Neuroprotective effects of lamotrigine in global ischemia in gerbils. A histological, in vivo microdialysis and behavioral study

A sudden surge in the release of glutamate is currently believed to be an important initiating step in neuronal damage due to an ischemic insult. In this experiment, we tested the efficacy of neuroprotection with lamotrigine, a novel antiepileptic drug that blocks voltage gated sodium channels and inhibits the ischemia-induced release of glutamate in the gerbil forebrain model of cerebral ischemia. The medication was administered 30 min before and 30 min after the insult in two groups of animals. Histological assessment of neuronal damage was evaluated at 7 and 28 days after the ischemic insult. Animals evaluated at 28 days also underwent behavioral testing. Microdialysis was used in the same model to study the response of ischemia-induced glutamate in saline treated controls versus animals treated with lamotrigine 20 min before the insult. There was highly significant neuronal protection in animals who were treated with lamotrigine either before or after the insult. Protection was seen both at 7 and 28 days after the insult. Behavioral testing also showed significantly better recovery in both sets of animals in comparison to the saline-treated group. Microdialysis confirmed a significant attenuation of the ischemia-induced glutamate surge when compared to the saline-treated animals. Our morphological, behavioral and microdialysis experiments show that lamotrigine offers significant neuroprotection from the effects of transient forebrain ischemia in gerbils. Neuroprotection with post-ischemic therapy probably depends on preserving the capacity of the sodium/calcium exchanger to reduce intracellular calcium concentrations or persistent `toxicity' of glutamate in the reperfusion period on the already `primed' injured neurons. These concepts need further study.     

Neuroprotective effect of tiagabine in transient forebrain global ischemia: an in vivo microdialysis,behavioral, and histological study

The neuroprotective effect of tiagabine was investigated in global ischemia in gerbils. Two groups of the animals received 15 mg/kg of tiagabine 30 min before ischemia. In the first group, the temperature was controlled at 37 degrees C from time of injection to 1 h after ischemia. In the second group, the temperature was left uncontrolled to see the hypothermic effect of tiagabine. Microdialysis was performed in CA1 region of hippocampus in half of the animals in each group to assess the levels of glutamate and gamma-amino-butyric acid (GABA). Animal behavior was also tested in 28-day groups in a radial-arm maze. Histology was done 7 and 28 days after ischemia in CA1 region of hippocampus to assess early and delayed effect of drug. A significant suppression of glutamate was noted in both groups (P<0.01). Behavioral results showed that in the temperature-uncontrolled treatment group, animals significantly reduced their working memory errors as compared to the temperature-controlled treatment group. Histology revealed a significant neuroprotection (P<0.001) in the temperature-uncontrolled treatment group. In the temperature-controlled treatment group, however, neuroprotection was insignificant (P>0.05). A third group of animals received the same dose of tiagabine 3 h after ischemia. Temperature was not controlled in this group. The animals were sacrificed after 7 days so no behavior testing was carried out. Histology showed no neuroprotection in this group (P>0.05). These results show that tiagabine offers a significant neuroprotection in global ischemia in gerbils when given 30 min before ischemia but not when given 3 h after ischemia.     

Gamma-vinyl GABA prevents hippocampal and substantia nigra reticulata damage in repetitive transient forebrain ischemia

GABAergic inhibitory mechanisms may offer protection to neurons after global ischemia. We tested the effects of γ-vinyl GABA, a GABA-transaminase inhibitor, via continuous infusion in the third ventricle (Alza pumps) in a gerbil model of repetitive forebrain ischemia. We used two episodes of 3 min duration with a ’reperfusion’ interval of 1 h between the insults. Histological analysis was done with silver staining 5 days after the insult. Our results show that there is significant protection of the hippocampus CA1 region and substantia nigra reticulata in treated animals compared to controls. An increase in GABA levels, decrease in glutamate, or mild hypothermia, may be potential mechanisms for this protection. GABAergic agents may prove useful agents in repetitive ischemia.     

