Sustained sensorimotor impairments after endothelin-1 induced focal cerebral ischemia (stroke) in aged rats

Environmental enrichment enhanced neurogenesis and behavioral recovery after stroke in aged rats

BACKGROUND AND PURPOSE

Age is identified as a significant prognostic factor for poorer outcome after stroke. However, environmental enrichment (EE) has been reported to promote functional recovery after ischemic stroke. The purpose of this study was to investigate whether environmental enrichment was beneficial to ischemic stroke in aged rats.

METHODS

Aged rats were randomly assigned as control rats, rats subjected to cerebral ischemia, and rats with cerebral ischemia treated with EE for 30 days. Focal cortical ischemia was induced by intracranial injection of endothelin-1 (ET-1). EE housing began one day after focal ischemia and was maintained for the whole experimental period. We used immunofluorescence staining to analyze the neurogenesis in the subventricular zone (SVZ) and TdT-mediated dUTP-biotin nick-end labeling (TUNEL) assay to evaluate apoptosis. The expression of neuronal nuclei, glial fibrillary acidic protein (GFAP) and Iba-1 around the infarcted area were also measured by double immunohistochemistry.

RESULTS

EE enhanced the proliferation of newborn neurons in the SVZ, as well as increased the long-term survival of newborn neurons. EE also exerted effects on inflammation after stroke. Furthermore, EE suppressed apoptosis and improved the motor functions after stroke in the aged rats.

CONCLUSIONS

EE improved post-stroke recovery on the basis of enhancing neurogenesis in aged rats.

Rodent Stroke Models to Study Functional Recovery and Neural Repair

Rodent ischemic stroke models are essential research tools for studying this highly prevalent disease and represent a critical element in the translational pipeline for development of new therapies. The majority of ischemic stroke models have been developed to study the acute phase of the disease and neuroprotective strategies, but a subset of models is better suited for studying stroke recovery. Each model therefore has characteristics that lend itself to certain types of investigations and outcome measures, and it is important to consider both explicit and implicit details when designing experiments that utilize each model. The following chapter briefly summarizes the known aspects of the main rodent stroke models with emphasis on their clinical relevance and suitability for studying recovery and neural repair following stroke.

Ischemic Stroke, Lessons from the Past towards Effective Preclinical Models

Ischemic stroke is a leading cause of death worldwide, mainly in western countries. So far, approved therapies rely on reperfusion of the affected brain area, by intravenous thrombolysis or mechanical thrombectomy. The last approach constitutes a breakthrough in the field, by extending the therapeutic window to 16-24 h after stroke onset and reducing stroke mortality. The combination of pharmacological brain-protective strategies with reperfusion is the future of stroke therapy, aiming to reduce brain cell death and decrease patients' disabilities. Recently, a brain-protective drug-nerinetide-reduced brain infarct and stroke mortality, and improved patients' functional outcomes in clinical trials. The success of new therapies relies on bringing preclinical studies and clinical practice close together, by including a functional outcome assessment similar to clinical reality. In this review, we focused on recent upgrades of in vitro and in vivo stroke models for more accurate and effective evaluation of therapeutic strategies: from spheroids to organoids, in vitro models that include all brain cell types and allow high throughput drug screening, to advancements in in vivo preclinical mouse stroke models to mimic the clinical reality in surgical procedures, postsurgical care, and functional assessment.

Disruption of Sonic Hedgehog Signaling Accelerates Age-Related Neurogenesis Decline and Abolishes Stroke-Induced Neurogenesis and Leads to Increased Anxiety Behavior in Stroke Mice

