缺血预处理后海马CA1区反应性星形胶质细胞增生与迟发性神经元缺血耐受性的关系

目的 探讨缺血预处理后海马CA1区反应性星形胶质细胞增生与迟发性神经元缺血耐受性的关系。方法 实验动物被随机分为手术组、缺血组、预缺血组、预缺血后再缺血组。阴断沙土鼠双侧颈总动脉造成前脑缺血模型。采用细胞特异性抗原胶质纤维酸性蛋白（GFAP）免疫组化法标记星形胶质细胞。结果 预缺血后1－7天,海马CA1区GFAP阳性的星形胶质细胞数轻度增加,至28天时增生非常显著（P＜0．01）。预缺血后1－7天再缺血,海马CA1区存活正常神经元数逐渐下降,预缺血后28天再缺血又显著增加（P＜0．01）。结论 缺血预处理后,神经元可出现迟发性缺血耐受,反应性星形胶质细胞增生可能起了重要作用。     

大鼠脑缺血再灌注后星形胶质细胞反应性变化差异与海马CA1区的迟发性神经元死亡

BACKGROUND： Blood supply to the hippocampus is not provided by the middle cerebral artery. However, previous studies have shown that delayed neuronal death in the hippocampus may occur following focal cerebral ischemia induced by middle cerebral artery occlusion.
OBJECTIVE： To observe the relationship between reactive changes in hippocampal astrocytes and delayed neuronal death in the hippocampal CA1 region following middle cerebral artery occlusion.
DESIGN, TIME AND SETTING： The immunohistochemical, randomized, controlled animal study was performed at the Laboratory of Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, from July to November 2007.
MATERIALS： Rabbit anti-glial fibrillary acidic protein （GFAP） （Neomarkers, USA）, goat anti-rabbit IgG （Sigma, USA） and ApoAlert apoptosis detection kit （Biosciences Clontech, USA） were used in this study. METHODS： A total of 42 healthy adult male Wistar rats, aged 3–5 months, were randomly divided into a sham operation group （n = 6） and a cerebral ischemia/reperfusion group （n = 36）. In the cerebral ischemia/reperfusion group, cerebral ischemia/reperfusion models were created by middle cerebral artery occlusion. In the sham operation group, the thread was only inserted into the initial region of the internal carotid artery, and middle cerebral artery occlusion was not induced. Rats in the cerebral ischemia/reperfusion group were assigned to a delayed neuronal death （＋） subgroup and a delayed neuronal death （–） subgroup, according to the occurrence of delayed neuronal death in the ischemic side of the hippocampal CA1 region following cerebral ischemia.
MAIN OUTCOME MEASURES： Delayed neuronal death in the hippocampal CA1 region was measured by Nissl staining. GFAP expression and delayed neuronal death changes were measured in the rat hippocampal CA1 region at the ischemic hemisphere by double staining for GFAP and TUNEL.
RESULTS： After 3 days of ischemia/reperfusion, astrocytes with abnormal morphology were detected in the rat hippocampal CA1 region in the delayed neuronal death （＋） subgroup. No significant difference in GFAP expression was found in the rat hippocampal CA1 region at the ischemic hemisphere in the sham operation group, delayed neuronal death （＋） subgroup and delayed neuronal death （–） subgroup （P 〉 0.05）. After 7 days of ischemia/reperfusion, many GFAP-positive cells, which possessed a large cell body and an increased number of processes, were activated in the rat hippocampal CA1 region at the ischemic hemisphere. GFAP expression in the hippocampal CA1 region was greater in the delayed neuronal death （＋） subgroup and delayed neuronal death （–） subgroup compared with the sham operation group （P 〈 0.01）. Moreover, GFAP expression was significantly greater in the delayed neuronal death （–） subgroup than in the delayed neuronal death （＋） subgroup （P 〈 0.01）. After 30 days of ischemia/reperfusion, GFAP-positive cells were present in scar-like structures in the rat hippocampal CA1 region at the ischemic hemisphere. GFAP expression was significantly greater in the delayed neuronal death （＋） subgroup and delayed neuronal death （–） subgroup compared with the sham operation group （P 〈 0.05）. GFAP expression was significantly lower in the delayed neuronal death （–） subgroup than in the delayed neuronal death （＋） subgroup （P 〈 0.05）. The delayed neuronal death rates were 42% （5/12）, 33% （4/12） and 33% （4/12） at 3, 7 and 30 days, respectively, followingischemia/reperfusion. No significant differences were detected at various time points （χ2 = 0.341, P 〉 0.05）.
CONCLUSION： The activation of astrocytes was poor in the hippocampal CA1 region during the early stages of ischemia, which is an important reason for delayed neuronal death. Glial scar formation aggravated delayed neuronal death during the advanced ischemic stage.     

