Neuroprotective effects of MK-801 in different rat stroke models for permanent middle cerebral artery occlusion: adverse effects of hypothalamic damage and strategies for its avoidance

Neuroprotective effects of MK-801 against cerebral ischemia reperfusion

Introduction

& Objective: Cerebral ischemia/reperfusion (I/R) injury, the second cause of death globally, involves increased NMDA receptor activity leading to neuronal damage due to excessive sodium and calcium ion entry. Therefore, targeting NMDA receptor may potentially reduce cell death induced by brain injury. Our study aimed to investigate the role of NMDA receptors in hippocampal neuronal activity induced by I/R.

Methods

In this study, Wistar rats were divided into four groups: sham, I/R, I/R + MK801, and I/R + NMDA. Cerebral I/R injury was induced by temporarily occluding the common and vertebral carotid arteries, followed by reperfusion. MK801 or NMDA was administered to the rats after a specific reperfusion time. Neuronal density and cell morphology in the hippocampal CA1 region were assessed using Nissl and H&E staining. The expression of BDNF, p-CREB, and c-fos was evaluated through Western blot analysis. Additionally, neuronal activity in CA1 pyramidal neurons were examined using single unit recording technique.

Results

Our results showed that cerebral I/R injury caused significant damage to CA1 pyramidal neurons compared to the sham group. However, treatment with MK-801 improved hippocampal cell survival compared to the I/R group. Furthermore, MK-801 administration in I/R rats increased BDNF, c-fos, and p-CREB levels while decreasing cleaved caspase-3 activity compared to the I/R group. Additionally, electrophysiological data showed that MK-801 increased firing rates of CA1 pyramidal neurons during the reperfusion phase.

Conclusion

MK-801 shows promise as a therapeutic agent for cerebral I/R injury by enhancing cell survival, upregulating neuroplasticity factors, and increasing firing rates of CA1 pyramidal neurons. It exerts a specific protective effect against cerebral I/R injury.

Stroke and Translational Research - Review of Experimental Models with a Focus on Awake Ischaemic Induction and Anaesthesia

Animal models are an indispensable tool in the study of ischaemic stroke with hundreds of drugs emerging from the preclinical pipeline. However, all of these drugs have failed to translate into successful treatments in the clinic. This has brought into focus the need to enhance preclinical studies to improve translation. The confounding effects of anaesthesia on preclinical stroke modelling has been raised as an important consideration. Various volatile and injectable anaesthetics are used in preclinical models during stroke induction and for outcome measurements such as imaging or electrophysiology. However, anaesthetics modulate several pathways essential in the pathophysiology of stroke in a dose and drug dependent manner. Most notably, anaesthesia has significant modulatory effects on cerebral blood flow, metabolism, spreading depolarizations, and neurovascular coupling. To minimise anaesthetic complications and improve translational relevance, awake stroke induction has been attempted in limited models. This review outlines anaesthetic strategies employed in preclinical ischaemic rodent models and their reported cerebral effects. Stroke related complications are also addressed with a focus on infarct volume, neurological deficits, and thrombolysis efficacy. We also summarise routinely used focal ischaemic stroke rodent models and discuss the attempts to induce some of these models in awake rodents.

Prophylactic Zinc Administration Combined with Swimming Exercise Prevents Cognitive-Emotional Disturbances and Tissue Injury following a Transient Hypoxic-Ischemic Insult in the Rat

Exercise performance and zinc administration individually yield a protective effect on various neurodegenerative models, including ischemic brain injury. Therefore, this work was aimed at evaluating the combined effect of subacute prophylactic zinc administration and swimming exercise in a transient cerebral ischemia model. The prophylactic zinc administration (2.5 mg/kg of body weight) was provided every 24 h for four days before a 30 min common carotid artery occlusion (CCAO), and 24 h after reperfusion, the rats were subjected to swimming exercise in the Morris Water Maze (MWM). Learning was evaluated daily for five days, and memory on day 12 postreperfusion; anxiety or depression-like behavior was measured by the elevated plus maze and the motor activity by open-field test. Nitrites, lipid peroxidation, and the activity of superoxide dismutase (SOD) and catalase (CAT) were assessed in the temporoparietal cortex and hippocampus. The three nitric oxide (NO) synthase isoforms, chemokines, and their receptor levels were measured by ELISA. Nissl staining evaluated hippocampus cytoarchitecture and Iba-1 immunohistochemistry activated the microglia. Swimming exercise alone could not prevent ischemic damage but, combined with prophylactic zinc administration, reversed the cognitive deficit, decreased NOS and chemokine levels, prevented tissue damage, and increased Iba-1 (+) cell number. These results suggest that the subacute prophylactic zinc administration combined with swimming exercise, but not the individual treatment, prevents the ischemic damage on day 12 postreperfusion in the transient ischemia model.

Drug-Induced Hyperglycemia as a Potential Contributor to Translational Failure of Uncompetitive NMDA Receptor Antagonists

Hyperglycemia is a comorbidity in 60–80% of stroke patients; nevertheless, neuroprotective drugs like NMDA receptor (NMDAR) antagonists are typically assessed in normoglycemic animals at the preclinical stage before they are approved to enter clinical trials. Interestingly, as a possible explanation for the translational failure of NMDAR antagonists, it was recently reported that stroke occurring during nighttime causes smaller infarctions in rodents and therefore has a smaller window for neuroprotection. To investigate why stroke occurring during different circadian phases confers a difference in severity, we reanalyzed the published source data and found that some mice that were used in the daytime have higher blood glucose than mice that were used in the nighttime. We then repeated the experiments but found no difference in blood glucose concentration or infarct volume regardless of the circadian phase during which stroke occurs. On the other hand, induction of hyperglycemia by glucose injection reproducibly increased stroke severity. Moreover, although hyperglycemia increases infarction volume, which presumably would provide a larger window for neuroprotection, uncompetitive NMDAR antagonists were unexpectedly found to exacerbate stroke outcome by worsening hyperglycemia. Taken together, our new data and reanalysis of the published source data suggested that blood glucose during stroke, rather than the circadian phase during which stroke occurs, affects the size of the ischemic infarction; moreover, we have revealed drug-induced hyperglycemia as a potential reason for the translational failure of uncompetitive NMDAR antagonists. Future trials for this class of neuroprotective drugs should monitor patients’ blood glucose at enrollment and exclude hyperglycemic patients.

