Gerbil Hippocampal Neurons Research Articles

The role of JNK in IP-induced tolerance against forebrain ischemia/reperfusion injury in gerbils

Kitagawa等[1]在沙土鼠脑缺血的实验研究中,首次观察到机体对短暂亚致死性缺血的适应性反应能增加神经元对致死性缺血的耐受性,由此提出了脑缺血预处理(ischemic preconditioning, IP)的概念.此后各国学者对IP的机制进行了广泛的研究,提出了许多假说.近年来,以受体激活为起点,以细胞内信号转导为主线,构成预处理保护机制研究的重点,其中丝裂原激活的蛋白激酶(mitogen activated protein kinase, MAPK)途径在IP中的作用引起了人们的关注。

Adeno-associated virus vector-mediated bcl-2 gene transfer into post-ischemic gerbil brain in vivo: prospects for gene therapy of ischemia-induced neuronal death

The proto-oncogene bcl-2 is known as an anti-apoptotic gene that confers the ability to block neuronal cell death after transient ischemia. In order to examine whether the bcl-2 gene can be used for protection of ischemic brain injury, we generated adeno-associated virus (AAV) vectors capable of expressing human bcl-2. Replication-defective AAV vectors were found effectively to transfer and express bcl-2 gene in the gerbil hippocampal neurons. Transduction with AAV bcl-2 5 days before forebrain ischemia prevented the DNA fragmentation in the CA1 neurons that is commonly associated with ischemia-induced cell death. Furthermore, the application of AAV bcl-2 as late as 1 h following an ischemic insult also prevented DNA fragmentation in CA1 neurons. These results suggest that the bcl-2 protein has neuroprotective functions that inhibit ischemic cell death and demonstrate the potential of AAV bcl-2 for use in post-ischemic gene therapy in the brain. Gene Therapy (2000) 7, 1244-1249.

5-( N-Ethyl- N-isopropyl)-amiloride, an Na +–H + exchange inhibitor, protects gerbil hippocampal neurons from ischemic injury

The effect of the selective Na +/H + antiporter inhibitor 5-( N-ethyl- N-isopropyl)-amiloride (EIPA) on cerebral ischemia/reperfusion injury was evaluated in the Mongolian gerbil. Ischemia was induced in unanaesthetized gerbils by a 5-min period of bilateral common carotid artery occlusion followed by reperfusion for 6 days. Two groups of gerbils were injected intraperitoneally with either dimethyl sulfoxide (DMSO; 10 μl) or EIPA (5 mg/kg in 10 μl DMSO) 30 min prior to ischemia. The increase in locomotor activity in the EIPA-treated group was significantly less than that of the control group at both 24 h and 6-day post-ischemia. The extent of CA1 pyramidal neuron loss was significantly reduced in the EIPA-treated group in comparison with that of DMSO treated controls. These results suggest that EIPA can protect cerebral neurons from ischemia/reperfusion injury and implicates acidosis and Na +/H + exchange as a causative factor in such injury.