Sonic Hedgehog (SHH) signaling has a critical role in mediating developmental neurogenesis and has been implicated in adult subventricular (SVZ) neurogenesis. However, the precise role of Smoothened (SMO) receptor-mediated SHH signaling in adult neurogenesis during aging especially in hippocampal subgranular zone (SGZ) neurogenesis remains undefined. Additionally, our previous study showed that stimulation of SHH signaling post-stroke leads to increased neurogenesis and improved behavioral functions after stroke. However, it is not clear whether SHH signaling in neural stem cells (NSCs) is required for stroke-induced neurogenesis and functional recovery post-stroke. In this study, using conditional knockout (cKO) of SHH signaling receptor Smo gene in NSCs, we show a decreased neurogenesis at both SVZ and SGZ in young-adult mice and an accelerated depletion of neurogenic cells in the process of aging suggesting that SHH signaling is critical in maintaining neurogenesis during aging. Behavior studies revealed that compromised neurogenesis in Smo cKO mice leads to increased anxiety/depression-like behaviors without affecting general locomotor function or spatial and fear-related learning. Importantly, we also show that NSCs with a cKO of SHH signaling abolishes stroke-induced neurogenesis in Smo cKO mice. Compared to control mice, Smo cKO mice also show delayed motor function recovery and increased anxiety level after stroke. Our data highlights the essential role of Smo function in regulating adult neurogenesis and emotional behaviors during both aging and CNS injury such as stroke.

The Foot Fault Scoring System to Assess Skilled Walking in Rodents: A Reliability Study

The foot fault scoring system of the ladder rung walking test (LRWT) is used to assess skilled walking in rodents. However, the reliability of the LRWT foot fault score has not been properly addressed. This study was designed to address this issue. Two independent and blinded raters analyzed 20 rats and 20 mice videos. Each video was analyzed twice by the same rater (80 analyses per rater). The intraclass correlation coefficient (ICC) and the Kappa coefficient were employed to check the accuracy of agreement and reliability in the intra- and inter-rater analyses of the LRWT outcomes. Excellent intra- and inter-rater agreements were found for the forelimb, hindlimb, and both limbs combined in rats and mice. The agreement level was also excellent for total crossing time, total time stopped, and the number of stops during the walking path. Rating individual scores in the foot fault score system (0–6) ranged from satisfactory to excellent, in terms of the intraclass correlation indexes. Moreover, we showed that experienced and inexperienced raters can obtain reliable results if supervised training is provided. We concluded that the LRWT is a reliable and useful tool to study skilled walking in rodents and can help researchers address walking-related neurobiological questions.

Hemispheric cortical atrophy and chronic microglial activation following mild focal ischemic stroke in adult male rats

Animal modeling has played an important role in our understanding of the pathobiology of stroke. The vast majority of this research has focused on the acute phase following severe forms of stroke that result in clear behavioral deficits. Human stroke, however, can vary widely in severity and clinical outcome. There is a rapidly building body of work suggesting that milder ischemic insults can precipitate functional impairment, including cognitive decline, that continues through the chronic phase after injury. Here we show that a small infarction localized to the frontal motor cortex of rats following injection of endothelin-1 results in an essentially asymptomatic state based on motor and cognitive testing, and yet produces significant histopathological change including remote atrophy and inflammation that persists up to 1 year. While there is understandably a major focus in stroke research on mitigating the acute consequences of primary infarction, these results point to progressive atrophy and chronic inflammation as additional targets for intervention in the chronic phase after injury. The present rodent model provides an important platform for further work in this area.

Endothelin-1 induced global ischaemia in adult zebrafish: A model with novel entity of stroke research

BACKGROUND

Stroke is a leading cause of death in the general population, and it occurs three times more frequently in diabetic patients, necessitating extensive research into new therapeutics. The reproducibility, similarity, and technical limitations of current animal models are limited.

METHODS

We developed a stroke induction model using pink zebra-Danio-rerio. Diabetes was induced in zebrafish by giving them D-glucose (111 mM) for 14 days, and those with blood glucose levels higher than 100 mg/dl were included in the study. In Zebrafish, an experimental stroke was induced by a single oral administration of Endothelin-1 (ET-1, 3µl/gm). Swimming, behavioural patterns, and cognitive performance were all recorded and analysed using UMA Tracker. The brains were removed for histopathological analysis.

RESULTS

In both the normal and diabetic groups, ET-1 administration resulted in a statistically significant change in swimming pattern and movements. Furthermore, changes in swimming pattern and recovery time were statistically significant in the diabetic ET-1 treatment group. In the neurocognitive assessment paradigm, the behavioural study of ET-1 treated groups revealed a disturbed cognitive profile and locomotor coordination, with an increase in the number of errors and a decrease in total distance travelled. Histopathological analysis of ET-1 treated groups revealed cortical lesions, shrunken neuronal cells, and thrombocytes in spheroid form with disturbed normal architecture of brain tissue when compared to normal control groups in tectum opticum and telencephalon. In terms of stability, reproducibility, and genetic similarity to human stroke, the current experimental model outperforms other available rodent stroke models.