Stroke injury induced by distal middle cerebral artery occlusion is resistant to N-methyl-d-aspartate receptor antagonism in FVB/NJ mice

Although N-methyl-d-aspartate receptor (NMDAR) antagonism has been shown to have a neuroprotective effect in many preclinical stroke models, the efficacy of this antiexcitotoxicity strategy in clinical trials in stroke patients has been disappointing. Interestingly, it has been reported that NMDAR antagonism is not neuroprotective in C57BL/6 mice subjected to distal middle cerebral artery occlusion (dMCAO), supporting the notion that whether these treatments are neuroprotective depends on the type of cerebral ischemia. However, because C57BL/6 mice are inherently resistant to excitotoxicity, the reported lack of neuroprotection could also be explained by the difference in the mouse strain studied rather than the stroke model used. Here we examined the neuroprotective efficacy of NMDAR antagonism in FVB/NJ mice, an excitotoxicity-prone mouse strain, subjected to dMCAO. Although C57BL/6 mice are known to have an excitotoxicity-resistant genetic background and FVB/NJ mice are known to have an excitotoxicity-prone genetic background, the infarct volume and density of neurodegenerating neurons were similar in the two mouse strains following dMCAO. In addition, none of the antiexcitotoxicity agents studied, including the canonical NMDAR antagonist MK801 and the therapeutic peptides Tat-NR2B9c and L-JNKI-1, protected the FVB/NJ mouse brain against ischemic damage induced by dMCAO. In conclusion, our data demonstrated that FVB/NJ mice are no more susceptible to cerebral ischemia than C57BL/6 mice and that NMDAR antagonism is ineffective in mice, even in an excitotoxicity-prone strain, subjected to dMCAO.

The Function of the NMDA Receptor in Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is one of the main forms of neonatal brain injury which could lead to neonatal disability or even cause neonatal death. Therefore, HIE strongly affects the health of newborns and brings heavy burden to the family and society. It has been well studied that N-methyl-D-aspartate (NMDA) receptors are involved in the excitotoxicity induced by hypoxia ischemia in adult brain. Recently, it has been shown that the NMDA receptor also plays important roles in HIE. In the present review, we made a summary of the molecular mechanism of NMDA receptor in the pathological process of HIE, focusing on the distinct role of GluN2A- and GluN2B-containing NMDA receptor subtypes and aiming to provide some insights into the clinical treatment and drug development of HIE.

Non-invasive treatment with near-infrared light: A novel mechanisms-based strategy that evokes sustained reduction in brain injury after stroke

Ischemic stroke is a debilitating disease that causes significant brain injury. While restoration of blood flow is critical to salvage the ischemic brain, reperfusion can exacerbate damage by inducing generation of reactive oxygen species (ROS). Recent studies by our group found that non-invasive mitochondrial modulation with near-infrared (NIR) light limits ROS generation following global brain ischemia. NIR interacts with cytochrome c oxidase (COX) to transiently reduce COX activity, attenuate mitochondrial membrane potential hyperpolarization, and thus reduce ROS production. We evaluated a specific combination of COX-inhibitory NIR (750 nm and 950 nm) in a rat stroke model with longitudinal analysis of brain injury using magnetic resonance imaging. Treatment with NIR for 2 h resulted in a 21% reduction in brain injury at 24 h of reperfusion measured by diffusion-weighted imaging (DWI) and a 25% reduction in infarct volume measured by T2-weighted imaging (T2WI) at 7 and 14 days of reperfusion, respectively. Additionally, extended treatment reduced brain injury in the acute phase of brain injury, and 7 and 14 days of reperfusion, demonstrating a >50% reduction in infarction. Our data suggest that mitochondrial modulation with NIR attenuates ischemia-reperfusion injury and evokes a sustained reduction in infarct volume following ischemic stroke.

Hypothermia but not NMDA receptor antagonism protects against stroke induced by distal middle cerebral arterial occlusion in mice

Excitotoxicity mediated by the N-methyl-D-aspartate receptor (NMDAR) is believed to be a primary mechanism of neuronal injury following stroke. Thus, many drugs and therapeutic peptides were developed to inhibit either the NMDAR at the cell surface or its downstream intracellular death-signaling cascades. Nevertheless, the majority of focal ischemia studies concerning NMDAR antagonism were performed using the intraluminal suture-induced middle cerebral arterial occlusion (MCAO) model, which produces a large cortical and subcortical infarct leading to hypothalamic damage and fever in experimental animals. Here, we investigated whether NMDAR antagonism by drugs and therapeutic peptides was neuroprotective in a mouse model of distal MCAO (dMCAO), which produces a small cortical infarct sparing the hypothalamus and other subcortical structures. For establishment of this model, mice were subjected to dMCAO under normothermic conditions or body-temperature manipulations, and in the former case, their brains were collected at 3-72 h post-ischemia to follow the infarct development. These mice developed cortical infarction 6 h post-ischemia, which matured by 24-48 h post-ischemia. Consistent with the hypothesis that the delayed infarction in this model can be alleviated by neuroprotective interventions, hypothermia strongly protected the mouse brain against cerebral infarction in this model. To evaluate the therapeutic efficacy of NMDAR antagonism in this model, we treated the mice with MK801, Tat-NR2B9c, and L-JNKI-1 at doses that were neuroprotective in the MCAO model, and 30 min later, they were subjected to 120 min of dMCAO either in the awake state or under anesthesia with normothermic controls. Nevertheless, NMDAR antagonism, despite exerting pharmacological effects on mouse behavior, repeatedly failed to show neuroprotection against cerebral infarction in this model. The lack of efficacy of these treatments is reminiscent of the recurrent failure of NMDAR antagonism in clinical trials. While our data do not exclude the possibility that these treatments could be effective at a different dose or treatment regimen, they emphasize the need to test drug efficacy in different stroke models before optimal doses and treatment regimens can be selected for clinical trials.

The role of TRPM2 channels in neurons, glial cells and the blood-brain barrier in cerebral ischemia and hypoxia

Stroke is one of the major causes of mortality and morbidity worldwide, yet novel therapeutic treatments for this condition are lacking. This review focuses on the roles of the transient receptor potential melastatin 2 (TRPM2) ion channels in cellular damage following hypoxia-ischemia and their potential as a future therapeutic target for stroke. Here, we highlight the complex molecular signaling that takes place in neurons, glial cells and the blood-brain barrier following ischemic insult. We also describe the evidence of TRPM2 involvement in these processes, as shown from numerous in vitro and in vivo studies that utilize genetic and pharmacological approaches. This evidence implicates TRPM2 in a broad range of pathways that take place every stage of cerebral ischemic injury, thus making TRPM2 a promising target for drug development for stroke and other neurodegenerative conditions of the central nervous system.