Expression of neuron specific phosphatase, striatal enriched phosphatase (STEP) in reactive astrocytes after transient forebrain ischemia

We studied the distribution and change of striatal enriched phosphatase (STEP) in the gerbil hippocampus after transient forebrain ischemia. STEP was expressed in the perikarya and in neuronal processes; it was not detected in non-neuronal cells of control animals. After 5-min forebrain ischemia, STEP immunoreactivity (STEP-IR) was preserved for 2 days; it disappeared 4 and more days after ischemia with completion of delayed neuronal death (DND) in the CA1 subfield. Furthermore, only in the CA1 after ischemia, STEP was expressed in reactive astrocytes for 4 to 28 days, showing different patterns of glial fibrillary acidic protein (GFAP)-positive reactive astrocytes. After non-or less-than lethal ischemia, STEP expression in reactive astrocytes corresponded with the degree of neuronal degeneration. Immunoblot analysis of the CA1 subfield revealed the expression of three isoforms, STEP45, -56 and -61; their expression patterns changed with time after ischemia. These data suggest that neuronal STEP is preserved until cell degeneration after ischemia and that STEP is expressed in reactive astrocytes only after lethal ischemia, with different expression patterns for its isoforms. Of STEP45, -56 and -61, STEP61 was the most strongly expressed in the reactive astrocytes; both STEP45 and -61 were expressed in neurons and the expression of STEP56 was weak. STEP may play an important role not only in neurons but also in reactive astrocytes after ischemia, depending on neuronal degeneration.     

Adenosine treatment delays postischemic hippocampal CA1 loss after cardiac arrest and resuscitation in rats

Resuscitation from cardiac arrest results in reperfusion injury that leads to increased postresuscitation mortality and delayed neuronal death. One of the many consequences of resuscitation from cardiac arrest is a derangement of energy metabolism and the loss of adenylates, impairing the tissue's ability to regain proper energy balance. In this study, we investigated the effects of adenosine (ADO) on the recovery of the brain from 12 min of ischemia using a rat model of cardiac arrest and resuscitation. Compared to the untreated group, treatment with adenosine (7.2 mg/kg) initiated immediately after resuscitation increased the proportion of rats surviving to 4 days and significantly delayed hippocampal CA1 neuronal loss. Brain blood flow was increased significantly in the adenosine-treated rats 1 h after cardiac arrest and resuscitation. Adenosine-treated rats exhibited less edema in cortex, brainstem and hippocampus during the first 48 h of recovery. Adenosine treatment significantly lowered brain temperature during recovery, and a part of the neuroprotective effects of adenosine treatment could be ascribed to adenosine-induced hypothermia. With this dose, adenosine may have a delayed transient effect on the restoration of the adenylate pool (AXP = ATP + ADP + AMP) 24 h after cardiac arrest and resuscitation. Our findings suggested that improved postischemic brain blood flow and ADO-induced hypothermia, rather than adenylate supplementation, may be the two major contributors to the neuroprotective effects of adenosine following cardiac arrest and resuscitation. Although adenosine did not prevent eventual CA1 neuronal loss in the long term, it did delay neuronal loss and promoted long-term survival. Thus, adenosine or specific agonists of adenosine receptors should be evaluated as adjuncts to broaden the window of opportunity in the treatment of the reperfusion injury following cardiac arrest and resuscitation.     

