-expression in the gerbil hippocampal CA1 region after transient cerebral ischemia

Innate immune system is very important to modulate the host defense against a large variety of pathogens. Toll-like receptors (TLRs) play a key role in controlling innate immune response. Among TLRs, TLR4 is a specific receptor for lipopolysaccharide and associated with the release of pro-inflammatory cytokines. In the present study, we investigated ischemia-related changes of TLR4 immunoreactivity and its protein level, and nuclear factor κB (NF-κB) p65 immunoreactivity regarding inflammatory responses in the hippocampal CA1 region after 5 min of transient cerebral ischemia to identify the correlation between transient ischemia and inflammation. In the sham-operated group, TLR4 immunoreactivity was easily detected in pyramidal neurons of the hippocampal CA1 region (CA1). TLR4 immunoreactivity in pyramidal neurons was distinctively decreased after ischemia/reperfusion (I/R); instead, based on double immunofluorescence study, TLR4 immunoreactivity was expressed in non-pyramidal neurons and astrocytes from 2 days postischemia. In addition, TLR4 protein level was lowest at 1 day postischemia and highest 4 days after I/R. On the other hand, NF-κB p65 immunoreactivity was not detected in the CA1 of the sham-operated group, and NF-κB p65 immunoreactivity was not observed until 1 day after I/R. However, NF-κB p65 immunoreactivity began to be expressed in astrocytes at 2 days postischemia, and the immunoreactivity was strong 4 days postischemia. Our results indicate that TLR4 and NF-κB p65 immunoreactivity are changed in CA1 pyramidal neurons and newly expressed in astrocytes, not in microglia, in the CA1 region after transient cerebral ischemia.     

Expression of prostaglandin E2 receptor subtypes, EP2 and EP4, in the rat hippocampus after cerebral ischemia and ischemic tolerance

We investigated the distribution and time course of expression of two subtypes of prostaglandin E₂ (PGE₂) receptors, EP2 and EP4, in a rat model of cerebral ischemia and ischemic tolerance. Adult male Sprague-Dawley rats were subjected to either lethal global ischemia (10 min) with or without sublethal ischemic preconditioning (3 min), or ischemia only (3 min). A short 3-min cerebral ischemia and a 3-min ischemia followed by a second lethal ischemia enhanced the expression of EP2 and EP4 receptors in CA1 pyramidal neurons of the hippocampus. In tolerance-acquired CA1 neurons, the immunoreactivities of EP2 and EP4 were upregulated after 4 h and 12 h, respectively. The immunoreactivities were most prominent at 3 days and were sustained for at least 14 days, consistent with results of immunoblotting experiments. However, immunoreactivities for these PGE₂ receptors increased in reactive glial cells in the vulnerable CA1 and hilar regions of rats subjected to lethal ischemia without ischemic preconditioning. Most of the EP2 immunoreactivity occurred in microglial cells and some astrocytes, whereas increased immunoreactivity for EP4 was found only in astrocytes. These data suggest that ischemia and the induction of ischemia tolerance have different regulatory effects on the expression of EP2 and EP4 receptors. Moreover, PGE₂ may exert its unique pathophysiological functions in relation to delayed neuronal death and ischemic tolerance induction in the rat hippocampus via specific PGE₂ receptors.This research was supported by a grant (M103KV010019 04K2201 01930) from the Brain Research Center of the 21st Century Frontier Research Program funded by the Ministry of Science and Technology of the Republic of Korea.     

Origin of Ischemia-Induced Glutamate Efflux in the CA1 Field of the Gerbil Hippocampus: An In Vivo Brain Microdialysis Study

Abstract: In vivo brain microdialysis experiments were performed in the gerbil to evaluate the origin of accumulation of extracellular glutamate under transient ischemia. Microdialysis probes were positioned in the CA1 field of the hippocampus in which proliferation of astrocytes, death of CA1 pyramidal neurons, and damage of presynaptic terminals had been induced by 5-min ischemia 10–14 days before the microdialysis experiment; in the white matter of the cerebral cortex, which contained few neurons, few presynaptic terminals, and many astrocytes; or in the histologically normal CA1 field of the hippocampus, and then 5- or 20-min ischemia was induced. When 5-min ischemia was induced, no significant increase in glutamate content was observed in the CA1 field that showed proliferation of astrocytes, death of CA1 pyramidal neurons, and damage of presynaptic terminals and in the white matter of the cerebral cortex, whereas a significant increase in glutamate (15-fold) was observed in the histologically normal CA1 field. When 20-min ischemia was induced, no significant increase in glutamate content was observed in the CA1 field that showed proliferation of astrocytes, death of CA1 pyramidal neurons, and damage of presynaptic terminals and in the white matter during the first 10 min after the onset of 20-min ischemia, but remarkable ischemia-induced increases in glutamate were observed during the last 10 min of 20-min ischemia in both areas. An excessive increase in glutamate (100-fold) was observed during 20-min ischemia in the normal CA1 field of the hippocampus. When a probe was positioned in the CA1 field of the hippocampus in which presynaptic terminals of Schaffer collaterals and commissural fibers had been eliminated by bilateral kainate injections into the lateral ventricles 4–7 days before the microdialysis experiment and then 5-min ischemia was induced, a significant increase in glutamate was observed during the last half of 5-min ischemia. These results suggest that the efflux of glutamate from astrocytes does not contribute to the large ischemia-induced glutamate accumulation in the CA1 field of the hippocampus during 5-min ischemia but contributes to the ischemia-induced increase in glutamate level during ischemia with a longer duration and that ischemia-induced efflux of glutamate in the CA1 field during 5-min ischemia originates mainly from neuronal elements: presynaptic terminals and postsynaptic neurons.     