Increased Susceptibility to Ischemic Brain Injury in Neuroplastin 65-Deficient Mice Likely via Glutamate Excitotoxicity

Cell adhesion molecules (CAMs) are involved in synaptic plasticity and neuronal survival in the adult brain. Neuroplastin 65 (Np65), one member of the immunoglobulin superfamily of CAMs, is brain-specific and highly expressed in rodent forebrain. The roles of Np65 in synaptic plasticity have been confirmed, however, whether Np65 affects neuronal survival remains unknown. To address this gap, we generated, to our knowledge, the first Np65 knockout (KO) mice. By occluding middle cerebral artery to perform ischemic stroke model, we showed that Np65 KO mice exhibited more severe neurological deficits and larger infarction volume measured by TTC staining and more apoptotic cells confirmed by TUNEL staining compared to wild type (WT) mice. Besides, western blot analysis showed that the vesicular glutamate transporter-1(VGluT1), and N-Methyl D-Aspartate receptors, including NR1, NR2A, and NR2B were significantly increased in Np65 KO mice compared with WT mice. In contrast, vesicular gamma amino butyric acid transporter (VGAT) levels were unchanged in two genotypes after stroke. Additionally, phosphorylated-extracellular signal-regulated kinase 1/2 levels were significantly increased in Np65 KO mice compared with WT mice after stroke. Together, these results suggest that Np65 KO mice may be more susceptible to ischemic events in the brain.

Cognitive Dysfunction After Cardiac Surgery: Revisiting Etiology

Cognitive dysfunction remains a frequent complication of cardiac surgery. Despite many years of research, few preventive strategies and no definitive therapeutic options exist for the management of this troublesome clinical problem. This shortcoming may be secondary to an incomplete understanding of the pathophysiology and etiology of cognitive loss after cardiac surgery; a better understanding of the etiology is essential to finding new therapies. The etiology of cognitive dysfunction after cardiac surgery is multifactorial and includes cerebral microembolization, global cerebral hypoperfusion, systemic and cerebral inflammation, cerebral temperature perturbations, cerebral edema, and possible blood-brain barrier dysfunction, all superimposed on genetic differences in patients that may make them more susceptible to injury or unable to repair from injury once it has occurred. This review expands on these potential etiologies in detailing the evidence for their existence.

The potential utility of some legal highs in CNS disorders

Over the last decade there has been an explosion of new drugs of abuse, so called legal highs or novel psychoactive substances (NPS). Many of these abused drugs have unknown pharmacology, but their biological effects can be anticipated from their molecular structure and possibly also from online user reports. When considered with the findings that some prescription medications are increasingly abused and that some abused drugs have been tested clinically one could argue that there has been a blurring of the line between drugs of abuse and clinically used drugs. In this review we examine these legal highs/NPS and consider whether, based on their known or predicted pharmacology, some might have the potential to be clinically useful in CNS disorders.

The macrosphere model-an embolic stroke model for studying the pathophysiology of focal cerebral ischemia in a translational approach

The main challenge of stroke research is to translate promising experimental findings from the bench to the bedside. Many suggestions have been made how to achieve this goal, identifying the need for appropriate experimental animal models as one key issue. We here discuss the macrosphere model of focal cerebral ischemia in the rat, which closely resembles the pathophysiology of human stroke both in its acute and chronic phase. Key pathophysiological processes such as brain edema, cortical spreading depolarizations (CSD), neuroinflammation, and stem cell-mediated regeneration are observed in this stroke model, following characteristic temporo-spatial patterns. Non-invasive in vivo imaging allows studying the macrosphere model from the very onset of ischemia up to late remodeling processes in an intraindividual and longitudinal fashion. Such a design of pre-clinical stroke studies provides the basis for a successful translation into the clinic.

L-NIO as a novel mechanism for inducing focal cerebral ischemia in the adult rat brain

BACKGROUND

Ischemic stroke is the most frequent cause of persistent neurological disability in Western societies. New treatment strategies are required and effective in vivo models are crucial to their development.

NEW METHOD

The current study establishes a novel in vivo rat model of focal striatal ischemia using the vasoconstrictive agent N5-(1-iminoethyl)-L-ornithine (L-NIO). Adult male Sprague Dawley rats received a unilateral intrastriatal infusion of L-NIO in combination with jugular vein occlusion.

RESULTS

L-NIO infusion was associated with zero mortality, low surgical complexity and a reproducible infarct, providing advantages over established models of focal ischemia. The mean infarct volume of 8.5±5.3% of the volume of the contralateral striatum resulted in blood-brain barrier dysfunction, neuronal hypoxia and ongoing neurodegeneration. Further characteristics of ischemic stroke were exhibited, including robust microglia/macrophage and astroglial responses lasting at least 35 days post-ischemia, in addition to chronic motor function impairment.

COMPARISON WITH EXISTING METHODS

When compared to other models such as the MCAo models, the consistency in regions affected, high success rate, zero mortality, reduced surgical complexity and minimal welfare requirements of the L-NIO model make it ideal for initial high-throughput investigations into preclinical efficacy and proof of principle studies of acute ischemic stroke interventions.

CONCLUSION

We propose that the L-NIO rat model of focal striatal ischemia does not replace the use of other ischemic stroke models. Rather it provides a new, complementary tool for initial preclinical investigations into the treatment of ischemic stroke.

Brain infection with Staphylococcus aureus leads to high extracellular levels of glutamate, aspartate, γ-aminobutyric acid, and zinc

Staphylococcal brain infections may cause mental deterioration and epileptic seizures, suggesting interference with normal neurotransmission in the brain. We injected Staphylococcus aureus into rat striatum and found an initial 76% reduction in the extracellular level of glutamate as detected by microdialysis at 2 hr after staphylococcal infection. At 8 hr after staphylococcal infection, however, the extracellular level of glutamate had increased 12-fold, and at 20 hr it had increased >30-fold. The extracellular level of aspartate and γ-aminobutyric acid (GABA) also increased greatly. Extracellular Zn(2+) , which was estimated at ∼2.6 µmol/liter in the control situation, was increased by 330% 1-2.5 hr after staphylococcal infection and by 100% at 8 and 20 hr. The increase in extracellular glutamate, aspartate, and GABA appeared to reflect the degree of tissue damage. The area of tissue damage greatly exceeded the area of staphylococcal infiltration, pointing to soluble factors being responsible for cell death. However, the N-methyl-D-aspartate receptor antagonist MK-801 ameliorated neither tissue damage nor the increase in extracellular neuroactive amino acids, suggesting the presence of neurotoxic factors other than glutamate and aspartate. In vitro staphylococci incubated with glutamine and glucose formed glutamate, so bacteria could be an additional source of infection-related glutamate. We conclude that the dramatic increase in the extracellular concentration of neuroactive amino acids and zinc could interfere with neurotransmission in the surrounding brain tissue, contributing to mental deterioration and a predisposition to epileptic seizures, which are often seen in brain abscess patients.

Evidence for the use of isoflurane as a replacement for chloral hydrate anesthesia in experimental stroke: an ethical issue

Since an ethical issue has been raised regarding the use of the well-known anesthetic agent chloral hydrate, owing to its mutagenic and carcinogenic effects in animals, attention of neuroscientists has turned to finding out an alternative agent able to meet not only potency, safety, and analgesic efficacy, but also reduced neuroprotective effect for stroke research. The aim of this study was to compare the potential of chloral hydrate and isoflurane for both modulating the action of the experimental neuroprotectant MK801 and exerting analgesia. After middle cerebral artery occlusion in rats, no difference was observed in 24 h survival rate, success of ischemia, or infarct volume reduction between both anesthetics. However, isoflurane exerted a more pronounced analgesic effect than chloral hydrate as evidenced by formalin test 3 hours after anesthesia onset, thus encouraging the use of isoflurane in experimental stroke models.