CONCLUSION

The ET-1 induced experimental zebrafish stroke model opens up new avenues for diabetes-related stroke research due to its novelty, reproducibility, and ability to overcome technical errors found in other recent models.

A review of experimental models of focal cerebral ischemia focusing on the middle cerebral artery occlusion model

Cerebral ischemic stroke is a leading cause of death and disability, but current pharmacological therapies are limited in their utility and effectiveness. In vitro and in vivo models of ischemic stroke have been developed which allow us to further elucidate the pathophysiological mechanisms of injury and investigate potential drug targets. In vitro models permit mechanistic investigation of the biochemical and molecular mechanisms of injury but are reductionist and do not mimic the complexity of clinical stroke. In vivo models of ischemic stroke directly replicate the reduction in blood flow and the resulting impact on nervous tissue. The most frequently used in vivo model of ischemic stroke is the intraluminal suture middle cerebral artery occlusion (iMCAO) model, which has been fundamental in revealing various aspects of stroke pathology. However, the iMCAO model produces lesion volumes with large standard deviations even though rigid surgical and data collection protocols are followed. There is a need to refine the MCAO model to reduce variability in the standard outcome measure of lesion volume. The typical approach to produce vessel occlusion is to induce an obstruction at the origin of the middle cerebral artery and reperfusion is reliant on the Circle of Willis (CoW). However, in rodents the CoW is anatomically highly variable which could account for variations in lesion volume. Thus, we developed a refined approach whereby reliance on the CoW for reperfusion was removed. This approach improved reperfusion to the ischemic hemisphere, reduced variability in lesion volume by 30%, and reduced group sizes required to determine an effective treatment response by almost 40%. This refinement involves a methodological adaptation of the original surgical approach which we have shared with the scientific community via publication of a visualised methods article and providing hands-on training to other experimental stroke researchers.

Long-Term Motor Deficit and Diffuse Cortical Atrophy Following Focal Cortical Ischemia in Athymic Rats

Development of new stroke therapies requires animal models that recapitulate the pathophysiological and functional consequences of ischemic brain damage over time-frames relevant to the therapeutic intervention. This is particularly relevant for the rapidly developing area of stem cell therapies, where functional replacement of circuitry will require maturation of transplanted human cells over months. An additional challenge is the establishment of models of ischemia with stable behavioral phenotypes in chronically immune-suppressed animals to allow for long-term survival of human cell grafts. Here we report that microinjection of endothelin-1 into the sensorimotor cortex of athymic rats results in ischemic damage with a sustained deficit in function of the contralateral forepaw that persists for up to 9 months. The histological post-mortem analysis revealed chronic and diffuse atrophy of the ischemic cortical hemisphere that continued to progress over 9 months. Secondary atrophy remote to the primary site of injury and its relationship with long-term cognitive and functional decline is now recognized in human populations. Thus, focal cortical infarction in athymic rats mirrors important pathophysiological and functional features relevant to human stroke, and will be valuable for assessing efficacy of stem cell based therapies.

Stroke Recovery in Rats after 24-Hour-Delayed Intramuscular Neurotrophin-3 Infusion

Objective

Neurotrophin‐3 (NT3) plays a key role in the development and function of locomotor circuits including descending serotonergic and corticospinal tract axons and afferents from muscle and skin. We have previously shown that gene therapy delivery of human NT3 into affected forelimb muscles improves sensorimotor recovery after stroke in adult and elderly rats. Here, to move toward the clinic, we tested the hypothesis that intramuscular infusion of NT3 protein could improve sensorimotor recovery after stroke.

Methods

Rats received unilateral ischemic stroke in sensorimotor cortex. To simulate a clinically feasible time to treatment, 24 hours later rats were randomized to receive NT3 or vehicle by infusion into affected triceps brachii for 4 weeks using implanted catheters and minipumps.

Results

Radiolabeled NT3 crossed from the bloodstream into the brain and spinal cord in rodents with or without strokes. NT3 increased the accuracy of forelimb placement during walking on a horizontal ladder and increased use of the affected arm for lateral support during rearing. NT3 also reversed sensory impairment of the affected wrist. Functional magnetic resonance imaging during stimulation of the affected wrist showed spontaneous recovery of peri‐infarct blood oxygenation level–dependent signal that NT3 did not further enhance. Rather, NT3 induced neuroplasticity of the spared corticospinal and serotonergic pathways.