Late expression of Na+/H+ exchanger 1 (NHE1) and neuroprotective effects of NHE inhibitor in the gerbil hippocampal CA1 region induced by transient ischemia

Although acidosis may be involved in neuronal death, the participation of Na⁺/H⁺ exchanger (NHE) in delayed neuronal death in the hippocampal CA1 region induced by transient forebrain ischemia has not been well established. In the present study, we investigated the chronological alterations of NHE1 in the hippocampal CA1 region using a gerbil model after ischemia/reperfusion. In the sham-operated group, NHE1 immunoreactivity was weakly detected in the CA1 region. Two and 3 days after ischemia/reperfusion, NHE1 immunoreactivity was observed in glial components, not in neurons, in the CA1 region. Four days after ischemia/reperfusion, NHE1 immunoreactivity was markedly increased in CA1 pyramidal neurons as well as glial cells. These glial cells were identified as astrocytes based on double immunofluorescence staining. Western blot analysis also showed that NHE protein level in the CA1 region began to increase 2 days after ischemia/reperfusion. The treatment of 10 mg/kg 5-(N-ethyl-N-isopropyl) amiloride, a NHE inhibitor, significantly reduced the ischemia-induced hyperactivity 1day after ischemia/reperfusion. In addition, NHE inhibitor potently protected CA1 pyramidal neurons from ischemic damage, and NHE inhibitor attenuated the activation of astrocytes and microglia in the ischemic CA1 region. In addition, NHE inhibitor treatment blocked Na⁺/Ca²⁺ exchanger 1 immunoreactivity in the CA1 region after transient forebrain ischemia. These results suggest that NHE1 may play a role in the delayed death, and the treatment with NHE inhibitor protects neurons from ischemic damage.     

Morphological transformations of cells immunopositive for GFAP, TrkA or p75 in the CA1 hippocampal area following transient global ischemia in the rat. A quantitative study

Transient global ischemia induces intensive neuronal degeneration in the hippocampal CA1 pyramidal layer, accompanied by reactive transformation of glial cells. Previously, we have shown using the double immunostaining method that the NGF receptors (NGFR) p75 and TrkA are expressed mainly on subpopulations of GFAP+ astrocytes, and this expression increases progressively after ischemia. In the presented study, we analyzed quantitatively the morphological transformations of cells immunopositive for GFAP or NGF receptors in the stratum radiatum of the CA1 hippocampal area in different survival periods after ischemia, evoked by 10-min cardiac arrest in adult rats. In control brains, NGF receptors were expressed only on small cells with poorly ramified processes. After ischemia, the NGFR+ cells increased in size and morphological complexity (measured using fractal analysis). However, even 2 weeks after ischemia these cells did not reach the size and value of the fractal dimension typical of the largest GFAP+ astrocytes. Moreover, the reaction of NGFR+ cells was significantly delayed in comparison with the total astrocyte population. The obtained results suggest that NGF receptors are expressed mainly by immature astrocytes and ischemia induces the maturation of these cells.     

Expresgions of nerve growth factor and p75 low affinity receptor after transient forebrain ischemia in gerbil hippocampal CA1 neurons