Small molecule inhibitors in the treatment of cerebral ischemia

INTRODUCTION

Stroke is the world's second leading cause of death. Although recombinant tissue plasminogen activator is an effective treatment for cerebral ischemia, its limitations and ischemic stroke's complex pathophysiology dictate an increased need for the development of new therapeutic interventions. Small molecule inhibitors (SMIs) have the potential to be used as novel therapeutic modalities for stroke, since many preclinical and clinical trials have established their neuroprotective capabilities.

AREAS COVERED

This paper provides a summary of the pathophysiology of stroke as well as clinical and preclinical evaluations of SMIs as therapeutic interventions for cerebral ischemia. Cerebral ischemia is broken down into four mechanisms in this article: thrombosis, ischemic insult, mitochondrial injury and immune response. Insight is provided into preclinical and current clinical assessments of SMIs targeting each mechanism as well as a summary of reported results.

EXPERT OPINION

Many studies demonstrated that pre- or post-treatment with certain SMIs significantly ameliorated adverse effects from stroke. Although some of these promising SMIs moved on to clinical trials, they generally failed, possibly due to the poor translation of preclinical to clinical experiments. Yet, there are many steps being taken to improve the quality of experimental research and translation to clinical trials.

GADD34 induces cell death through inactivation of Akt following traumatic brain injury

Neuronal cell death contributes significantly to the pathology of traumatic brain injury (TBI) irrespective of the mode or severity of the injury. Activation of a pro-survival protein, Akt, is known to be regulated by an E3 ligase TRAF6 through a process of ubiquitination-coupled phosphorylation at its T308 residue. Here we show that upregulation of a pro-apototic protein, GADD34, attenuates TRAF6-mediated Akt activation in a controlled cortical impact model of TBI in mice. TBI induces the expression of GADD34 by stimulating binding of a stress inducible transcription factor, ATF4, to the GADD34 promoter. GADD34 then binds with TRAF6 and prevents its interaction with Akt. This event leads to retention of Akt in the cytosol and prevents phosphorylation at the T308 position. Finally, in vivo depletion of GADD34 using a lentiviral knockdown approach leads to a rescue of Akt activation and markedly attenuates TBI-induced cell death.

Flat-panel volumetric computed tomography in cerebral perfusion: evaluation of three rat stroke models

Flat-panel volumetric computed tomography (fpVCT) is a non-invasive approach to three-dimensional small animal imaging. The capability of volumetric scanning and a high resolution in time and space enables whole organ perfusion studies. We aimed to assess feasibility and validity of fpVCT in cerebral perfusion measurement with impaired hemodynamics by evaluation of three well-established rat stroke models for temporary and permanent middle cerebral artery occlusion (MCAO). Male Wistar rats were randomly assigned to temporary (group I: suture model) and permanent (group II: suture model; III: macrosphere model) MCAO and to a control group. Perfusion scans with respect to cerebral blood flow (CBF) and volume (CBV) were performed 24h post intervention by fpVCT, using a Gantry rotation time of 1s and a total scanning time of 30s. Postmortem analysis included infarct-size calculation by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Infarct volumes did not differ significantly throughout intervention groups. After permanent MCAO, CBF significantly decreased in subcortical regions to 78.2% (group II, p=0.005) and 79.9% (group III, p=0.012) and in total hemisphere to 77.4% (group II, p=0.010) and 82.0% (group III, p=0.049). CBF was less impaired with temporary vessel occlusion. CBV measurement revealed no significant differences. Results demonstrate feasibility of cerebral perfusion quantification in rats with the fpVCT, which can be a useful tool for non-invasive dynamic imaging of cerebral perfusion in rodent stroke models. In addition to methodological advantages, CBF data confirm the macrosphere model as a useful alternative to the suture model for permanent experimental MCAO.

Ischemic stroke and neuroprotection

Stroke is a major cause of morbidity and mortality in both developed and developing countries of the world. Greater understanding of the pathophysiology of neuronal damage in ischemic stroke has generated interest in neuroprotection as a management strategy. This paper aims to review the current concept and place of neuroprotection in ischemic stroke. An extensive search of all materials related to the topic was made using library sources including Pubmed and Medline searches. Current research findings were also included. The findings are as presented. Neuroprotection is an increasingly recognized management strategy in ischemic stroke that promises to assist clinicians in reducing stroke mortality rates and improving the quality of life of survivors.

Characterization of the pattern of ischemic stroke induced by artificial particle embolization in the rat brain

Embolism is responsible for half of cerebral infarctions, yet few animal models were developed due to the unpredictability of the embolus-induced infarcts. We manufactured artificial embolic particles by blending chitin and poly(D,L-Lactide-co-glycolide) (chitin/PLGA) for their good biocompatibility and rapid hydration expansion property. We subdivided the chitin/PLGA microparticles into 10 size groups (from 38-45 μm to 255-350 μm) and injected them through the external carotid artery toward the bifurcation of the common carotid artery in the rat. Reduced blood flow of the ipsilateral hemisphere was evident immediately after the injection of particles. The spherical appearance of the particle was critical in occluding the cerebral vessels. Particle(212-250 μm) produced the greatest diffuse infarction in the ipsilateral hemisphere, including the cortex, hippocampus, basal ganglion, thalamus, midbrain and cerebellum. Particle(75-90 μm) induced single or sparse isolated infarcts mainly located in the subcortical region, resembling lacunar stroke observed in humans. Particle(38-45 μm) frequently crossed to the contralateral hemisphere and induced diffuse infarctions in both hemispheres. The cortex infarct volumes were positively correlated to neurologic score and seizure incidence. In conclusion, we have established embolic stroke animal models, including a novel model that mainly expresses lacunar infarction, by intravenous injection of chitin/PLGA microparticles.

Neuroprotective efficiency of NMDA receptor blockade in the striatum and CA3 hippocampus after various durations of cerebral ischemia in gerbils

The purpose of this study was to investigate neuroprotective efficiency of N-methyl D-aspartate (NMDA) receptor (NMDAR) blockade on the neuronal damage in the less studied and allegedly less affected CA3 hippocampus and striatum in the Mongolian gerbil model of global cerebral ischemia. The common carotid arteries of gerbils were occluded for 5, 10 or 15 minutes. Gerbils were given a low dose of non-competitive NMDA antagonist (MK-801, 3 mg/kg i.p.) or saline immediately after the occlusion in normothermic conditions. Neuronal damage was examined on 4th, 14th and 28th day after reperfusion. The effect of NMDAR blockade was followed in vivo by monitoring the neurological status of whole animals or at the cellular level by standard light- and confocal microscopy on brain slices. Increased duration of cerebral ischemia resulted in a progressive loss of striatal and CA3 hippocampal neurons. The most beneficial NMDAR blockade effect was observed when the neuronal damage was most severe - on the 28th day after 15-min ischemia. As judged by morphological and neurological data, the effect of ischemia is also apparent in the presumed less vulnerable regions (CA3 and striatum) which are functionally important in stroke plasticity. So, NMDAR blockade in normothermic conditions showed neuroprotective efficiency.