Postischemic inhibition of GABA reuptake by tiagabine slows neuronal death in the gerbil hippocampus

The neuroprotective effects of enhancing neuronal inhibition with a γ-aminobutyric acid (GABA) uptake inhibitor were studied in gerbil hippocampus following transient ischemia. We used in vivo microdialysis to determine a suitable dosing regimen for tiagabine (NNC 328) to elevate extracellular levels of GABA within the hippocampus. In anesthetized (normothermic) gerbils, tiagabine (45 mg/kg, i. p.) selectively elevated extracellular GABA levels 450% in area CA1 of the hippocampus. In gerbils subjected to cerebral ischemia via 5-min bilateral carotid occlusion, extracellular GABA levels increased 13-fold in area CA1, returning to baseline within 30–45 min. When tiagabine was injected 10 min following onset of reperfusion, GABA levels remained elevated (200–470%) for 90 min. In addition, tiagabine significantly reduced the ischemic-induced elevation of glutamate levels in area CA1 during the postischemic period when GABA levels were elevated. There was no effect of postischemic tiagabine on aspartate or six other amino acids. Using the same dosing regimen, we evaluated the degree of neuroprotection in the hippocampus of gerbils 4 and 21 days after ischemia. Tiagabine decreased body temperature a maximum of 2.7°C beginning 30 min into reperfusion and lasting 90 min. In untreated gerbils sacrificed 4 and 21 days after ischemia, there was severe necrosis (99%) of the pyramidal cell layer in area CA1. Whereas tiagabine significantly protected the CA1 pyramidal cell layer in ischemic gerbils at 4 days (overt necrosis confined to about 17% of area CA1), the protection diminished significantly 21 days postischemia. When normothermia was maintained both during and after ischemia in a separate group of tiagabine-treated animals, approximately 77% of the CA1 pyramidal cell layer was necrotic at 4 days. Based on these findings, we suggest that (1) tiagabine slows the development of hippocampal degeneration following ischemia, and (2) that mild, postischemic hypothermia is responsible, in large part, for the neuroprotective actions of this drug. We conclude that the histological outcome after administration of cerebral neuroprotectants should be assessed following long-term survival. © 1995 Wiley-Liss, Inc.     

GABA Agonist "Muscimol" Is Neuroprotective in Repetitive Transient Forebrain Ischemia in Gerbils

The damaging effects from transient forebrain ischemia may be a result of excessive excitability or loss of inhibitory influences. In the brain, GABA acts as the major inhibitory neurotransmitter and its loss may be an important factor leading to delayed neuronal damage in the substantia nigra reticulata (SNr). In this study, we looked at the protective effects of muscimol, a GABA A agonist in a gerbil model of repetitive forebrain ischemia. For cerebral ischemia, we used three episodes of 2 min with a reperfusion period of 1 h between the insults. Histological evaluations were done 7 days after the insult using silver degeneration staining. Muscimol was infused into the third ventricle continuously for 7 days beginning just prior to the insult. There were a total of 20 animals, 12 treated with muscimol and the other 8 serving as controls. At 7 days, there was significant protection in the cortex (P = 0.007), hippocampus [CA1 (P = 0.01), CA4 (P = 0.015)], substantia nigra reticulata (P = 0.007), striatum (P = 0.049), and thalamus (P = 0.012). All statistical comparisons were done using nonparametric tests (Mann-Whitney U test). Our study shows that potentiation of inhibitory mechanisms may be important mechanisms of neuronal protection from the effects of repetitive ischemia and the effects are not limited to the SNr. Further studies are needed to better understand their mechanism of action.     

Gerbil hippocampal extracellular glutamate and neuronal activity after transient ischemia

In order to elucidate the role of glutamate in the pathogenesis of delayed neuronal death, we analyzed changes in extracellular levels of glutamate induced by transient ischemia in the Mongolian gerbil hippocampus by a new brain microdialysis method combined with an enzymatic cycling technique. We also studied the effect of this change in glutamate on CA1 spontaneous neuronal discharges. The level of glutamate significantly increased during the 5 min of ischemia and during the first 5 min of recirculation. However, neuronal hyperactivity anticipated as a result of the increased extracellular glutamate was not observed. Spike discharges disappeared during and shortly after 5 min of ischemia; CA1 spontaneous spike discharges reappeared about 15 min after the recirculation. The frequency and amplitude of the discharges of CA1 neurons returned to normal by 30 min of the recirculation. However, the pattern of discharges was different from that recorded before the ischemia. CA1 neurons were found dead 4 days after the ischemia. Brief exposure to toxic concentrations of glutamate may cause the delayed neuronal death.     