Expressions of nerve growth factor (NGF) and low affinity p75 NGF receptor (p75 NGFR) in gerbil hippocampal neurons after 3.5-min transient forebrain ischemia were studied. Most hippocampal CAI neurons were lost (neuronal density = 44 ± 12/mm) at 7 days after recirculation, while no cell death was found in the sham-control neurons (220 ± 27/min). NGF immunoreactivity was normally present in the sham-control hippocampal neurons. However, it decreased in hippocampal CAI neurons, and slightly decreased in the neurons of CA3 and dentate gyrus areas from 3 hr after recirculation. By 7 days, NGF immunoreactivity returned almost completely to the sham-control level in the CA3 and dentate gyrus neurons but decreased markedly in the CAI neurons. In contrast, p75 NGFR immunoreactivity was scarcely present in the sham-control hippocampal neurons but was induced from 1 hr after recirculation in the CAI and CA3 neurons and from 3 hr in the dentate gyrus. At 7 days, p75 NGFR immunoreactivity was expressed greatly in the surviving CAI neurons and the reactive astrocytes but was not seen in the other hippocampal neurons. The markedly decreased NGF and greatly induced p75 NGFR immunoreactivity found in the CAI neurons after transient forebrain ischemia suggests that NGF and p75 NGFR may be involved in the mechanism of delayed neuronal death. © 1995 Wiley-Liss, Inc.     

A reversible type of neuronal injury following ischemia in the gerbil hippocampus

The Mongolian gerbil is known to develop delayed neuronal death in the hippocampus following brief forebrain ischemia (Brain Res 239: 57-69, 1982). The effect of pentobarbital on this slow process of neuronal damage was examined. Immediately following 5 min of bilateral carotid occlusion, pentobarbital (10, 20, or 40 mg/kg) was injected. The control animals received saline injection. Seven days following ischemic insult, animals were perfusion-fixed and the neuronal density in the hippocampal CA1 subfield was counted. Most of the neurons in the CA1 sector survived ischemic insult when pentobarbital was given, whereas most of control group neurons were lost without the treatment. The average neuronal density of 20 mg/kg group was 168.2 +/- 12.3 (SEM) per 1 mm linear length of the CA1 subfield. The density in 40 mg/kg group was 181.1 +/- 14.9. The neuronal density in the whole control group was 34.3 +/- 5.1. The density of unoperated normal gerbils was 212.3 +/- 3.9. This result indicates that the neuronal damage of "delayed neuronal death" is reversible. On the other hand, when pentobarbital was injected 1 hr following ischemia, it showed no effect. The cell change in the CA1 sector, reversible at the initial stage, seems to rapidly become irreversible, while neurons still remain intact morphologically.     

Treatable ischemic neuronal damage in the gerbil hippocampus

The Mongolian gerbil is known to develop delayed neuronal death in the hippocampus following brief forebrain ischemia (Brain Res 239: 57-69). Morphological, biochemical, or electrophysiological studies on this neuronal injury have shown that neurons still retain potential reversibility at the earlier period of alteration. To examine this possibility, immediately following 5 min of ischemia in the gerbil, pentobarbital, diazepam, or nizofenone was injected. Seven days following ischemic insult, animals were perfusion fixed and neuronal density in the hippocampal CA1 subfield was counted. Most of the neurons in the CA1 sector survived ischemic insult when a drug was given, whereas most of them were lost without the treatment. The average neuronal density of treated groups showed a statistically significant (p less than 0.01) persistence compared with that of control group. The effective dosage of the drugs were 20-40 mg/kg in pentobarbital, 10-20 mg/kg in diazepam, and 12.5-25 mg/kg in nizofenone. On the other hand, when pentobarbital was injected 1 hr following ischemia, while neurons still remain intact morphologically, it showed no effect. This result indicates that the neuronal damage of "delayed neuronal death" type is reversible if treatment is instituted at an early period of cell change.     

