Protective effect of vinpocetine against brain damage caused by ischemia

The effects of vinpocetine against hippocampal neuronal damage and on local cerebral blood flow (LCBF) were examined in a rat model of forebrain ischemia (10-min occlusion of the carotid arteries and hypotension). Histological evaluation of neuronal loss in the hippocampus was performed 7 days after ischemia. LCBF was measured before ischemia as well as after 2 min and 1 hr of recirculation. Vinpocetine (10 mg/kg) administered pre- or post-ischemically reduced the hippocampal neuronal necrosis, while pre-ischemic administration of 2 or 20 mg/kg vinpocetine was ineffective. Since vinpocetine increased the LCBF after 1 hr of recirculation, it cannot be excluded that blood flow improvements contribute to its neuroprotective activity. On the other hand, there is no clear evidence that an elevation of post-ischemic hypoperfusion could protect neurons against ischemic damage. It is, therefore, suggested that vinpocetine acts directly on brain cells.     

Effects of emopamil on postischemic blood flow and neuronal damage in rat brain

Summary The effects of the calcium entry blocker emopamil on physiological variables, local cerebral blood flow (LCBF) and on hippocampal cell damage were evaluated after 10 min of forebrain ischemia in the rat. LCBF was determined with the ¹⁴C-iodoantipyrine technique after 2, 10, and 60 min of postischemic recirculation. Histological evaluation was performed 7 days after ischemia in cortical and hippocampal tissue by determination of the percentage of necrotic neurons. Preischemic application of emopamil [4 mg/kg racemate or 2 mg/kg (S)-emopamil; i.v.] caused increases in LCBF in cortical areas but did not alter blood flow in the hippocampus at 2 min of recirculation. After 10 and 30 min of flow resumption no differences in LCBF between drug-treated and control animals were observed. In the histological series (S)-emopamil was applied at doses of 2, 4 or 6 mg/kg before the induction of ischemia. After 7 days of postischemic recovery, neuronal damage was significantly reduced by the calcium antagonist in hippocampal CA 1 sector at all doses tested, the most prominent effects being observed with the lowest dose. At this dose cell loss in the Ca3 sector was also reduced. In cortical tissue the number of necrotic cells remained unchanged by emopamil treatment. It is concluded that the calcium antagonist emopamil can reduce ischemia-induced neuronal cell damage. The compound improves circulation in cortical tissue only during early recovery but not at later phases of reflow, i.e. the period of delayed hypoperfusion. These increases in blood flow are not of crucial importance for ultimate neuronal death in this area. The ameliorative action of emopamil on the survival of hippocampal neurons is not associated with blood flow changes and therefore seems to reflect a direct effect on cerebral parenchyma. Send offprint requests to G. W. Bielenberg at the above address     

Alterations of interneurons of the gerbil hippocampus after transient cerebral ischemia: effect of pitavastatin.

We investigated the immunohistochemical alterations of parvalbumin (PV)-expressing interneurons in the hippocampus after transient cerebral ischemia in gerbils in comparison with neuronal nitric oxide synthase (nNOS)-expressing interneurons. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor pitavastatin against the damage of neurons and interneurons in the hippocampus after cerebral ischemia. Severe neuronal damage was observed in the hippocampal CA1 pyramidal neurons 5 and 14 days after ischemia. The PV immunoreactivity was unchanged up to 2 days after ischemia. At 5 and 14 days after ischemia, in contrast, a conspicuous reduction of PV immunoreactivity was observed in interneurons of the hippocampal CA1 sector. Furthermore, a significant decrease of PV immunoreactivity was found in interneurons of the hippocampal CA3 sector. No damage of nNOS-immunopositive interneurons was detected in the gerbil hippocampus up to 1 day after ischemia. Thereafter, a decrease of nNOS immunoreactive interneurons was found in the hippocampal CA1 sector up to 14 days after ischemia. Pitavastatin significantly prevented the neuronal cell loss in the hippocampal CA1 sector 5 days after ischemia. Our immunohistochemical study also showed that pitavastatin prevented significant decrease of PV- and nNOS-positive interneurons in the hippocampus after ischemia. Double-labeled immunostainings showed that PV immunoreactivity was not found in nNOS-immunopositive interneurons of the brain. The present study demonstrates that cerebral ischemia can cause a loss of both PV- and nNOS-immunoreactive interneurons in the hippocampal CA1 sector. Our findings also show that the damage to nNOS-immunopositive interneurons may precede the neuronal cell loss in the hippocampal CA1 sector after ischemia and nNOS-positive interneurons may play some role in the pathogenesis of cerebral ischemic diseases. Furthermore, our present study indicates that pitavastatin can prevent the damage of interneurons in the hippocampus after cerebral ischemia. Thus, our study provides valuable information for the pathogenesis after cerebral ischemia.     