Comparison of the Immunoreactivity of Trx2/Prx3 Redox System in the Hippocampal CA1 Region Between the Young and Adult Gerbil Induced by Transient Cerebral Ischemia

In the present study, we compared the immunoreactivities and levels of Trx/prx redox system, thioredoxin 2 (Trx2), thioredoxin reductase 2 (TrxR2) and peroxiredoxin 3 (Prx3), as well as neuronal death in the hippocampal CA1 region between the adult and young gerbil after 5 min of transient cerebral ischemia. At 4 days post-ischemia, pyramidal neurons (about 90%) in the adult stratum pyramidale of the CA1 region showed "delayed neuronal death (DND)"; however, at this time point, few pyramidal neurons showed DND in the young stratum pyramidale. At 7 days post-ischemia, about 56% of pyramidal neurons showed DND in the young stratum pyramidale. The immunoreactivities of all the antioxidants in the young sham-group were similar to those in the adult sham-group. At 4 days post-ischemia, the immunoreactivity of TrxR2, not Trx2 and Prx3 in the adult ischemia-group was dramatically decreased in CA1 pyramidal neurons. At this time point, the immunoreactivities of all the antioxidants in the young ischemia-group were apparently increased compared to the adult ischemia-group. From 7 days pots-ischemia, non-pyramidal cells showed the immunoreactivities of all the antioxidants in the ischemic CA1 region; however, in the young ischemia-groups, the immunoreactivities were much lower than those in the adult ischemia-groups. In brief, our results showed that the immunoreactivities of Trx2, TrxR2 and Prx3 were dramatically increased in CA1 pyramidal neurons of the young ischemia-groups at 4 days post-ischemia compared to those in the adult ischemia-groups induced by transient cerebral ischemia.     

Na+/HCO3- cotransporter immunoreactivity changes in neurons and expresses in astrocytes in the gerbil hippocampal CA1 region after ischemia/reperfusion

The maintenance of intracellular pH is important in neuronal function. Na⁺/HCO₃ ⁻ cotransporter (NBC), a bicarbonate-dependent acid–base transport protein, may contribute to cellular acid–base homeostasis in pathophysiological processes. We examined the alterations of NBC immunoreactivity and its protein levels in the hippocampal CA1 region after transient cerebral ischemia in gerbils. In the sham-operated group, moderate NBC immunoreactivity was detected in CA1 pyramidal neurons, and, 12 h after I/R, the immunoreactivity in the pyramidal neurons was markedly increased over controls. Three days after I/R, NBC immunoreactivity nearly disappeared in the CA1 pyramidal neurons. However, NBC immunoreactivity was detected in the non-pyramidal neurons of the ischemic CA1 region at 3 days after I/R. From double immunofluorescence study with glial markers, NBC immunoreactivity was detected in astrocytes, not in microglia, at 4 days after I/R. NBC protein level in the CA1 region was significantly increased at 12 h post-ischemia and significantly decreased at 2 days post-ischemia. Thereafter, NBC protein level was again increased and returned to the level of the sham-operated group at 4 days post-ischemia. On the other hand, treatment with 4,4′-diisothiocyanatostilbene-2,2′-disulfonate (DIDS), an inorganic anion exchanger blocker including Cl-bicarbonate exchanger, protected CA1 pyramidal neurons from I/R injury at 4 days post-ischemia. These results indicate that changes in NBC expressions may play an important role in neuronal damage and astrocytosis induced by transient cerebral ischemia.     