Neuroprotective effects of ischemic preconditioning on hippocampal CA1 pyramidal neurons through maintaining calbindin D28k immunoreactivity following subsequent transient cerebral ischemia

Ischemic preconditioning elicited by a non-fatal brief occlusion of blood flow has been applied for an experimental therapeutic strategy against a subsequent fatal ischemic insult. In this study, we investi-gated the neuroprotective effects of ischemic preconditioning (2-minute transient cerebral ischemia) on calbindin D28k immunoreactivity in the gerbil hippocampal CA1 area following a subsequent fatal tran-sient ischemic insult (5-minute transient cerebral ischemia). A large number of pyramidal neurons in the hippocampal CA1 area died 4 days after 5-minute transient cerebral ischemia. Ischemic preconditioning reduced the death of pyramidal neurons in the hippocampal CA1 area. Calbindin D28k immunoreactivity was greatly attenuated at 2 days after 5-minute transient cerebral ischemia and it was hardly detected at 5 days post-ischemia. Ischemic preconditioning maintained calbindin D28k immunoreactivity after transient cerebral ischemia. These findings suggest that ischemic preconditioning can attenuate transient cerebral ischemia-caused damage to the pyramidal neurons in the hippocampal CA1 area through maintaining cal-bindin D28k immunoreactivity.     

Ischemic preconditioning: a long term survival study using behavioural and histological endpoints

In this study we sought to determine if ischemic preconditioning provided long term behavioral and histological protection. A second goal was to see if ischemic preconditioning conveys its protective effect on CA1 neurons by altering post-ischemic brain temperature. While preconditioning episodes of short duration ischemia (i.e. 1.5 min) provided significant histological protection of CA1 pyramidal cells against a subsequent severe ischemic insult (i.e. 5 min), this did not result in complete behavioural protection. Preconditioned ischemic animals initially displayed habituation deficits in an open field test that were comparable to untreated ischemic gerbils. A significant decline in CA1 preservation in preconditioned animals was observed when survival time was extended from 10 (81% protection) to 30 (53% protection) days. In addition, protection was not observed in the subiculum and CA2 sector of the hippocampus where consistent damage was observed in 21/22 gerbils. Ischemic preconditioning did not markedly affect post-ischemic brain temperature suggesting that the observed protection was not due to a reduction in temperature during or after the severe ischemic insult. The lack of functional protection within the first 10 days after ischemia, along with the decline of cellular preservation over time, suggests that this paradigm may not provide permanent protection.     

Different dynamic patterns of extracellular glutamate release in rat hippocampus after permanent or 30‐min transient cerebral ischemia and histological correlation

The extent and severity of neuronal damage is different in ischemia with reperfusion compared to ischemia and no reperfusion. To investigate the role of glutamate in cerebral ischemia–reperfusion injury, in vivo microdialysis was performed to examine the dynamic profile of glutamate in the hippocampus in a transient (30 min) or permanent middle cerebral artery occlusion (MCAo) in Wistar rats. The extracellular concentration of glutamate in the cornu ammonis (CA)1 sector of the ipsilateral hippocampus showed a significant but transient elevation of glutamate for both groups immediately following ischemic insult. The initial high peak in glutamate levels in the transient MCAo group was followed by two secondary elevations in glutamate at 50 min and 90 min after initialization of reperfusion. The histopathological outcome was also different in the two groups. The observation that glutamate releases occurred in the early reperfusion phase provided an evidence of additional excitotoxicity of glutamate and thereby a therapeutic base for extended use of glutamate antagonist in the ischemia–reperfusion injury.     

Protection against ischemic hippocampal CAI damage in the rat with a new non-NMDA antagonist, NBQX

Two glutamate antagonists were tested in a rat model of complete, transient cerebral ischemia. Six days after 10 min ischemia the mean loss of hippocampal CA1 pyramidal neurones was 73%. Administration of the AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) antagonist NBQX (2,3-dihydro-6-nitro-7-sulfamoyl-benzo(F)quinoxaline) reduced the pyramidal neurone loss to 1%, 11% and 15%, when given before, immediately after or 1 h after ischemia, respectively. MK-801 (dizocilpine), a competitive NMDA antagonist gave no protection in this model. We suggest that the AMPA receptor transduction mechanisms are sensitized by ischemia and that the postischemic blockade of the main glutamatergic input to the CA1 cells with NBQX impairs the deleterious effect of "normal" postischemic excitatory transmission.     

Altered expression of the glutamate transporter EAAC1 in neurons and immature oligodendrocytes after transient forebrain ischemia.