Dynamics of neuroinflammation in the macrosphere model of arterio-arterial embolic focal ischemia: an approximation to human stroke patterns

Background

Neuroinflammation evolves as a multi-facetted response to focal cerebral ischemia. It involves activation of resident glia cell populations, recruitment of blood-derived leucocytes as well as humoral responses. Among these processes, phagocyte accumulation has been suggested to be a surrogate marker of neuroinflammation. We previously assessed phagocyte accumulation in human stroke by MRI. We hypothesize that phagocyte accumulation in the macrosphere model may resemble the temporal and spatial patterns observed in human stroke.

Methods

In a rat model of permanent focal ischemia by embolisation of TiO₂-spheres we assessed key features of post-ischemic neuroinflammation by the means of histology, immunocytochemistry of glial activation and influx of hematogeneous cells, and quantitative PCR of TNF-α, IL-1, IL-18, and iNOS mRNA.

Results

In the boundary zone of the infarct, a transition of ramified microglia into ameboid phagocytic microglia was accompanied by an up-regulation of MHC class II on the cells after 3 days. By day 7, a hypercellular infiltrate consisting of activated microglia and phagocytic cells formed a thick rim around the ischemic infarct core. Interestingly, in the ischemic core microglia could only be observed at day 7. TNF-α was induced rapidly within hours, IL-1β and iNOS peaked within days, and IL-18 later at around 1 week after ischemia.

Conclusions

The macrosphere model closely resembles the characteristical dynamics of postischemic inflammation previously observed in human stroke. We therefore suggest that the macrosphere model is highly appropriate for studying the pathophysiology of stroke in a translational approach from rodent to human.

Why do we need multifunctional neuroprotective and neurorestorative drugs for Parkinson's and Alzheimer's disorders?

Parkinson's disease (PD) and Alzheimer's disease (AD) are severe neurodegenerative disorders, with no drugs that are currently approved to prevent the neuronal cell loss characteristic in brains of patients suffering from PD and AD, and all drug treatments are symptomatic and monomodal in their action. Due to the complex pathophysiology, including a cascade of neurotoxic molecular events that result in neuronal death and predisposition to depression and eventual dementia, and etiology of these disorders, an innovative approach towards neuroprotection or neurorestoration (neurorescue) is the development and use of multifunctional pharmaceuticals which can act at different brain regions and neurons. Such drugs target an array of pathological pathways, each of which is believed to contribute to the cascades that ultimately lead to neuronal cell death. In this short review, we discuss examples of novel multifunctional ligands that may have potential as neuroprotective-neurorestorative therapeutics in PD and AD, some of which are under development. The compounds discussed originate from synthetic chemistry as well as from natural sources.

Why do we need multifunctional neuroprotective and neurorestorative drugs for Parkinson's and Alzheimer's diseases as disease modifying agents

Parkinson's disease (PD) and Alzheimer's Disease (AD) are severe neurodegenerative disorders, with no drugs that are currently approved to prevent the neuronal cell loss characteristic in brains of patients suffering from PD and AD and all drug treatment are synptomactic. Due to the complex pathophysiology, including a cascade of neurotoxic molecular events that results in neuronal death and predisposition to depression and eventual dementia and etiology of these disorders, an innovative approach towards neuroprotection or neurorestoration (neurorescue) may be the development and use of multifunctional pharmaceuticals. Such drugs target an array of pathological pathways, each of which is believed to contribute to the cascades that ultimately lead to neuronal cell death. In this short review, we discuss examples of novel multifunctional ligands that may have potential as neuroprotective-neurorestorative therapeutics in PD and AD. The compounds discussed originate from synthetic chemistry as well as from natural sources.

Evaluation of the middle cerebral artery occlusion techniques in the rat by in-vitro 3-dimensional micro- and nano computed tomography

Background

Animal models of focal cerebral ischemia are widely used in stroke research. The purpose of our study was to evaluate and compare the cerebral macro- and microvascular architecture of rats in two different models of permanent middle cerebral artery occlusion using an innovative quantitative micro- and nano-CT imaging technique.

Methods

4h of middle cerebral artery occlusion was performed in rats using the macrosphere method or the suture technique. After contrast perfusion, brains were isolated and scanned en-bloc using micro-CT (8 μm)³ or nano-CT at 500 nm³ voxel size to generate 3D images of the cerebral vasculature. The arterial vascular volume fraction and gray scale attenuation was determined and the significance of differences in measurements was tested with analysis of variance [ANOVA].

Results

Micro-CT provided quantitative information on vascular morphology. Micro- and nano-CT proved to visualize and differentiate vascular occlusion territories performed in both models of cerebral ischemia. The suture technique leads to a remarkable decrease in the intravascular volume fraction of the middle cerebral artery perfusion territory. Blocking the medial cerebral artery with macrospheres, the vascular volume fraction of the involved hemisphere decreased significantly (p < 0.001), independently of the number of macrospheres, and was comparable to the suture method. We established gray scale measurements by which focal cerebral ischemia could be radiographically categorized (p < 0.001). Nano-CT imaging demonstrates collateral perfusion related to different occluded vessel territories after macrosphere perfusion.

Conclusion

Micro- and Nano-CT imaging is feasible for analysis and differentiation of different models of focal cerebral ischemia in rats.

MK-801 effect on regional cerebral oxidative stress rate induced by different duration of global ischemia in gerbils

We investigated MK-801 effect on ischemia-induced oxidative stress-the most important factor that exacerbates brain damage by reperfusion. The common carotid arteries of gerbils were occluded for 5, 10, or 15 min. Immediately after the occlusion, MK-801 (3 mg/kg i.p.) or saline were given in normothermic conditions. The MK-801 effects were followed in vivo by monitoring the neurological status of animals and at the intracellular level by standard biochemical assays. We investigated nitric oxide levels, superoxide production, superoxide dismutase activity, index of lipid peroxidation (ILP), and reduced glutathione content in hippocampus, striatum, forebrain cortex, and cerebellum. The measurements took place at different times (1, 2, 4, 7, 14, and 28 days) after reperfusion. Increased duration of cerebral ischemia resulted in a progressive induction of oxidative stress. Our results revealed pattern of dynamic changes in each oxidative stress parameter level which corresponded with ischemia duration in all tested brain structures. Most sensitive oxidative stress parameters were ILP and superoxide production. Our study confirmed spatial distribution of ischemia-induced oxidative stress. Tested brain structures showed different sensitivity to each oxidative stress parameter. As judged by biochemical and neurological data, applied MK-801 showed neuroprotective efficiency by reduction of ischemia-induced oxidative stress in brain.