Differentially altered cerebral metabolism in ischemic rats by alpha2-adrenoceptor blockade and its relation to improved limb-placing reactions.

The selective alpha2-adrenoreceptor antagonist, atipamezole, improves behavioural performance of rats subjected to focal cerebral ischemia. The aim of the present study was to investigate whether the facilitatory effect of atipamezole on behaviour is related to altered neuronal activity in specific brain areas. The right middle cerebral artery of rats was occluded for 120 min using the intraluminal filament method. Starting on day 2 after induction of ischemia, atipamezole (1mg/kg, s.c.) or 0.9% NaCl was administered to ischemic or sham-operated rats once a day 30 min before the limb-placing test. [14C]Deoxyglucose ([14C]DG) uptake was used to measure neuronal activity 30 min after atipamezole or 0.9% NaCl administration on day 6 after ischemia. Ischemia induced a significant decrease in [14C]DG uptake in several cortical areas ipsilateral and contralateral to the lesion, in the ipsilateral thalamus, and bilaterally in the cerebellum and spinal cord. Administration of atipamezole normalised [14C]DG uptake particularly in the cerebellum and spinal cord both in sham-operated and ischemic rats and to a lesser extent in the thalamus in sham-operated rats. The pattern of altered cerebral [14C]DG uptake following alpha2-adrenoceptor blockade suggests that plasticity in the cerebellum and spinal cord contributes to the improved performance of ischemic rats in tests assessing tactile/proprioceptive limb-placing reactions.     

Delta opioid peptide [D-Ala2, D-Leu5] enkephalin (DADLE) triggers postconditioning against transient forebrain ischemia

Preconditioning with selective delta opioid peptide [d-Ala2, d-Leu5] enkephalin (DADLE) provides ischemic tolerance following transient forebrain ischemia in rats. However, whether DADLE postconditioning retains its neuroprotective efficacy and the underlying molecular mechanism in ischemic brain is largely unknown. We investigated DADLE postconditioning protection of hippocampal CA1 neurons against transient forebrain ischemia. 6 days after being implanted with cannula at the right lateral ventricle, rats underwent 10 min of forebrain ischemia by four vessel occlusion. Hippocampal CA1 neuronal survival and degeneration were measured in the hippocampi of rats at 3 days after ischemia. The behavioral and cognitive improvements of DADLE treatment in rats were also evaluated on days 5-9 using open-field and Morris water maze tests. The results showed that DADLE at doses of 0.25 and 2.5 nmol, but not 25 nmol, could significantly protect CA1 neurons against ischemia/reperfusion injury. Co-administration with the delta-opioid receptor antagonist naltrindole or pretreatment with the Akt antagonist LY294002 completely abolished the DADLE postconditioning effect. Furthermore, DADLE postconditioning exhibited cognitive benefits in rats with transient forebrain ischemia. The study thus suggested a therapeutic opportunity of postconditioning neuroprotection by DADLE and also provided important information in understanding the mechanism of DADLE action in the ischemic brain.     