Neuroprotective effects of valproic acid following transient global ischemia in rats

AimsA growing number of studies demonstrate that valproic acid (VPA), an anti-convulsant and mood-stabilizing drug, is neuroprotective against various insults. This study investigated whether treatment of ischemic stroke with VPA ameliorated hippocampal cell death and cognitive deficits. Possible mechanisms of action were also investigated.Main methodsGlobal cerebral ischemia was induced to mimic ischemia/reperfusion (I/R) damage. The pyramidal cells within the CA1 field were stained with cresyl violet. Cognitive ability was measured 7 days after I/R using a Morris water maze. The anti-inflammatory effects of VPA on microglia were also investigated by immunohistochemistry. Pro-inflammatory cytokine production was determined using enzyme-linked immunosorbent assays (ELISA). Western blot analysis was performed to determine the levels of acetylated H3, H4 and heat shock protein 70 (HSP70) in extracts from the ischemic hippocampus.Key findingsVPA significantly increased the density of neurons that survived in the CA1 region of the hippocampus on the 7th day after transient global ischemia. VPA ameliorated severe deficiencies in spatial cognitive performance induced by transient global ischemia. Post-insult treatment with VPA also dramatically suppressed the activation of microglia but not astrocytes, reduced the number of microglia, and inhibited other inflammatory markers in the ischemic brain. VPA treatment resulted in a significant increase in levels of acetylated histones H3 and H4 as well as HSP70 in the hippocampus.SignificanceOur results indicated that VPA protected against hippocampal cell loss and cognitive deficits. Treatment with VPA following cerebral ischemia probably involves multiple mechanisms of action, including inhibition of ischemia-induced cerebral inflammation, inhibition of histone deacetylase (HDAC) and induction of HSP.     

Ischemia induced changes in expression of the astrocyte glutamate transporter GLT1 in hippocampus of the rat

Changes in cellular uptake of glutamate following transient cerebral ischemia is of possible importance to ischemia induced cell death. In the present study, we employed in situ hybridization and immunohistochemistry to investigate the influence of cerebral ischemia on expression of mRNA and protein of the astrocyte glutamate transporter GLT1, and of glial fibrillary acidic protein. Different subfields of CA1 and CA3 of the rat hippocampus were studied at various time-points after ischemia (days 1, 2, 4, and 21). In CA1, GLT1-mRNA was decreased at all time-points after ischemia except from day 2, whereas in CA3, decreases were seen only on day 1. Expression of GLT1-protein in CA1 was unchanged during the initial days after ischemia, but decreased markedly from day 2 to 4. In CA3, GLT1-protein increased progressively throughout the observation period after ischemia. Following the degeneration of CA1 pyramidal cells, a positive correlation between the number of CA1 pyramidal cells and expression of either GLT1-mRNA or -protein was evident selectively in CA1. Increases in expression of mRNA and protein of glial fibrillary acidic protein were present from day 2, most notable in CA1. The present data provide evidence that expression of GLT1 in CA1 of the hippocampus is not decreased persistently before the degeneration of CA1 pyramidal cells, but is downregulated in response to loss of these neurons. Since the reduction in GLT1 expression evolved concomitantly with the degeneration of CA1 pyramidal cells, it may contribute to the severity of CA1 pyramidal cell loss. A progressive postischemic increase in GLT1 expression in CA3 may be linked to the resistance of CA3 neurons to ischemic cell damage.     

Comparison of Trophic Factors Changes in the Hippocampal CA1 Region Between the Young and Adult Gerbil Induced by Transient Cerebral Ischemia

In the present study, we investigated neuronal death/damage in the gerbil hippocampal CA1 region (CA1) and compared changes in some trophic factors, such as brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and vascular endothelial growth factor (VEGF), in the CA1 between the adult and young gerbils after 5?min of transient cerebral ischemia. Most of pyramidal neurons (89?%) were damaged 4?days after ischemia?Creperfusion (I?CR) in the adult; however, in the young, about 59?% of pyramidal neurons were damaged 7?days after I?CR. The immunoreactivity and levels of BDNF and VEGF, not GDNF, in the CA1 of the normal young were lower than those in the normal adult. Four days after I?CR in the adult group, the immunoreactivity and levels of BDNF and VEGF were distinctively decreased, and the immunoreactivity and level of GDNF were increased. However, in the young group, all of their immunoreactivities and levels were much higher than those in the normal young group. From 7?days after I?CR, all the immunoreactivities and levels were apparently decreased compared to those of the normal adult and young. In brief, we confirmed our recent finding: more delayed and less neuronal death occurred in the young following I?CR, and we newly found that the immunoreactivities of trophic factors, such as BDNF, GDNF, and VEGF, in the stratum pyramidale of the CA1 in the young gerbil were much higher than those in the adult gerbil 4?days after transient cerebral ischemia.     