Interpretation

Our results show that delayed, peripheral infusion of NT3 can improve sensorimotor function after ischemic stroke. Phase I and II clinical trials of NT3 (for constipation and neuropathy) have shown that peripheral high doses are safe and well tolerated, which paves the way for NT3 as a therapy for stroke. ANN NEUROL 2019;85:32–46.

Endothelial cells promote excitatory synaptogenesis and improve ischemia-induced motor deficits in neonatal mice

Brain microvascular endothelial cells (BMEC) are highly complex regulatory cells that communicate with other cells in the neurovascular unit. Cerebral ischemic injury is known to produce detectable synaptic dysfunction. This study aims to investigate whether endothelial cells in the brain regulate postnatal synaptic development and to elucidate their role in functional recovery after ischemia. Here, we found that in vivo engraftment of endothelial cells increased synaptic puncta and excitatory postsynaptic currents in layers 2/3 of the motor cortex. This pro-synaptogenic effect was blocked by the depletion of VEGF in the grafted BMEC. The in vitro results showed that BMEC conditioned medium enhanced spine and synapse formation but conditioned medium without VEGF had no such effects. Moreover, under pathological conditions, transplanted endothelial cells were capable of enhancing angiogenesis and synaptogenesis and improved motor function in the ischemic injury model. Collectively, our findings suggest that endothelial cells promote excitatory synaptogenesis via the paracrine factor VEGF during postnatal development and exert repair functions in hypoxia-ischemic neonatal mice. This study highlights the importance of the endothelium-neuron interaction not only in regulating neuronal development but also in maintaining healthy brain function.

Human neural stem cells dispersed in artificial ECM form cerebral organoids when grafted in vivo

Human neural stem cells (hNSC) derived from induced pluripotent stem cells can be differentiated into neurons that could be used for transplantation to repair brain injury. In this study we dispersed such hNSC in a three-dimensional artificial extracellular matrix (aECM) and compared their differentiation in vitro and following grafting into the sensorimotor cortex (SMC) of postnatal day (P)14 rat pups lesioned by localised injection of endothelin-1 at P12. After 10-43 days of in vitro differentiation, a few cells remained as PAX6⁺ neuroprogenitors but many more resembled post-mitotic neurons expressing doublecortin, β-tubulin and MAP2. These cells remained dispersed throughout the ECM, but with extended long processes for over 50 μm. In vivo, by 1 month post grafting, cells expressing human specific markers instead organised into cerebral organoids: columns of tightly packed PAX6 co-expressing progenitor cells arranged around small tubular lumen in rosettes, with a looser network of cells with processes around the outside co-expressing markers of immature neurons including doublecortin, and CTIP2 characteristic of corticofugal neurons. Host cells also invaded the graft including microglia, astrocytes and endothelial cells forming blood vessels. By 10 weeks post-grafting, the organoids had disappeared and the aECM had started to break down with fewer transplanted cells remaining. In vitro, cerebral organoids form in rotating incubators that force oxygen and nutrients to the centre of the structures. We have shown that cerebral organoids can form in vivo; intrinsic factors may direct their organisation including infiltration by host blood vessels.

A Complete Guide to Using the Endothelin-1 Model of Stroke in Conscious Rats for Acute and Long-Term Recovery Studies

Multiple methods exist to model permanent and transient ischemia under anesthesia in animals, however most human strokes occur while conscious. The use of endothelin-1 as a vasoconstrictor applied to the perivascular surface of the middle cerebral artery is one of the only methods for inducing stroke in conscious animals. Here, we describe standard operating procedures for stereotaxic placement of an ET-1 guide probe above the middle cerebral artery, induction of stroke in conscious rats, predictive outcome scoring during stroke, and neurological behavioral tests that we use to monitor transient and continuing deficits. The inclusion of long term neurological assessment is of particular importance when taking into consideration the effects of stroke on brain remodeling.