Improvement of ischemic damage in gerbil hippocampal neurons by procaine

Acute cerebral ischemia induces membrane depolarization in the neuron, thereby incurring the simultaneous influx of various ions such as Na + and Ca 2+. Since procaine possesses the ability to inhibit the release of Ca 2+ from intracellular Ca 2+ stores to the cytosol as well as the ability to block Na + channels, the effects of procaine on ischemia were investigated in the present study in gerbils both in vivo and in vitro. The histologic outcome was evaluated 7 days after 3 min of transient forebrain ischemia by assessing delayed neuronal death in hippocampal CA1 pyramidal cells in animals administered procaine (0.2, 0.4, or 2 μmol) intracerebroventricularly 10 min before ischemia and in animals given saline. The changes in the direct-current potential shift in the hippocampal CA1 area were measured using an identical animal model. A hypoxia-induced intracellular Ca 2+ increase was evaluated by in vitro microfluorometry in gerbil hippocampal slices, and the effects of procaine (10, 50, and 100 μmol/l) on the Ca 2+ accumulation were examined. Additionally, the effect of procaine (100 μmol/l) in a Ca 2+-free condition was investigated. The histologic outcome was improved and the onset of the ischemia-induced membrane depolarization was prolonged by the preischemic administration of procaine. The increase in the intracellular concentration of Ca 2+ induced by the in vitro hypoxia was suppressed by the perfusion of procaine-containing mediums (50 and 100 μmol/l), regarding both the initiation and the extent of the increase. A hypoxia-induced intracellular Ca 2+ elevation in the Ca 2+-free condition was observed, and the perfusion with procaine (100 μmol/l) inhibited this elevation. Procaine helps protect neurons from ischemia by suppressing the direct-current potential shift and by inhibiting the release of Ca 2+ from the intracellular Ca 2+ stores, as well as by inhibiting the influx of Ca 2+ from the extracellular space.

Induction of cyclooxygenase-2 mRNA in gerbil hippocampal neurons after transient forebrain ischemia

We examined the effect of brain ischemia on neuronal expression of cyclooxygenase-2 gene in the hippocampus. Transient forebrain ischemia was produced by occluding bilateral carotid arteries for 5 min in Mongolian gerbil. Northern blotting and in situ hybridization demonstrated that expression of cyclooxygenase-2 mRNA was transiently induced in the hippocampal neurons. Although future studies will be needed to clarify if induced cyclooxygenase-2 following ischemia is involved in neuronal damage or neuronal protection, selective cyclooxygenase-2 inhibitors may be a new therapeutical approach for the treatment of stroke.

Induction of cyclooxygenase-2 mRNA in gerbil hippocampal neurons after transient forebrain ischemia

We examined the effect of brain ischemia on neuronal expression of cyclooxygenase-2 gene in the hippocampus. Transient forebrain ischemia was produced by occluding bilateral carotid arteries for 5 min in Mongolian gerbil. Northern blotting and in situ hybridization demonstrated that expression of cyclooxygenase-2 mRNA was transiently induced in the hippocampal neurons. Although future studies will be needed to clarify if induced cyclooxygenase-2 following ischemia is involved in neuronal damage or neuronal protection, selective cyclooxygenase-2 inhibitors may be a new therapeutical approach for the treatment of stroke.

Expressions 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 CA1 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/mm). NGF immunoreactivity was normally present in the sham-control hippocampal neurons. However, it decreased in hippocampal CA1 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 CA1 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 CA1 and CA3 neurons and from 3 hr in the dentate gyrus. At 7 days, p75 NGFR immunoreactivity was expressed greatly in the surviving CA1 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 CA1 neurons after transient forebrain ischemia suggests that NGF and p75 NGFR may be involved in the mechanism of delayed neuronal death.

Ischemic tolerance can be induced repeatedly in the gerbil hippocampal neurons

We investigated whether ischemic tolerance can be induced repeatedly in the gerbil hippocampal neurons. The gerbils were firstly treated with two episodes of 2-min forebrain ischemia 1 day apart, which procedure is known to induce ischemic tolerance. After 4 weeks of recirculation, the animals were subjected to a 2-min period of preconditioning ischemia again and then to a 3-min period of ischemia after 3 days. The hippocampal CA1 neurons were destroyed 7 days after 3-min ischemia without the second preconditioning but not in animals with the second preconditioning. Thus, ischemic tolerance can be induced repeatedly when the first ischemic tolerance has disappeared.

Effect of transient forebrain ischemia on superoxide dismutases in gerbil hippocampus

Substantial generation of oxygen-derived free radicals has been implicated in pathophysiology of ischemic brain damage. Immunoreactive mitochondrial manganese and cytosolic copper-zinc superoxide dismutases, initial and essential enzymes to scavenge superoxide radical anions, increased in the gerbil hippocampal neurons after transient forebrain ischemia. Neuronal cells responded to oxidative stress in ischemia and induced the protective mechanism to increase superoxide dismutases.