Disruption of the axon initial segment cytoskeleton is a new mechanism for neuronal injury

Many factors contribute to nervous system dysfunction and failure to regenerate after injury or disease. Here, we describe a previously unrecognized mechanism for nervous system injury. We show that neuronal injury causes rapid, irreversible, and preferential proteolysis of the axon initial segment (AIS) cytoskeleton independently of cell death or axon degeneration, leading to loss of both ion channel clusters and neuronal polarity. Furthermore, we show this is caused by proteolysis of the AIS cytoskeletal proteins ankyrinG and betaIV spectrin by the calcium-dependent cysteine protease calpain. Importantly, calpain inhibition is sufficient to preserve the molecular organization of the AIS both in vitro and in vivo. We conclude that loss of AIS ion channel clusters and neuronal polarity are important contributors to neuronal dysfunction after injury, and that strategies to facilitate recovery must preserve or repair the AIS cytoskeleton.

Neither in vivo MRI nor behavioural assessment indicate therapeutic efficacy for a novel 5HT(1A) agonist in rat models of ischaemic stroke

Background

5HT_1A agonists have previously been shown to promote recovery in animal models of stroke using ex vivo outcome measures which have raised the hopes for a potential clinical implementation. The purpose of this study was to evaluate the potential neuroprotective properties of a novel 5HT_1A agonist DU123015 in 2 different models of transient focal ischaemic stroke of varying severities using both in vivo neuroimaging and behavioural techniques as primary outcome measures. For these studies, the NMDA receptor antagonist MK-801 was also utilized as a positive control to further assess the effectiveness of the stroke models and techniques used.

Results

In contrast to MK-801, no significant therapeutic effect of DU123015 on lesion volume in either the distal MCAo or intraluminal thread model of stroke was found. MK-801 significantly reduced lesion volume in both models; the mild distal MCAo condition (60 min ischaemia) and the intraluminal thread model, although it had no significant impact upon the lesion size in the severe distal MCAo condition (120 min ischaemia). These therapeutic effects on lesion size were mirrored on a behavioural test for sensory neglect and neurological deficit score in the intraluminal thread model.

Conclusion

This study highlights the need for a thorough experimental design to test novel neuroprotective compounds in experimental stroke investigations incorporating: a positive reference compound, different models of focal ischaemia, varying the duration of ischaemia, and objective in vivo assessments within a single study. This procedure will help us to minimise the translation of less efficacious compounds.

Why should we use multifunctional neuroprotective and neurorestorative drugs for Parkinson's disease?

Parkinson's disease (PD) is a severe neurodegenerative disorder, with no available drugs able to prevent the neuronal cell loss characteristic in brains of patients suffering from PD. Due to the complex cascade of molecular events involved in the etiology of PD, an innovative approach towards neuroprotection or neurorescue may entail the use of multifunctional pharmaceuticals that target an array of pathological pathways, each of which is believed to contribute to events that ultimately lead to neuronal cell death. Here we discuss examples of novel multifunctional ligands that may have potential as neuroprotective and neurorestorative therapeutics in PD. The compounds discussed originate from synthetic chemistry as well as from natural sources where various moieties, identified in research to possess neuroprotective and neurorestorative properties, have been introduced into the structures of several monomodal drugs, some of which are used in the clinic.

Aggravation of infarct formation by brain swelling in a large territorial stroke: a target for neuroprotection?

OBJECT

In territorial stroke vasogenic edema formation leads to elevated intracranial pressure (ICP) and can cause herniation and death. Brain swelling further impairs collateral blood flow to the ischemic penumbra and causes mechanical damage to adjacent brain structures. In the present study the authors sought to quantify the impact of this space-occupying effect on ischemic lesion formation.

METHODS

Wistar rats were assigned to undergo bilateral craniectomy or a sham operation and then were subjected to temporary middle cerebral artery occlusion (MCAO) for 90 minutes. A clinical evaluation and 7-T MR imaging studies were performed 5 and 24 hours after MCAO. The absolute brain water content was determined at 24 hours by using the wet/dry method.

RESULTS

Bilateral craniectomy before MCAO led to a drastic reduction in lesion volume at both imaging time points (p < 0.0001). Ischemic lesion volume was 2.7- and 2.3-fold larger in sham-operated animals after 5 and 24 hours, respectively. Clinical scores were likewise better in rats that had undergone craniectomy (p < 0.05). After 24 hours the midline shift differed significantly between the 2 groups (p < 0.001), but not after 5 hours. The relation between brain water content and ischemic lesion volume as well as the T2 relaxation time within the infarcted area was not different between the groups (p > 0.05).

CONCLUSIONS

The data indicated that collateral damage caused by the space-occupying effect of a large MCA territory stroke contributes seriously to ischemic lesion formation. The elimination of increased ICP thus must be regarded as a highly neuroprotective measure, rather than only a life-saving procedure to prevent cerebral herniation. Further clinical trials should reveal the neuroprotective potential of surgical and pharmacological ICP-lowering therapeutic approaches.

Use of an optimized transient occlusion of the middle cerebral artery protocol for the mouse stroke model

Intraluminal occlusion of the middle cerebral artery in rodents is widely used for investigating cerebral ischemia and reperfusion injury. Two types of filaments used for occlusion were tested in terms of surgical success, incidence of subarachnoid hemorrhage, and mortality: a standard 6-0 monofilament coated with methyl methacrylate glue (rigid probe) and an 8-0 monofilament coated with silicone (flexible probe). In 98 wild-type (WT) mice, the flexible probe produced significantly (P < .05) more successful strokes (73.5%) than the rigid probe (46.6%). The incidences of subarachnoid hemorrhage (3.7%) and mortality (5.6%) with the flexible probe were significantly lower than those with the rigid probe (26.6% and 11.1%, respectively). Rigid and flexible probes were also compared in heme oxygenase 1 knockout (n = 17) and WT littermates (n = 17), because knockout mice have been suggested to have more fragile blood vessels. All mice receiving the flexible probe had successful strokes, with no cases of subarachnoid hemorrhage or mortality; however, with the rigid probe, the success rate was only 80% in the WT mice and 60% in the knockout mice. The rates of subarachnoid hemorrhage and mortality were also significantly higher with the rigid probe in both genotypes, but the infarct volumes produced by each type of probe did not differ significantly between the 2 groups. We conclude that the flexible silicone-coated 8-0 probe is superior to the more rigid glue-coated probe, because it produces infarct volumes of equal size with a higher success rate and lower risk of subarachnoid hemorrhage and mortality.