Local cerebral glucose utilization and local cerebral blood flow in conscious rats after administration of flunarizine

Summary The effects of the calcium entry blocker flunarizine on physiologic variables, local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) were investigated. LCBF and LCGU were determined in 37 anatomically discrete brain regions in lightly restrained, conscious rats, using the quantitative, autoradiographic ¹⁴C-iodoantipyrine and ¹⁴C-2-deoxyglucose techniques. While 5 mg/kg flunarizine given i. v. did not change any of the measured physiologic variables, flunarizine increased LCBF in nearly all gray matter structures compared with saline-treated controls. LCGU was not changed compared to controls. In control as well as in flunarizine-treated rats coupling between LCGU and LCBF was tight. The ratio of LCBF/LCGU was increased after treatment with flunarizine. The data suggest that under normal physiological conditions the calcium entry blocker flunarizine does not change neuronal activity, but exerts primarily a cerebral vasodilating action. Send offprint requests to T. Beck address see above     

Neuroprotective efficacy of nimesulide against hippocampal neuronal damage following transient forebrain ischemia

Cyclooxygenase-2 is involved in the inflammatory component of the ischemic cascade, playing an important role in the delayed progression of the brain damage. The present study evaluated the pharmacological effects of the selective cyclooxygenase-2 inhibitor nimesulide on delayed neuronal death of hippocampal CA1 neurons following transient global cerebral ischemia in gerbils. Administration of therapeutically relevant doses of nimesulide (3, 6 and 12 mg/kg; i.p.) 30 min before ischemia and at 6, 12, 24, 48 and 72 h after ischemia significantly (P<0.01) reduced hippocampal neuronal damage. Treatment with a single dose of nimesulide given 30 min before ischemia also resulted in a significant increase in the number of healthy neurons in the hippocampal CA1 sector 7 days after ischemia. Of interest is the finding that nimesulide rescued CA1 pyramidal neurons from ischemic death even when treatment was delayed until 24 h after ischemia (34+/-9% protection). Neuroprotective effect of nimesulide is still evident 30 days after the ischemic episode, providing the first experimental evidence that cyclooxygenase-2 inhibitors confer a long-lasting neuroprotection. Oral administration of nimesulide was also able to significantly reduce brain damage, suggesting that protective effects are independent of the route of administration. The present study confirms the ability of cyclooxygenase-2 inhibitors to reduce brain damage induced by cerebral ischemia and indicates that nimesulide can provide protection when administered for up to 24 h post-ischemia.     

Activated astrocytes, but not pyramidal cells, increase glucose utilization in rat hippocampal CA1 subfield after ischemia.

The local cerebral glucose utilization (CMRglc) in the damaged rat hippocampal CA1 subfield increases 7 days after 10 min of cerebral ischemia. We have used the N-methyl-D-aspartate antagonist (NMDA antagonist) ketamine in rats 7 days after sham operation or cerebral ischemia to determine whether the elevated postischemic CMRglc of the CA1 subfield is due to long-lasting hyperexcitation of surviving or injured neurons, or, alternatively, to the metabolism of other cell types. The autoradiographic data were interpreted with the aid of histochemical analysis of the postischemic hippocampal cell changes. Anesthetic doses of ketamine significantly reduced the CMRglc in the CA1 strata oriens, pyramidale and radiatum of sham-operated rats, while the postischemic increases in CMRglc in these hippocampal CA1 strata were not affected by ketamine. In addition, there were ketamine-induced increases in the CMRglc of the CA1 stratum lacunosum moleculare of both sham-operated and postischemic rats. The immunoreactivity of the microtubule-associated protein 2 (MAP2), a postsynaptic protein marker, was decreased markedly in the CA1 subfield in postischemic rats, while the presynaptic protein marker, synaptophysin, remained the same in sham-operated and postischemic rats. The glial fibrillary acidic protein (GFAP) immunoreactivity of astrocytes raised markedly in the ischemically damaged CA1 subfield. Although it could be demonstrated that presynaptic terminals remain intact in the postischemic damaged CA1 subfield, the lacking ketamine effect on CA1 pyramidal neurons indicated that the increase in CMRglc in this brain area is not due to postsynaptic neural hyperexcitation, but probably has to be attributed to astrocytes activated by neuronal damage.     