Glutamate uptake is reduced during ischemia because of perturbations of ionic gradients across neuronal and glial membranes. Using immunohistochemical and Western blot analyses, the authors examined the expression of the glutamate transporters EAAC1, GLAST, and GLT-1 in the rat hippocampus and cerebral cortex 8 hours and 1 to 28 days after transient forebrain ischemia. Densitometric analysis of immunoblots of CA1 homogenates showed a moderate increase in EAAC1 protein levels early after the insult. Consistently, it was observed that EAAC1 immunostaining in CA1 pyramidal neurons was more intense after 8 hours and 1 day of reperfusion and reduced at later postischemia stages. A similar transient increase of EAAC1 immunolabeling was detected in layer V pyramidal neurons of the cerebral cortex. In addition, the authors observed that EAAC1 also was located in oligodendroglial progenitor cells in subcortical white matter. The number of EAAC1-labeled cells in this region was increased after 3 and 28 days of reperfusion. Finally, changes in GLAST and GLT-1 expression were not observed in the CA1 region after ischemia using immunohistochemical study or immunoblotting. Enhanced expression of EAAC1 may be an adaptive response to increased levels of extracellular glutamate during ischemia.     

Antioxidant-like protein 1 is altered in non-pyramidal cells and expressed in astrocytes in the gerbil hippocampal CA1 region after transient forebrain ischemia

In the present study, we observed chronological changes of antioxidant-like protein 1 (AOP-1) in the gerbil hippocampal CA1 region after 5 min of transient forebrain ischemia using immunohistochemistry and western blot. AOP-1 was significantly altered in the CA1 region after transient ischemia. In the sham-operated group, AOP-1 immunoreactivity was detected in pyramidal and non-pyramidal cells of the CA1 region. At 30 min after ischemic insult, AOP-1 immunoreactivity and protein level was decreased in the CA1 region. At 12 h after ischemic insult, AOP-1 immunoreactivity and protein level was highest in this region. At this time, after ischemia, AOP-1 immunoreactivity in non-pyramidal cells was high compared to the sham-operated group. Based on double immunofluorescence study, AOP-1-immunoreactive neurons were identified as GABAergic, which were stained with GAD or parvalbumin. Thereafter, AOP-1 immunoreactivity and protein levels were decreased time-dependently. From 4 days after ischemic insult, AOP 1 immunoreactivity was generally expressed in astrocytes. Five days after ischemic insult, AOP-1 immunoreactivity and protein level was increased again to 1.4 folds compared to that of the sham-operated group. In brief, AOP-1 immunoreactivity was increased in GABAergic non-pyramidal cells in the hippocampal CA1 region at early time after ischemic insult and was expressed in astrocytes at late time after ischemia. This result suggests that AOP-1 may be important role in homeostasis of GABAergic neurons because these neurons are resistant to ischemic damage.     

Time course of changes in pyridoxal 5'-phosphate (vitamin B6 active form) and its neuroprotection in experimental ischemic damage

In the present study, we investigated ischemia-induced changes of pyridoxal 5'-phosphate synthesizing enzyme and degrading enzyme and neuroprotective effects and roles of pyridoxal 5'-phosphate against ischemic damage in the gerbil hippocampal CA1 region. Pyridoxal 5'-phosphate oxidase and pyridoxal phosphate phosphatase immunoreactivities were changed in neurons up to 2 days after ischemia, while 4 days after ischemia their immunoreactivities were expressed in astrocytes. Pyridoxal 5'-phosphate oxidase immunoreactivity and its protein level were highest 12 h after ischemia, while those in pyridoxal phosphate phosphatase were highest 2 days after ischemia. Total activities of these enzymes were changed after ischemia, but specific activities of the enzymes were not altered. Treatment with pyridoxal 5'-phosphate into brains (4 microg/5 microl, i.c.v.) at 30 min before transient ischemia protected about 80% of CA1 pyramidal cells 4 days after ischemia and induced elevation of glutamic acid decarboxylase 67 immunoreactivity in the CA1 region. However, pyridoxal 5'-phosphate treatment into ischemic brains decreased GABA transaminase immunoreactivity in the CA1 region after ischemia. These results indicate that pyridoxal 5'-phosphate may be associated with the inhibitory discharge of GABA in the hippocampal CA1 neurons, and the increased level of GABA may protect hippocampal CA1 pyramidal cells from ischemic damage.     