Combination therapy of rosiglitazone, a peroxisome proliferator-activated receptor-gamma ligand, and NMDA receptor antagonist (MK-801) on experimental embolic stroke in rats

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists have been found to have potent anti-inflammatory actions and suggested as potential therapies for brain ischaemia. Glutamate is the most common excitatory neurotransmitter in the central nervous system and is released excessively during ischaemia. Stroke therapy will require combinations of drug classes, because no single drug class has yet been proven efficacious in human beings. The present study was conducted to assess whether N-methyl-d-aspartate (NMDA) receptor antagonist (MK-801) treatment can improve recovery from ischaemic brain injury and whether rosiglitazone, a PPAR-gamma ligand, can increase its neuroprotective effect in an embolic model of stroke. Stroke was induced in rats by embolizing a preformed clot into the middle cerebral artery. Rosiglitazone (0.1 mg/kg, intraperitoneally) and MK-801 (0.1 mg/kg, intravenously) were injected immediately after embolization. Forty-eight hours later, the brains were removed, sectioned and stained with triphenyltetrazolum chloride and analysed by a commercial image processing software programme. Rosiglitazone and MK-801 alone or in combination decreased infarct volume by 49.16%, 50.26% and 81.32%, respectively (P < 0.001). Moreover, the combination therapy significantly decreased the infarct volume when compared to any drug used alone (P < 0.05). MK-801 reduced the brain oedema by 68% compared to the control group (P < 0.05), but rosiglitazone or combination did not show any significant effect. The drugs alone or in combination also demonstrated improved neurological function, but combination therapy was more effective on neurological deficits improving. Our data show that the combination of MK-801 and rosiglitazone is more neuroprotective in thromboembolic stroke than given alone; this effect perhaps represents a possible additive effect in the brain infarction.

An improved automated method to quantitate infarct volume in triphenyltetrazolium stained rat brain sections

INTRODUCTION

The identification of acute neuroprotectants relies heavily on rodent stroke models. It is well know that some of the more common models used can exhibit a relatively high degree of inter animal variability. This necessitates the need to increase the sample size per group and to run concomitant positive and negative control groups with each study in order to increase the consistency and reproducibility of the model. As such, one aspect of these studies that has become more labor intensive is the measurement of infarct volume post study.

METHODS

Herein, we describe a simple method to determine stroke infarct volume in triphenyltetrazolium (TTC) stained brain sections utilizing an automated set of routines using standard software. The method was first validated by determining the correlation of infarct volumes derived from the manual measurements vs the automated method for the same samples across a wide range of infarcts.

RESULTS

This comparison resulted in a significant correlation (r=0.99) indicating that the automated method was a valid method to assess infarct volume across a wide range in lesion volumes. Next, the automated infarct analysis tool was used to determine the effect of (+)-MK801, a well known neuroprotectant, on infarct volume after cerebral ischemia. This study demonstrated a significant reduction in infarct volume in (+)-MK801 treated rats.

DISCUSSION

These data demonstrate a simple, accurate automated routine to measure lesion volume in TTC stained sections.

Multifunctional neuroprotective drugs targeting monoamine oxidase inhibition, iron chelation, adenosine receptors, and cholinergic and glutamatergic action for neurodegenerative diseases

A new paradigm is emerging in the targeting of multiple disease aetiologies that collectively lead to neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease, post-stroke neurodegeneration and others. This paradigm challenges the widely held assumption that 'silver bullet' agents are superior to 'dirty drugs' when it comes to drug therapy. Accumulating evidence in the literature suggests that many neurodegenerative diseases have multiple mechanisms in their aetiologies, thus suggesting that a drug with at least two mechanisms of action targeted at multiple aetiologies of the same disease may offer more therapeutic benefit in certain disorders compared with a drug that only targets one disease aetiology. This review offers a synopsis of therapeutic strategies and novel investigative drugs developed in the authors' own and other laboratories that modulate multiple disease targets associated with neurodegenerative diseases.

Serum S100B is a useful surrogate marker for long-term outcomes in photochemically-induced thrombotic stroke rat models

In recent years, serum S100B has been used as a secondary endpoint in some clinical trials, in which serum S100B has successfully indicated the benefits or harm done by the tested agents. Compared to clinical stroke studies, few experimental stroke studies report using serum S100B as a surrogate marker for estimating the long-term effects of neuroprotectants. This study sought to observe serum S100B kinetics in PIT stroke models and to clarify the association between serum S100B and both final infarct volumes and long-term neurological outcomes. Furthermore, to demonstrate that early elevations in serum S100B reflect successful neuroprotective treatment, a pharmacological study was performed with a non-competitive NMDA glutamate receptor antagonist, MK-801. Serum S100B levels were significantly elevated after PIT stroke, reaching peak values 48 h after the onset and declining thereafter. Single measurements of serum S100B as early as 48 h after PIT stroke correlated significantly with final infarct volumes and long-term neurological outcomes. Elevated serum S100B was significantly attenuated by MK-801, correlating significantly with long-term beneficial effects of MK-801 on infarct volumes and neurological outcomes. Our results showed that single measurements of serum S100B 48 h after PIT stroke would serve as an early and simple surrogate marker for long-term evaluation of histological and neurological outcomes in PIT stroke rat models.

Multifunctional neuroprotective–neurorescue drugs for Parkinson’s disease

Parkinson’s disease (PD) is a severe neurodegenerative disorder, with no drugs currently approved to prevent the neuronal cell loss characteristic of brains of patients suffering from PD. Owing to the complex etiology of PD, an innovative approach towards neuroprotection or neurorescue may be the use of multifunctional pharmaceuticals that target an array of pathological pathways, each of which is believed to contribute to the cascade that ultimately leads to neuronal cell death. In this review, we discuss examples of novel multifunctional ligands that may have potential as neuroprotective–neurorescue therapeutics in PD. The compounds discussed originate from synthetic chemistry as well as from natural sources.

A new method for superselective middle cerebral artery infusion in the rat

OBJECT

Selective intraarterial drug delivery is used to achieve enhanced local uptake with reduced systemic side effects. In the present paper the authors describe and characterize a new microcatheter-based model of superselective perfusion of the middle cerebral artery (MCA) in rats combined with blockade of blood flow through the MCA.

METHODS

Selectivity of administration was shown by infusion of Evans blue which diffusely stained the MCA territory, indicating an increased permeability of the blood-brain barrier during the blockade of blood flow to the MCA. Perfusion of autologous blood through the microcatheter resulted in a flow rate-related increase in the cerebral blood flow measured by laser Doppler flowmetry. Similarly, infusion of an artificial O2 carrier, Oxycyte, was accompanied by an increase in tissue oxygenation as measured using a Licox sensor. Blockade of blood flow to the MCA with the new microcatheter for an extended period of time resulted in the development of ischemia, which was comparable to that induced by intravascular occlusion using a silicone-coated thread. In a 24-hour MCA occlusion model, selective administration of a low dose of MK-801 (0.3 mg/kg body weight) resulted in a significantly smaller infarct volume than systemic application (339 +/- 53 mm(3) compared with 508 +/- 26 mm(3), p < 0.001).