Effects of hepatocyte growth factor on phosphorylation of extracellular signal-regulated kinase and hippocampal cell death in rats with transient forebrain ischemia

Hepatocyte growth factor (HGF) has been implicated in protection against several types of cell injuries. We investigated the effects of human recombinant HGF (hrHGF) on the selective neuronal cell death in the hippocampal CA1 region after transient forebrain ischemia in rats and explored the nature of the intracellular signaling pathway for the protection against this neuronal injury. hrHGF was injected continuously into the hippocampal CA1 region directly using an osmotic pump from 10 min to 72 h after the start of reperfusion. The marked increase in the number of TUNEL-positive cells found in the CA1 region after ischemia was almost completely abolished by the hrHGF treatment. Akt phosphorylation as well as IkappaB phosphorylation, which has been implicated in events downstream of the Akt, was not affected by hrHGF treatment. Extracellular signal-regulated kinase (ERK) phosphorylation was decreased in the CA1 region with time after ischemia. hrHGF increased or recovered ERK phosphorylation without changing the total amount of ERK protein. Immunohistochemical analysis demonstrated that phosphorylated ERK was colocalized with a neuronal nucleus marker NeuN in the hippocampal CA1 region of ischemic rats with hrHGF treatment at the early period after reperfusion. These results suggest that the protective effects of hrHGF against neuronal death in the hippocampal CA1 after transient forebrain ischemia could be related to an ERK-dependent pathway.     

Effects of buflomedil on survival rate, local cerebral blood flow and glucose utilization after cerebral ischemia in spontaneously hypertensive rats

Cerebral protective effects of oral Buflomedil administration for 7 days were studied in spontaneously hypertensive rats (SHR). After permanent bilateral carotid artery occlusion (BCAO), the survival rates at 24 hr were 38% and 44% in groups treated with Buflomedil at the doses of 30 mg/kg (n = 16) and 90 mg/kg (n = 15), respectively, which were significantly higher than that in the control group (orally given saline for 7 days), 6%. In rats that survived and given Buflomedil, carbon filling of the brain after BCAO was extended to the territories of the internal carotid artery, while it was restricted to the brainstem and cerebellum in rats died within 3 hr and given either saline or Buflomedil. Local cerebral blood flow (LCBF), monitored by [14C]-Iodoantipyrine autoradiography, was determined at 3 hr after the start of BCAO or at 2 hr after reperfusion in rats orally given either saline or Buflomedil 30 mg/kg for 7 days. Local cerebral glucose utilization (LCGU), monitored by [14C]-Deoxyglucose autoradiography, was determined at 2 hr after reperfusion. At 3 hr after the start of BCAO, the LCBF in the Buflomedil group was higher by 71-128% in the cerebral cortex, 61-150% in the amygdala, caudate-putamen, nucleous accumbens and globus pallidus, and 82% in the internal capsule. At 2 hr after reperfusion, LCBF did not differ between groups, but LCGU in the Buflomedil group was significantly higher by 26-49% in the cerebral cortex, cochlear nuclei and vestibular nuclei than that in the control group. From these results, it is concluded that Buflomedil improved survival rate after permanent BCAO and have beneficial effect on local cerebral blood flow distribution after BCAO in SHR.     

A Phytochemically characterized extract of Cordyceps militaris and cordycepin protect hippocampal neurons from ischemic injury in gerbils

In the present study, we investigated effects of the dried, hot-water extract of Cordyceps militaris (CME) and its major metabolite (cordycepin) against ischemic damage. The repeated treatment with CME protected hippocampal CA1 pyramidal neurons from ischemic damage in gerbils. The treatment with CME or cordycepin in gerbils reduced 4-hydroxy-2-nonenal (a marker of lipid peroxidation) immunoreactivity and levels in the ischemic CA1 region. Glial fibrillary acidic protein immunoreactive astrocytes and ionized calcium-binding adapter molecule 1 immunoreactive microglia in the vehicle-treated ischemic group were activated in the CA1 region 4 days after ischemia/reperfusion, whereas in the CME- or cordycepin-treated ischemic group, their activation was significantly decreased. These results suggest that the repeated treatment with CME protects against neuronal damage from ischemia/reperfusion by reducing oxidative damage.     