Microglia with an Endothelin ETB Receptor Aggregate in Rat Hippocampus CA1 Subfields Following Transient Forebrain Ischemia

Abstract: We examined endothelin (ET) receptors in the hippocampus CA1 subfields of stroke-prone spontaneously hypertensive rats subjected to a 10-min bilateral carotid occlusion and reperfusion. When delayed neuronal death had occurred in the pyramidal cell layer at 7 days after transient forebrain ischemia, the quantitative receptor autoradiographic method we used revealed a dramatic increase in number of ¹²⁵I-ET-1 binding sites in the hippocampus CA1 subfields. The highest number of de novo binding sites appeared in the area corresponding anatomically to the pyramidal cell layer with neuronal death. These binding sites were characteristically the ET_B receptor. The de novo ¹²⁵I-ET-1 binding was mainly present on microglia aggregating with a high density in the damaged pyramidal cell layer. As ET-1- and ET-3-like immunoreactivities were highly expressed within astrocytes in damaged neural tissue, the possibility that microglia with the ET_B receptor are activated to participate in the pathophysiology of ischemia-related neural tissue damage by astrocytic ET-1 and ET-3 produced in response to transient forebrain ischemia would have to be considered.     

Isoform-Specific Redistribution of Calcineurin Aα and Aβ in the Hippocampal CA1 Region of Gerbils After Transient Ischemia

Abstract: To investigate isoform-specific roles of Ca²⁺/calmodulin-dependent phosphatase [calcineurin (CaN)] in ischemia-induced cell death, we raised antibodies specific to CaN Aα and CaN Aβ and localized the CaN isoforms in the hippocampal CA1 region of Mongolian gerbils subjected to a 5-min occlusion of carotid arteries. In the nonischemic gerbil, immunoreactions of both isoforms were highly enriched in CA1 regions, especially in the cytoplasm and apical dendrites of CA1 pyramidal neurons. At 4–7 days after the induced ischemia, immunoreactivities of the CaN Aα isoform in CA1 pyramidal cells were markedly reduced, whereas they were enhanced in the CA1 radiatum and oriens layers. In contrast, CaN Aβ immunoreactivities were reduced in all layers of the ischemic CA1 region, whereas they were enhanced in activated astrocytes, colocalizing with glial fibrillary acidic protein. These findings suggest that up-regulation of CaN Aα in afferent fibers in CA1 and up-regulation of CaN Aβ in reactive astrocytes may be involved in neuronal reorganization after ischemic injury.     

Comparison of Glial Activation in the Hippocampal CA1 Region Between The Young and Adult Gerbils After Transient Cerebral Ischemia

It has been reported that young animals are less vulnerable to brain ischemia. In the present study, we compared gliosis in the hippocampal CA1 region of the young gerbil with those in the adult gerbil induced by 5?min of transient cerebral ischemia by immunohistochemistry and western blot for glial cells. We used male gerbils of postnatal month 1 (PM 1) as the young and PM 6 as the adult. Neuronal death in CA1 pyramidal neurons in the adult gerbil occurred at 4?days posti-schemia; the neuronal death in the young gerbil occurred at 7?days post-ischemia. The findings of glial changes in the young gerbil after ischemic damage were distinctively different from those in the adult gerbil. Glial fibrillary acidic protein-immunoreactive astrocytes, ionized calcium-binding adapter molecule (Iba-1), and isolectin B4-immunoreactive microglia in the ischemic CA1 region were activated much later in the young gerbil than in the adult gerbil. In brief, very less gliosis occurred in the hippocampal CA1 region of the young gerbil than in the adult gerbil after transient cerebral ischemia.     

Temporal Profiles of Nerve Growth Factor β-Subunit Level in Rat Brain Regions After Transient Ischemia

To determine the role of nerve growth factor (NGF) in ischemic brain damage, we measured the temporal and regional changes in the level of NGF in the hippocampal subfields, the cerebral cortex, the striatum, and the septum at 1, 2, 7, and 30 days after transient forebrain ischemia using a highly sensitive sandwich-type enzyme immunoassay system for the beta-subunit of mouse 7S NGF (beta-NGF). We also analyzed glial fibrillary acidic protein immunoreactivity in the hippocampus to ascertain the contribution of reactive astrocytes to NGF production after an ischemic insult. In the CA1 subfield of the hippocampus, the level of beta-NGF decreased slightly 2 days after ischemia (not significant), at which time CA1 pyramidal cell loss began to occur, and increased by 40% 30 days after ischemia (p less than 0.05). A marked increase in glial fibrillary acidic protein-positive astrocytes in the CA1 subfield 2-30 days after ischemia suggests that the reactive astrocytes participated in a gradual increase in the level of beta-NGF after recirculation. The level of beta-NGF in the dentate gyrus decreased transiently 2 days (p less than 0.05) and 7 days (p less than 0.01) after ischemia, followed by recovery to the level of control animals 30 days after ischemia. The level of beta-NGF in the septum gradually decreased 7 days (-27%, p less than 0.05) and 30 days (-43%, p less than 0.01) after ischemia. The levels of beta-NGF in the cerebral cortex and striatum remained unaltered throughout the observation period.(ABSTRACT TRUNCATED AT 250 WORDS)