The IMPROVE Guidelines (Ischaemia Models: Procedural Refinements Of in Vivo Experiments)

Most in vivo models of ischaemic stroke target the middle cerebral artery and a spectrum of stroke severities, from mild to substantial, can be achieved. This review describes opportunities to improve the in vivo modelling of ischaemic stroke and animal welfare. It provides a number of recommendations to minimise the level of severity in the most common rodent models of middle cerebral artery occlusion, while sustaining or improving the scientific outcomes. The recommendations cover basic requirements pre-surgery, selecting the most appropriate anaesthetic and analgesic regimen, as well as intraoperative and post-operative care. The aim is to provide support for researchers and animal care staff to refine their procedures and practices, and implement small incremental changes to improve the welfare of the animals used and to answer the scientific question under investigation. All recommendations are recapitulated in a summary poster (see supplementary information).

Inhibition of Nkcc1 promotes axonal growth and motor recovery in ischemic rats

Bumetanide is a selective inhibitor of the Na⁺-K⁺-Cl^--co-transporter 1(NKCC1). We studied whether bumetanide could affect axonal growth and behavioral outcome in stroke rats. Adult male Wistar rats were randomly assigned to four groups: sham-operated rats treated with vehicle or bumetanide, and ischemic rats treated with vehicle or bumetanide. Endothelin-1 was used to induce focal cerebral ischemia. Bumetanide administration (i.c.v.) started on postoperative day 7 and continued for 3 weeks. Biotinylated dextran amine (BDA) was injected into the right imotor cortex on postoperative day 14 to trace corticospinal tract (CST) fibers sprouting into the denervated cervical spinal cord. Nogo-A, NKCC1, KCC2 and BDNF in the perilesional cortex and BDA, PSD-95 and vGlut1 in the denervated spinal cord were measured by immunohistochemistry and/or Western blot. Behavioral outcome of rats was assessed by the beam walking and cylinder tests. The total length of CST fibers sprouting into the denervated cervical spinal cord significantly increased after stroke and bumetanide further increased this sprouting. Bumetanide treatment also decreased the expressions of NKCC1 and Nogo-A, increased the expressions of KCC2 and BDNF in the perilesional cortex and enhanced the synaptic plasticity in the denervated cervical spinal cord after cerebral ischemia. The behavioral performance of ischemic rats was significantly improved by bumetanide. In conclusion, bumetanide promoted post-stroke axonal sprouting together accompanied by an improved behavioral outcome possibly through restoring and maintaining neuronal chloride homeostasis and creating a recovery-promoting microenvironment by overcoming the axonal growth inhibition encountered after cerebral ischemia in rats.

Evolution of ischemic damage and behavioural deficit over 6 months after MCAo in the rat: Selecting the optimal outcomes and statistical power for multi-centre preclinical trials

Key disparities between the timing and methods of assessment in animal stroke studies and clinical trial may be part of the reason for the failure to translate promising findings. This study investigates the development of ischemic damage after thread occlusion MCAo in the rat, using histological and behavioural outcomes. Using the adhesive removal test we investigate the longevity of behavioural deficit after ischemic stroke in rats, and examine the practicality of using such measures as the primary outcome for future studies. Ischemic stroke was induced in 132 Spontaneously Hypertensive Rats which were assessed for behavioural and histological deficits at 1, 3, 7, 14, 21, 28 days, 12 and 24 weeks (n>11 per timepoint). The basic behavioural score confirmed induction of stroke, with deficits specific to stroke animals. Within 7 days, these deficits resolved in 50% of animals. The adhesive removal test revealed contralateral neglect for up to 6 months following stroke. Sample size calculations to facilitate the use of this test as the primary experimental outcome resulted in cohort sizes much larger than are the norm for experimental studies. Histological damage progressed from a necrotic infarct to a hypercellular area that cleared to leave a fluid filled cavity. Whilst absolute volume of damage changed over time, when corrected for changes in hemispheric volume, an equivalent area of damage was lost at all timepoints. Using behavioural measures at chronic timepoints presents significant challenges to the basic science community in terms of the large number of animals required and the practicalities associated with this. Multicentre preclinical randomised controlled trials as advocated by the MultiPART consortium may be the only practical way to deal with this issue.