Delayed neuronal death and delayed neuronal recovery in the human brain following global ischemia

Summary The understanding of delayed hippocampal death as a therapeutic window for post-ischemic treatment of the brain has led to numerous investigations focusing upon underlying cellular mechanisms and pharmacological potentials in gerbils and rats. Nevertheless, studies on the occurrence of delayed neuronal death in the human brain have been singular and dealt with only small files of patients. To complement these limited data, in the present study 26 adult patients with a history of a single cardiac arrest were included. Following successful resuscitation, individual survival ranged from less than 1 h to 186 days ( = 11 days). The severity of the resultant ischemic injury in hippocampus CA1, among Purkinje cells, or in frontal neocortex, respectively, was quantified by direct counting of necrotic neurons. Additionally, hippocampal specimens were immunostained for neuron-specific enolase. The data obtained demonstrate the occurrence of delayed neuronal death in human hippocampus and, in a minor form, in cerebellar Purkinje cells. This is in contrasts to the immediate manifestation of ischemic neuronal necrosis in the neocortex. Unlike previous findings in experimental animals and in humans, the delay of CA1 cell death could be defined as lasting about 7 days following cardiac arrest. Moreover, the immunohistochemical results indicate delayed neuronal recovery in CA1, which in the time course reciprocally corresponds to delayed manifestation of hippocampal neuronal death. Interpretation of the results must consider the lack of information about the exact individual duration of cardiac arrest and resuscitation, as well as missing data concerning pre-ischemic physiological variables.     

Sexually Dimorphic Response of TRPM2 Inhibition Following Cardiac Arrest-Induced Global Cerebral Ischemia in Mice

Transient global cerebral ischemia due to cardiac arrest followed by resuscitation (CA/CPR) causes significant neurological damage in vulnerable neuron populations within the brain, such as hippocampal CA1 neurons. In recent years, we have implicated the transient receptor potential M2 (TRPM2) channel as a mediator of ischemic injury to neurons. We previously demonstrated that genetic and pharmacological strategies that reduce TRPM2 function preferentially protect male neurons in vitro and reduce infarct volume following experimental stroke. Due to the narrow therapeutic window for intervention following ischemic stroke, it is important to assess the role of TRPM2 in other models of cerebral ischemia. Therefore, this study utilized a modified mouse model of CA/CPR to mimic more accurately the clinical condition by maintaining body and head temperatures near the physiological range throughout. Here, we report that inhibition of TRPM2 activity with clotrimazole reduces hippocampal CA1 neuronal injury when administered 30 min after resuscitation from cardiac arrest. Consistent with our previous observations, neuroprotection was observed in male mice and no effect on injury was observed in the female. These findings provide further evidence for TRPM2 as a target for protection against cerebral ischemia in the male brain.     

Calpain inhibitor entrapped in liposome rescues ischemic neuronal damage

Transient forebrain ischemia induces activation of calpain and proteolysis of a neuronal cytoskeleton, fodrin, in gerbil hippocampus. This phenomenon precedes delayed neuronal death in hippocampal CA1 neurons. We examined effects of a calpain inhibitor on delayed neuronal death after transient forebrain ischemia. In gerbils, a selective calpain inhibitor entrapped in liposome was given transvenously and 30 min later, 5-min forebrain ischemia was produced by occlusion of both common carotid arteries. On day 7, CA1 neuronal damage was examined in the hippocampal slices stained with cresyl violet. Calpain-induced proteolysis of fodrin was also examined by immunohistochemistry and immunoblot. Additionally, to assure entrapment of the inhibitor by CA1 neurons, the inhibitor-liposome complex was labeled with FITC and given to gerbils. Fluorescence in the hippocampal slices was examined by confocal laser scanning microscope. Selective CA1 neuronal damage induced by forebrain ischemia was prevented by administration of the inhibitor in a dose-dependent manner. Calpain-induced proteolysis of fodrin was also extinguished by the calpain inhibitor in a dose-dependent manner. Bright fluorescence of the FITC-labeled inhibitor was observed in the CA1 neurons. The data show an important role of calpain in the development of the ischemic delayed neuronal death. Calpain seems to produce neuronal damage by degrading neuronal cytoskeleton. Our data also show a palliative effect of the calpain inhibitor on the neurotoxic damage, which offers a new and potent treatment of transient forebrain cerebral ischemia.     