Effects of the indirect dopaminomimetic diethylpemoline on local cerebral glucose utilization and local cerebral blood flow in the conscious rat

The changes in local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) following the systemic application of the indirect dopaminomimetic diethylpemoline (50 mg/kg i.v.) were measured in conscious rats using the autoradiographic [14C]2-deoxyglucose and the [14C] iodoantipyrine technique. Increased rates of glucose utilization were observed in the sensorimotor cortex, parafascicular nucleus, ventrolateral nucleus of the thalamus, substantia nigra, caudate nucleus, globus pallidus, red nucleus, subthalamic nucleus, cerebellar cortex and vermis. Cingulate cortex, anteromedial, anteroventral nucleus of the thalamus, habenula and nucleus accumbens showed a decreased LCGU. The determination of LCBF revealed a similar pattern of altered blood flow values. Statistical evaluation of the relationship between glucose utilization and blood flow by regression analysis did not reveal any distinguishable difference between diethylpemoline-treated rats and controls. The data suggest that it is mainly the altered neuronal activity and metabolic demand after dopaminergic stimulation that effect the changes in blood flow rather than a direct dopaminergic effect on brain vasculature.     

HA1077, a novel calcium antagonistic antivasospasm drug, increases both cerebral blood flow and glucose metabolism in conscious rats.

The effects of a novel calcium antagonistic antivasospasm drug, HA1077, on local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) were studied in 33 anatomically discrete regions of the brain in conscious rats, using the quantitative autoradiographic [14C]iodoantipyrine and [14C]2-deoxyglucose techniques. HA1077 was infused i.v. over a 30-min period (1 or 3 mg/kg). HA1077 significantly increased LCBF in 9 of 33 sites in rats given 1 mg/kg, and in 14 of 33 sites in rats given 3 mg/kg compared to the control group given vehicle. Significant increases in LCGU were also noted in 16 of 33 sites in rats given 3 mg/kg. HA1077 increased both cerebral blood flow and glucose metabolism in conscious rats.     

Neuroprotective effects of thymoquinone against transient forebrain ischemia in the rat hippocampus

Increasing evidence demonstrates that oxidative stress plays an important role in brain injury in experimental models of brain ischemia. Thymoquinone, the main constituents of the volatile oil from Negella sativa seeds, is reported to possess strong antioxidant properties. Hence, the present study was undertaken to evaluate the neuroprotective effect of thymoquinone against transient forebrain ischemia-induced neuronal damage in the rat hippocampus. Rats were divided randomly into five groups: control, sham, ischemia, thymoquinone and ischemia+thymoquinone. Transient forebrain ischemia was induced with bilateral occlusion of both common carotid arteries for 10 min followed by 7 days of reperfusion. Thymoquinone was administered (5 mg/kg/day p.o.) 5 days before ischemia and continued during the reperfusion time. Animals were sacrificed, and brain tissues were isolated for histopathological examination. Hippocampal tissues were also used for determination of malondialdehyde levels, an end product of lipid peroxidation; glutathione (GSH) levels, a key antioxidant and the activities of the antioxidant enzymes catalase and superoxide dismutase (SOD). Thymoquinone and its metabolite thymohydroquinone were tested as inhibitors of the in vitro non-enzymatic lipid peroxidation induced by iron-ascorbate in the hippocampal homogenate. Forebrain ischemia-reperfusion neural injury in rats was demonstrated by histopathological observation, which revealed significant neural cell death in the hippocampus CA1 area 7 days post-ischemia (77% cell loss). Additionally, forebrain ischemia-reperfusion oxidative injury in rats was demonstrated by a significant increase in malondialdehyde and a significant decrease in GSH contents, catalase and SOD activities in the hippocampal tissue compared to the control or sham-operated groups. Pretreatment of thymoquinone attenuated forebrain ischemia-induced neuronal damage manifested by significantly decreasing the number of dead hippocampal neuronal cells (24% in thymoquinone-treated versus 77% for ischemia, P<0.001), which confirm the protective role of thymoquinone in ischemia-reperfusion injury. Also, pretreatment of ischemic rats with thymoquinone decreased the elevated levels of malondialdehyde and increased GSH contents, catalase and SOD activities to normal levels. Thymoquinone and thymohydroquinone inhibited the in vitro non-enzymatic lipid peroxidation in hippocampal homogenate induced by iron-ascorbate. The IC50 for thymoquinone and thymohydroquinone were found to be 12 and 3 microM respectively. This suggests that the protection of thymoquinone and its metabolite involve increased resistance to oxidative stress. In conclusion, thymoquinone is effective in protecting rats against transient forebrain ischemia-induced damage in the rat hippocampus. This spectacular protection makes thymoquinone a promising agent in pathologies implicating neurodegenaration such as cerebral ischemia.     