Chronological alterations of neurofilament 150 immunoreactivity in the gerbil hippocampus and dentate gyrus after transient forebrain ischemia

In this study, we observed the chronological alterations of neurofilament 150 (NF-150) immunoreactivity in the gerbil hippocampus and dentate gyrus after 5 min transient forebrain ischemia. NF-150 immunoreactivity in the sham-operated group was mainly detected in mossy fibers and in the hilar region of the dentate gyrus. NF-150 immunoreactivity and protein contents of NF-150 and RT 97 (polyphosphorylation epitopes of neurofilament) were significantly decreased at 15 min after ischemic insult. Between 30 min and 12 h after ischemic insult, NF-150 immunoreactivity and protein content were significantly increased as compared with the sham-operated group. Thereafter, NF-150 immunoreactivity and protein content started to decrease. At 12 h after ischemic insult, unlike dentate gyrus, NF-150 immunoreactivity increased in pyramidal cells of the CA1 region. Thereafter, NF-150 immunoreactivity in the CA1 region started to decrease, and 4 days after ischemic insult, NF-150 immunoreactivity nearly was similar to that of the sham-operated group. These biphasic patterns of NF-150 immunoreactivity in the hippocampus and dentate gyrus are reverse correlated with that of the intracellular calcium influx. For calcium detection in the CA1 region, we also conducted alizarin red staining. Alizarin red positive neurons were detected in some neurons at 15-30 min after ischemic insult. At 12 h after ischemia, alizarin red positive neurons were decreased. Thereafter, alizarin red positive neurons started to decrease, but alizarin positive neurons were significantly increased in dying neurons 4 days after ischemia. These results suggest that ischemia-related changes of NF-150 expression may be caused by the calcium following transient forebrain ischemia.     

Postischemic neuroprotection in the ischemia-tolerant state gerbil hippocampus is associated with increased ligand binding to inhibitory GABA<Subscript>A</Subscript> receptors

Excitotoxic activation of glutamate receptors is thought to play a key role in delayed neuronal death (DND) of highly vulnerable hippocampal CA1 neurons after transient global ischemia. DND can be prevented by a short sublethal preconditioning (PC) stimulus. Recently, we demonstrated that ischemic PC, but not a single period of 5-min ischemia elicits a transient up-regulation of hippocampal [(3)H]muscimol binding to GABA(A) receptors. This indicates that activation of the GABAergic system may participate in the acquisition of neuroprotection. The present study was designed to test whether postischemic modulation of receptor binding also occurs in the ischemia-tolerant state, i.e., after a PC stimulus of 2.5-min ischemia and a subsequent normally lethal period of 5-min ischemia 4 days apart. Using receptor autoradiography, [(3)H]AMPA and [(3)H]muscimol binding to excitatory AMPA and inhibitory GABA(A) receptors was analyzed in hippocampal subfields CA1, CA3 and dentate gyrus at recirculation intervals of 30 min, 8, 24, 48, 96 h and 3 weeks. Postischemic hippocampal ligand binding to AMPA receptors remained unchanged at any time point investigated, but [(3)H]muscimol binding to GABA(A) receptors in CA1 neurons rendered tolerant to ischemia was up-regulated between 30 min and 48 h of recirculation. Our data suggest that a relative shift between excitatory and inhibitory neurotransmission may promote postischemic survival of CA1 neurons.     

High frequency discharges of gerbil hippocampal CA1 neurons shortly after ischemia

It has been postulated that the central neurotoxicity of glutamate participates in the pathogenesis of the ischemia-induced neuronal death and the process of the neuronal death is initiated by overexcitation or depolarization of postsynaptic neurons induced by increased extracellular glutamate during ischemia. In the present study, in order to know whether ischemic neurons show the overexcitation, we studied changes of CA1 neuronal discharges in gerbil hippocampus induced by transient forebrain ischemia (1-5 min) using an extracellular unit recording technique. CA1 neurons showed the high frequency discharges shortly after ischemic insult of 90 sec, however, these discharges did not induce neuronal death. Delayed neuronal death in the CA1 sector was observed in animals with 5-min ischemia which did not induce high frequency discharges. Neuronal depolarization with no spike discharge may persist during and shortly after 5-min ischemia and initiate the delayed neuronal death.     

Induction of tolerance against traumatic brain injury by ischemic preconditioning.

We tested the hypothesis that a transient non-lethal ischemic insult lasting 2 min would protect against subsequent moderate traumatic brain injury. Sprague-Dawley rats were randomized into three experimental groups, including sham ischemia procedures and ischemic preconditioning (IPC) followed 48 h later by moderate traumatic brain injury (TBI) provoked by parasagittal fluid percussion injury (1.8-2.1 atm) and IPC followed by 48 h sham TBI. Seven days after the secondary insult, animals were perfusion-fixed for quantitative histopathological analysis. The CA3 necrotic cell count was decreased by 63% in TBI animals that had undergone IPC as compared to TBI animals that underwent sham IPC. TBI animals that had undergone IPC demonstrated significantly smaller contusion volumes than the TBI alone group (6.44 +/- 1.51 vs 1.37 +/- 0.63 mm3, mean +/- s.e.m.) These data indicate that IPC applied 2 days before moderate fluid percussion brain injury increases the brain resistance to traumatic brain damage.     