Hypothyroid state does not protect but delays neuronal death in the hippocampal CA1 region following transient cerebral ischemia: Focus on oxidative stress and gliosis

We investigated protective effects of hypothyroidism on delayed neuronal death, gliosis, lipid peroxidation and Cu,Zn‐superoxide dismutase (SOD1) in the gerbil hippocampal CA1 region (CA1) after 5 min of transient cerebral ischemia. The hypothyroidism was induced by 0.025% methimazole treatment. Free triiodothyronine and thyroxine levels were markedly decreased in the hypothyroid group. Four days after ischemia/reperfusion, only a few NeuN‐immunoreactive (+) neurons were detected in the CA1 of euthyroid‐ischemia (eu‐ischemia) group; however, at this time point, the number of NeuN⁺ neurons was significantly higher in the hypothyroid‐ischemia (hypo‐ischemia) group than in the eu‐ischemia group. At 5 days postischemia, NeuN⁺ neurons were significantly decreased in the hypo‐ischemia group: The number of NeuN⁺ neurons in this group was similar to that in the eu‐ischemia group. Activations of GFAP⁺ astrocytes and Iba‐1⁺ microglia in the CA1 were higher in the eu‐ischemia group 3 and 4 days after ischemia/reperfusion. At 5 days postischemia, the activations of both the glial cells in the CA1 were similar between the two groups. 4‐Hydroxy‐2‐nonenal (HNE), a marker for lipid peroxidation, immunoreactivity in the eu‐ischemia group was higher than in the hypo‐ischemia group; at 5 days postischemia, the immunoreactivity was similar between the two groups. In contrast, SOD1 level was lower in the CA1 of the eu‐ischemia group. These results suggest that hypothyroid state does not protect against delayed neuronal death but only delays the neuronal death in the hippocampal CA1 region after transient cerebral ischemia by reducing lipid peroxidation and increasing SOD1. © 2010 Wiley‐Liss, Inc.     

Electron microscopic investigation of rat brain after brief cardiac arrest

Rats were submitted to 10-min cardiac arrest, followed by resuscitation and survival for 1 day, 3 days or 1 week. Five regions of interest (CA1 and CA3 sector of hippocampus, dentate gyrus, reticular nucleus of thalamus and parietal cortex) where studied by light and electron microscopy at each of the survival times, and compared with non-ischemic control rats. Cell counts revealed delayed neuronal loss of about 30% after 3 days in both CA1 and CA3 sectors. Ischemic cell changes consisting of cytoplasmic condensation and nuclear pyknosis appeared in these regions on day 7 and --to a lesser degree-- also affected dentate gyrus, the reticular nucleus of thalamus and cerebral cortex. Ultrastructural alterations were evaluated using an ultrastructural injury catalogue. In all brain regions similar, although quantitatively differently expressed, changes occurred except ribosomal disaggregation, which was restricted to neurons of hippocampal CA1 sector on the first day after cardiac arrest. Progressive alterations included swelling of mitochondria and endoplasmic reticulum, which was most pronounced in CA1 and CA3 sectors of hippocampus, as well as chromatin aggregation and alterations of neuronal volume, which affected mainly the granule cells of dentate gyrus. Other alterations, such as osmiophilic inclusions or the formation of nuclear pore complexes, were transient with a maximum on the first day after cardiac arrest. Treatment with the free-radical scavenger alpha-phenyl-N-tert-butyl nitrone (PBN) suppressed the formation of nuclear pores but otherwise did not markedly change the morphological outcome. In comparison to previous studies of global brain ischemia induced by arterial inflow occlusion of the same duration, the present data demonstrate remarkable preservation of tissue integrity in CA1 sector but also distinct changes in brain regions considered to be resistant to ischemic injury. Morphological alterations of brain after cardiac arrest do not follow the established pattern of selective vulnerability.     