Preischemic administration of flunarizine or phencyclidine reduces local cerebral glucose utilization in rat hippocampus seven days after ischemia

The purpose of the present study was to investigate the influence of ischemia on postischemic metabolic activity of the brain. Furthermore, the effect of preischemic application of neuroprotective agents such as flunarizine or phencyclidine on postischemic local cerebral glucose utilization (LCGU) was examined. Forebrain ischemia in the rat was performed for 10 min with bilateral carotid clamping, administration of trimethaphan and blood withdrawal to obtain a mean arterial blood pressure of 40 mm Hg. LCGU was determined 7 days after ischemia by injecting 14C-deoxy-D-glucose in saline solution. A significant increase in LCGU in the CA1 subfield of the hippocampus was found 7 days after ischemia, whereas preischemic administration of flunarizine or phencyclidine inhibited this increase. Alterations in LCGU of other brain regions were insignificant.     

Neuroprotective effect of memantine demonstrated in vivo and in vitro

The purpose of the present study was to test whether the anticonvulsant, memantine (1-amino-3,5-dimethyladamantane), can protect neurons against hypoxic or ischemic damage. To this end, we used a rat model of transient forebrain ischemia and cultured neurons from chick embryo cerebral hemispheres. Ischemia was induced for 10 min by clamping both carotid arteries and lowering the mean arterial blood pressure to 40 mm Hg; the rats were allowed to recover for 7 days. Cultured neurons were made hypoxic with 1 mmol/l NaCN added to the incubation medium for 30 min followed by a recovery period of 3 days. The possible effects of memantine were compared with those produced by a typical non-competitive NMDA antagonist, dizocilpine. Similar effects were obtained with both drugs. The drugs reduced the damage caused by transient ischemia to neurons of the hippocampal CA1 subfield. Memantine (10 and 20 mg/kg) had a dose-dependent effect when administered intraperitoneally to the rats 1 h before ischemia. Dizocilpine was active in this model at a dosage of 1 mg/kg. When administered after ischemia, 10 mg/kg memantine significantly protected CA1 neurons against ischemic damage. Furthermore, the drugs protected cultured neurons against hypoxic damage. The lowest effective concentration was 0.1 mumol/l for dizocilpine and 1 mumol/l for memantine. Thus, memantine possesses neuroprotective activity but is less potent than dizocilpine.     

Failure of basic fibroblast growth factor to prevent postischemic neuronal damage in the rat.

It has been reported that basic fibroblast growth factor (bFGF) can increase neuronal survival and neurite extension, and that it further antagonizes the excitotoxicity of glutamate in in vitro hippocampal neurons. We examined the effects of bFGF on neuronal damage after transient forebrain ischemia. Rats were subjected to 20 min of cerebral ischemia in a four vessel occlusion model. Thirty minutes before induction of ischemia, bFGF (0.3-300 nM) or bFGF (300 nM) with heparin was applied to the hippocampal CA1 subfield. Morphological changes in the CA1 subfield were evaluated 7 days after ischemia and compared with those in the vehicle-injected group. A single injection of bFGF did not prevent postischemic neuronal damage in the hippocampal CA1, but these results do not rule out an effect of bFGF on neuronal damage after ischemia.     