沙鼠脑缺血耐受的组织学变化及HSP在其中的作用

目的 :观察脑缺血耐受时的组织学变化及 HSP在其中的作用。方法 :通过 HE染色观察脑缺血耐受时的组织学变化 ,并通过免疫组化染色 ,了解 HSP70及 HSP2 7在其中的作用。结果 :一次性 5分钟缺血后 7天海马 CA1区神经元大多坏死 ,若在缺血前给予 2分钟的缺血预处理 ,该区神经元大多保留 ,表现出明显的保护作用。只给一次性 5分钟缺血 ,海马 CA1区神经元无 HSP70染色。若在缺血前给予预处理 ,海马 CA1区神经元可见明显 HSP70染色。而HSP2 7主要在胶质细胞表达 ,海马区的神经元未见其表达。结论 :缺血前给予预处理对以后的缺血有保护作用 ;在缺血耐受过程中 ,HSP70表达出一定的保护作用。     

Continuing postischemic neuronal death in CA1: influence of ischemia duration and cytoprotective doses of NBQX and SNX-111 in rats

BACKGROUND AND PURPOSE: Transient forebrain ischemia results in a 24- to 72-hour delayed loss of CA1 neurons. Previous work has not assessed whether insult durations can vary the degree and maturation rate of CA1 injury and whether there are different ultrastructural features of death after brief or severe ischemia. We also tested whether known cytoprotective drugs achieve permanent or transient neuroprotection. METHODS: In the first experiment, ischemia was induced for 5, 15, or 30 minutes with the use of the 4-vessel occlusion rat model with 1- to 28-day survival. Others subjected to 5 or 15 minutes of ischemia and allowed to survive for 14 or 7 days, respectively, were examined with electron microscopy. Finally, we determined whether NBQX (30 mg/kg x3 at 0 or 6 hours after ischemia), an AMPA antagonist, and SNX-111 (5 mg/kg at 6 hours after ischemia), an N-type Ca2+ channel antagonist, provided enduring CA1 protection against 10 minutes of ischemia. RESULTS: CA1 damage was not detected at 24 hours. Thirty minutes of ischemia produced 47% and 84% CA1 damage at 2 and 3 days, respectively. A 15-minute occlusion yielded 11%, 74%, and 86% loss at 2, 3, and 7 days, respectively. Five minutes of ischemia produced an even slower progression with 24%, 52%, and 59% loss at 3, 7, and 14 days, respectively. Ultrastructural examination after 5 and 15 minutes of ischemia revealed necrosis with no morphological evidence of apoptosis. Both NBQX (P<0.021) and SNX-111 (P<0.001) significantly reduced CA1 death at 7 days (/=80%) compared with saline treatment ( approximately 79%). CONCLUSIONS: Brief forebrain ischemia results in a slower progression of CA1 loss than more severe insults. Nonetheless, neuronal injury had necrotic, not apoptotic, morphology. NBQX and SNX-111 only postponed CA1 injury.     

Baclofen is neuroprotective and prevents loss of calcium/calmodulin-dependent protein kinase II immunoreactivity in the ischemic gerbil hippocampus

Excessive release of glutamate during transient cerebral ischemia initiates a cascade of events that leads to the delayed and selective death of neurons located in the hippocampus. Activity of calcium calmodulin kinase II (CaM kinase), a protein kinase critical to neuronal functioning, disappears following ischemia. The in vivo link between glutamate excitoxicity and alterations in CaM kinase activity has not been extensively studied. Baclofen, a selective gamma-aminobutyric acid (GABA)(B) receptor agonist, has been shown to inhibit glutamate release. The present study evaluated the neuroprotective efficacy of this compound and assessed early changes in hippocampal-dependent behaviors and CaM kinase immunoreactivity following transient cerebral ischemia. Baclofen (50 mg/kg) prevented both the loss of hippocampal CA1 pyramidal cells and the reduction in hippocampal CaM kinase immunoreactivity observed in control animals following ischemic insult. Cerebral ischemia produced a significant increase in working memory errors; however, baclofen failed to attenuate this memory deficit. Results confirm that baclofen is neuroprotective and support a link between glutamate excitotoxicity and reductions in CaM kinase immunoreactivity.