Global cerebral ischemia due to cardiocirculatory arrest in mice causes neuronal degeneration and early induction of transcription factor genes in the hippocampus

To analyze the role of specific genes and proteins in neuronal signaling cascades following global cerebral ischemia, it would be useful to have a reproducible model of global cerebral ischemia in mice that potentially allows the investigation of mice with specific genomic mutations. We first report on the development of a model of reversible cardiocirculatory arrest in mice and the consequences of such an insult to neuronal degeneration and expression of immediate early genes (IEG) in the hippocampus. Cardiocirculatory arrest of 5 min duration was induced via ventricular fibrillation in mechanically ventilated NMRI mice. After successful cardiopulmonary resuscitation (CPR), animals were allowed to reperfuse spontaneously for 3 h (n=7) and 7 days (n=7). TUNEL staining revealed a selective degeneration of a subset of neurons in the hippocampal CA1 sector at 7 days. About 30% of all TUNEL-positive nuclei showed condensed chromatin and apoptotic bodies. Immunohistochemical studies of IEG expression performed at 3 h exhibited a marked induction of c-Fos, c-Jun, and Krox-24 protein in all sectors of the hippocampus, peaking in vulnerable CA1 pyramidal neurons and in dentate gyrus. In contrast, sham-operated animals (n=3) did not reveal neuronal degeneration or increased IEG expression in the hippocampus when compared with untreated control animals (n=3). In conclusion, we present a new model of global cerebral ischemia and reperfusion in mice with the use of complete cardiocirculatory arrest and subsequent CPR. Following 5 min of ischemia, a subset of CA1 pyramidal neurons was TUNEL-positive at 7 days. The expression of IEG was observed in all sectors of the hippocampus, including selectively vulnerable CA1 pyramidal neurons. This appears to be a good model which should be useful in evaluating the role of various genes in transgenic and knockout mice following global ischemia.     

Postischemic administration of idazoxan, an alpha-2 adrenergic receptor antagonist, decreases neuronal damage in the rat brain

The effect of an alpha-2 receptor antagonist, idazoxan, on ischemic neuronal damage in the hippocampus and neocortex was studied in rats following 10 min of forebrain ischemia. Idazoxan was given 0.1 mg/kg i.v. immediately after recirculation, followed by 48 h of continuous infusion at a rate of 10 micrograms/kg/min. A histopathological examination of the CA1 region of the dorsal hippocampus and neocortex from each hemisphere was made on paraffin-embedded sections following 7 days of survival. In ischemic animals receiving an infusion of saline, 71% of the neurons in the hippocampal CA1 region were degenerated. In contrast, in the idazoxan-treated animals only 31% of the neurons were irreversibly damaged (p less than 0.01). We conclude that postischemic administration of the alpha-2 antagonist idazoxan protects neurons against damage following cerebral ischemia. Rapid postischemic administration of alpha-2 adrenergic receptor antagonists could be an effective treatment after stroke and cardiac arrest.     

DNA fragmentation in the CA2 sector of gerbil hippocampus following transient forebrain ischemia

It has been reported that following transient forebrain ischemia in the gerbil, "delayed neuronal death" and "reactive change" occur in hippocampal CA1 and CA2 sectors, respectively. In the present study, using the gerbil transient forebrain ischemia model, we examined brain sections after various recirculation periods and demonstrated, employing the in situ nick-end labeling (TUNEL) method, a nuclear DNA fragmentation in the damaged CA2 neurons.     

Failure of preventive effects of 2-deoxy- -glucose on ischemia-induced gerbil hippocampal neuronal damage by induced hyperthermia

Post-ischemic administration of 2-deoxy- -glucose (2-DG), a glucose antimetabolite, markedly reduces the occurrence of ischemia-induced delayed neuronal death (DND) in the gerbil hippocampus. This means that the reduction of energy dependent metabolism after ischemia prevents ischemia-induced damages of hippocampal neurons. In the present study, we demonstrated hyperthermia during ischemia fails to preserve neurons in hippocampal CA1 of 2-DG treated gerbil following transient forebrain ischemia.