缺血预处理对全脑缺血大鼠脑组织超微结构及细胞凋亡的影响

目的：为探讨脑缺血预处理对全脑缺血大鼠脑组织超微结构及细胞凋亡的影响。方法：本文以Wistar大鼠为受试对象,筛选后144只大鼠随机分为正常对照组(24只)、假手术组(24只)、脑缺血预处理对照组(32只)、脑缺血组(32只),脑缺血预处理组(32只)5组和术后12、24、48、72h四个时间点。采用“4-动脉阻断”方法建立大鼠全脑缺血模型,脑缺血后大脑皮层、海马CA1区HE染色观察组织形态学变化、电镜观察组织超微结构,原位末端标记(TUNEL染色)法检测神经元凋亡。结果：正常组、假手术组、脑缺血预处理对照组大脑皮层、海马CA1区无形态学改变,未见有细胞凋亡。脑缺血组大脑皮层、海马CA1区神经元缺失明显,12h、24h、48h、72h神经元凋亡逐渐加重。与脑缺血组相比,脑缺血预处理组大脑皮层、海马CA1区神经元损伤小,水肿程度轻,神经元形态恢复快,凋亡细胞数目少。结论：脑缺血预处理对全脑缺血大鼠大脑皮层、海马CA1区神经元具有保护作用,可以抑制全脑缺血大鼠大脑皮层、海马CA1区神经元凋亡。     

Post-ischaemic Alteration of Excitatory Amino Acid Transport Sites in the Gerbil Hippocampus

Sodium-dependent [³H]d -aspartate binding as a marker of excitatory amino acid transport sites in the gerbil hippocampus was evaluated by quantitative receptor autoradiography 1 h to 7 days after transient cerebral ischaemia for 10 min. Sodium-dependent [³H]d -aspartate binding in the hippocampal CA1 and CA3 sectors significantly increased in the early post-ischaemic stage. After 7 days, a conspicuous elevation of sodium-dependent [³H]d -aspartate-binding was observed in the hippocampal CA1 sector and dentate gyrus. However, no significant change in the binding was found in the hippocampal CA3 sector. A histological study revealed that transient ischaemia caused severe neuronal damage in the hippocampal CA1 sector and mild damage in the hippocampal CA3 sector. However, no ischaemic neuronal damage was observed in the dentate gyrus. An immunohistochemical study also showed that numerous reactive astrocytes were evident in the hippocampus, particularly in the hippocampal CA1 sector, 7 days after ischaemia. These results demonstrate that transient cerebral ischaemia can cause marked elevation in excitatory amino-acid transport sites in the hippocampus. Furthermore, our results suggest that the post-ischaemic increase in excitatory amino acid transport sites might reflect expression of reactive astrocytes. These findings are of interest in relation to the mechanisms of ischaemic hippocampal damage.     

Pre-ischemic Treatment with Ampicillin Reduces Neuronal Damage in the Mouse Hippocampus and Neostriatum after Transient Forebrain Ischemia

Ampicillin, a β-lactam antibiotic, has been reported to induce astrocytic glutamate transporter-1 which plays a crucial role in protecting neurons against glutamate excitotoxicity. We investigated the effect of ampicillin on neuronal damage in the mouse hippocampus and neostriatum following transient global forebrain ischemia. Male C57BL/6 mice were anesthetized with halothane and subjected to bilateral occlusion of the common carotid artery for 40 min. Ampicillin was administered post-ischemically (for 3 days) and/or pre-ischemically (for 3~5 days until one day before the onset of ischemia). Pre- and post-ischemic treatment with ampicillin (50 mg/kg/day or 200 mg/kg/day) prevented ischemic neuronal death in the medial CA1 area of the hippocampus as well as the neostriatum in a dose-dependent manner. In addition, ischemic neuronal damage was reduced by pre-ischemic treatment with ampicillin (200 mg/kg/day). In summary, our results suggest that ampicillin plays a functional role as a chemical preconditioning agent that protects hippocampal neurons from ischemic insult.