CONCLUSIONS

This new model of superselective MCA infusion is a valuable tool for investigating the effect of selective delivery and enhanced drug uptake into cerebral ischemic tissue. Without constant blockade of blood flow through the MCA it may also be useful for enhanced drug uptake, gene transfer, or application of stem cells in other neuropathological conditions.

Cytokine secretion after cardiac surgery and its relationship to postoperative fever

A relationship between the inflammatory response to cardiopulmonary bypass (CPB) and fever after coronary artery bypass graft surgery (CABG) is assumed, but has not been studied. Therefore, we sought to assess the temporal pattern of cytokines' elevation and its association with post-CABG fever. In 355 primary elective CABG patients, serum cytokines (TNF-alpha, IL-1ra, IL-1beta, IL-6, and IL-8) were measured before surgery, at cessation of CPB and 2.5, 4.5, 24, and 48 h post-CPB. Fever was defined as a temperature >38 degrees C. TNF-alpha, IL-1beta and IL-8 peaked within the first 2.5 h after bypass, returning to near normal levels by 24h and increasing again by 48 h. IL-6 peaked early after bypass and remained elevated at 48 h. IL-1ra was elevated early, before returning to baseline by 24 h. Postoperative fever developed in 27% of patients. Increased IL-6 levels and male gender were significant predictors of fever (C-index=0.68; p=0.0003). No other cytokine showed a significant association with fever development. Of note is the previously undescribed bimodal pattern of cytokines' secretion after CABG. The association of fever with IL-6 levels suggests inflammatory mediation.

Serum S100B indicates successful combination treatment with recombinant tissue plasminogen activator and MK-801 in a rat model of embolic stroke

In recent years, serum S100B has been used as a secondary endpoint in some clinical trials in which serum S100B has successfully indicated the benefits or harm done by tested agents. However, few reports describe serum S100B as an indicator of the efficiency of neuroprotective treatment in experimental stroke models, although serum S100B may be as useful for histological and functional evaluations of neuroprotective treatments as in clinical trials. The present study seeks to investigate the possibility that serum S100B reflects successful combined treatment with rt-PA and MK-801 in an embolic stroke rat model. An embolic stroke model of rats was produced via intra-arterial autologous clot injection, after which serum S100B levels were measured 24 h after embolism and the association of serum S100B levels with brain edema volume and infarct volume investigated. Combination treatment with rt-PA and MK-801 significantly attenuated the elevation of serum S100B, which correlated significantly with reductions in brain edema resulting from combination treatment. These findings suggest that serum S100B is a simple and objective indicator for successful neuroprotective therapy and would help seeking partners for combination treatments with rt-PA in an embolic stroke rat model. Assessments of the efficacy of combination treatments with rt-PA and neuroprotectants using serum S100B would facilitate translational research bridging laboratory and bedsides because serum S100B functions as a common marker in both rats and human patients suffering from ischemic stroke.

Acute ischemic stroke: overview of major experimental rodent models, pathophysiology, and therapy of focal cerebral ischemia

Ischemic stroke is a devastating disease with a complex pathophysiology. Animal modeling of ischemic stroke serves as an indispensable tool first to investigate mechanisms of ischemic cerebral injury, secondly to develop novel antiischemic regimens. Most of the stroke models are carried on rodents. Each model has its particular strengths and weaknesses. Mimicking all aspects of human stroke in one animal model is not possible since ischemic stroke is itself a very heterogeneous disorder. Experimental ischemic stroke models contribute to our understanding of the events occurring in ischemic and reperfused brain. Major approaches developed to treat acute ischemic stroke fall into two categories, thrombolysis and neuroprotection. Trials aimed to evaluate effectiveness of recombinant tissue-type plasminogen activator in longer time windows with finer selection of patients based on magnetic resonance imaging tools and trials of novel recanalization methods are ongoing. Despite the failure of most neuroprotective drugs during the last two decades, there are good chances to soon have effective neuroprotectives with the help of improved preclinical testing and clinical trial design. In this article, we focus on various rodent animal models, pathogenic mechanisms, and promising therapeutic approaches of ischemic stroke.

Delta9-tetrahydrocannabinol (Delta9-THC) prevents cerebral infarction via hypothalamic-independent hypothermia

Delta(9)-tetrahydrocannabinol (Delta(9)-THC), a primary psychoactive constituent of cannabis, has been reported to act as a neuroprotectant via the cannabinoid CB(1) receptor. In this study, Delta(9)-THC significantly decreased the infarct volume in a 4 h mouse middle cerebral artery occlusion mouse model. The neuroprotective effect of Delta(9)-THC was completely abolished by SR141716, cannabinoid CB(1) receptor antagonist, and by warming the animals to 31 degrees C. Delta(9)-THC significantly decreased the rectal temperature, and the hypothermic effect was also inhibited by SR141716 and by warming to 31 degrees C. At 24 h after cerebral ischemia, Delta(9)-THC significantly increased the expression level of CB(1) receptor in both the striatum and cortex, but not in the hypothalamus. Warming to 31 degrees C during 4 h cerebral ischemia did not increase the expression of CB(1) receptor at the striatum and cortex in MCA-occluded mice. These results show that the neuroprotective effect of Delta(9)-THC is mediated by a temperature-dependent mechanism via the CB(1) receptor. In addition, warming to 31 degrees C might attenuate both the neuroprotective and hypothermic effects of Delta(9)-THC through inhibiting the increase in CB(1) receptor in both the striatum and cortex but not in the hypothalamus, which may suggest a new thermoregulation mechanism of Delta(9)-THC.

Multifunctional drugs with different CNS targets for neuropsychiatric disorders

The multiple disease etiologies that lead to neuropsychiatric disorders, such as Parkinson's and Alzheimer's disease, amyotrophic lateral sclerosis, Huntington disease, schizophrenia, depressive illness and stroke, offer significant challenges to drug discovery efforts aimed at preventing or even reversing the progression of these disorders. Transcriptomic tools and proteomic profiling have clearly indicated that such diseases are multifactorial in origin. Further, they are thought to be initiated by a cascade of molecular events that involve several neurotransmitter systems. In response to this complexity, a new paradigm has recently emerged that challenges the widely held assumption that 'silver bullet' agents are superior to 'dirty drugs' in therapeutic approaches aimed at the prevention or treatment of neuropsychiatric diseases. A similar pattern of drug development has occurred in strategies for the treatment of cancer, AIDS and cardiovascular diseases. In this review, we offer an overview of therapeutic strategies and novel investigative drugs discovered or developed in our own and other laboratories, that address multiple CNS etiological targets associated with an array of neuropsychiatric disorders.