Induced resistance and susceptibility to cerebral ischemia in gerbil hippocampal neurons by prolonged but mild hypoperfusion

Brief periods of non-lethal cerebral ischemia can induce resistance against subsequent lethal ischemia. In this study, asymptomatic gerbils after unilateral carotid artery ligation were subjected to 5 min of forebrain ischemia. The prolonged but mild hypoperfusion, by carotid occlusion, induced susceptibility at 1 day and tolerance at 30 days to lethal ischemia in the hippocampal neurons. The neuroprotective effect correlated well with induction of heat shock protein 72 in the hippocampal neurons. These results suggested that neuronal cells possess a cellular response to sublethal hypoperfusion and can survive forthcoming ischemic stress.

Influence of oxidative stress on induced tolerance to ischemia in gerbil hippocampal neurons

We investigated whether reversible oxidative stress induced by the administration of the superoxide dismutase inhibitor, diethyldithiocarbamate, could induce tolerance to subsequent cerebral ischemia in gerbil hippocampal neurons. Mature male gerbils received intraperitoneal injections of diethyldithiocarbamate (1.0 g/kg), which led to reduced superoxide dismutase activity and increases in thiobarbituric acid-reactive substance in the brain. Cerebral ischemia was produced by occluding the bilateral common carotid arteries for 5 min, either 2 or 4 days after diethyldithiocarbamate injection. One week after ischemia, samples from each brain were stained with hematoxylin-eosin to evaluate ischemic neuronal damage in the hippocampal CA1 sector. Diethyldithiocarbamate treatment 4 days before ischemia had significant protective effects against cerebral ischemia, while diethyldithiocarbamate 2-day pretreatment and vehicle treatment failed to show neuroprotection. Biochemical examinations showed a clear induction of heat shock protein 72 and a significant increase in manganese-containing superoxide dismutase in the hippocampus in animals treated with diethyldithiocarbamate 4 days prior to ischemia. These results suggested that the oxidative stress caused by diethyldithiocarbamate could induce tolerance to ischemia in the gerbil brain, and that the increase in the biosynthesis of manganese-containing superoxide dismutase and heat shock protein 72 could provide a biochemical explanation of the tolerance induced under these conditions.

Induced Tolerance to Ischemia in Gerbil Hippocampal Neurons

Brief ischemia induced tolerance to subsequent ischemia in the hippocampal neurons. Male Mongolian gerbils were subjected to 2 min of ischemia in an awake condition. This ischemic insult only rarely produced neuronal damage in the gerbil brain. One day (n = 9), 2 days (n = 9), or 4 days (n = 10) following the first brief ischemia, the animals (double-ischemia group) were subjected to the second ischemia for 5 min. The single-ischemia group received a sham procedure instead of the first ischemia and was identically subjected to the second ischemia 1 day (n = 9), 2 days (n = 10), and 4 days (n = 13) following the sham procedure. One week following the second ischemia, all gerbils were perfusion fixed and the neuronal density in the hippocampal CA1 sector was measured. In double-ischemia groups, the neuronal density per 1-mm length of the pyramidal cell layer was 103.4 +/- 93.1 (SD) in the 1-day subgroup, 125.6 +/- 64.2 in the 2-day subgroup, and 176.2 +/- 93.7 in the 4-day subgroup, while the density in normal gerbils was 254.7 +/- 18.6. The average neuronal density in the single-ischemia group was much lower than that in the double-ischemia group (whole control group: 10.9 +/- 27.4). Immunostaining using monoclonal antibody raised against 70-kDa heat-shock protein revealed an increase in 70-kDa heat-shock protein in the CA1 area following 2 min of ischemia. Very brief ischemia induces heat-shock proteins and, presumably, thereby renders neurons more tolerant to subsequent metabolic stress.