Establishment and characterization of porcine focal cerebral ischemic model induced by endothelin-1

BACKGROUND AND PURPOSE

Due to well-developed Circle of Willis in pigs, it is technically challenging to make persistent focal ischemic stroke based on occlusion of cerebral arteries. Endothelin-1 could cause a focal lesion by forcing transient but strong vasoconstriction in the circumscribed injected area. Its use in porcine stroke model has drawn attention lately. However, all the porcine endothelin-1 induced models were euthanized soon after surgery. Whether the brain lesion is persistent, and whether they could cause neurological deficit are not known. This research aims to provide a more detailed characterization of endothelin-1 induced porcine cerebral ischemic model by evaluating the change of neurological function and the brain lesion monitored by MRI of the pigs.

METHODS

Danish Domestic pigs were randomly divided into two groups: a group receiving endothelin-1 (ET-1 group, n=6) and a sham group (n=6). After the fronto-temporal craniotomy, pigs in the ET-1 group received 200μl endothelin-1 injected within a cortical area of one cm²; pigs in the sham group received only saline injections. Neurological deficit evaluation and MRI scanning were done 24h and 72h after operation. Afterwards, hematoxylin and eosin staining was conducted to detect the morphological characteristics of the damaged brain tissue.

RESULTS

The average performance score in the pigs of the ET-1 group was 9.67±1.03 and 9.00±1.26 respectively, at 24h and 72h after surgery, which was significantly higher than that of the pigs in sham group. The brain lesion percentage detected by MRI was 12.26±0.60%, and 10.33±0.51% respectively, at 24h and 72h after surgery in the ET-1 group. Microscopy showed extended pyknotic neuronal perikarya in neurons located in the ischemic area.

CONCLUSIONS

The endothelin-1 induced porcine cerebral ischemic model is technically easier, and able to create cerebral ischemia severe enough to cause a functional neurological deficit as well as observable lesions on MRI. It is a suitable model for long-term cerebral ischemia research.

Bone-marrow-derived mesenchymal stem cells attenuate cognitive deficits in an endothelin-1 rat model of stroke

PURPOSE

Stroke is the third leading cause of death and permanent disability in the United States, often producing long-term cognitive impairments, which are not easily recapitulated in animal models. The goals of this study were to assess whether: (1) the endothelin-1 (ET-1) model of chronic stroke produced discernable cognitive deficits; (2) a spatial operant reversal task (SORT) would accurately measure memory deficits in this model; and (3) bone-marrow-derived mesenchymal stem cells (BMMSCs) could reduce any observed deficits.

METHODS

Rats were given unilateral intracerebral injections of vehicle or ET-1, a stroke-inducing agent, near the middle cerebral artery. Seven days later, they were given intrastriatal injections of BMMSCs or vehicle, near the ischemic penumbra. The cognitive abilities of the rats were assessed on a novel SORT, which was designed to efficiently distinguish cognitive deficits from potential motoric confounds.

RESULTS

Rats given ET-1 had significantly more cognitive errors at six weeks post-stroke on the SORT, and that these deficits were attenuated by BMMSC transplants.

CONCLUSIONS

These findings indicate that: (1) the ET-1 model produces chronic cognitive deficits; (2) the SORT efficiently measures cognitive deficits that are not confounded by motoric impairment; and (3) BMMSCs may be a viable treatment for stroke-induced cognitive dysfunction.

Bumetanide promotes neural precursor cell regeneration and dendritic development in the hippocampal dentate gyrus in the chronic stage of cerebral ischemia

Bumetanide has been shown to lessen cerebral edema and reduce the infarct area in the acute stage of cerebral ischemia. Few studies focus on the effects of bumetanide on neuroprotection and neurogenesis in the chronic stage of cerebral ischemia. We established a rat model of cerebral ischemia by injecting endothelin-1 in the left cortical motor area and left corpus striatum. Seven days later, bumetanide 200 µg/kg/day was injected into the lateral ventricle for 21 consecutive days with a mini-osmotic pump. Results demonstrated that the number of neuroblasts cells and the total length of dendrites increased, escape latency reduced, and the number of platform crossings increased in the rat hippocampal dentate gyrus in the chronic stage of cerebral ischemia. These findings suggest that bumetanide promoted neural precursor cell regeneration, dendritic development and the recovery of cognitive function, and protected brain tissue in the chronic stage of ischemia.

Analysis of longitudinal data from animals with missing values using SPSS

Testing of therapies for disease or injury often involves the analysis of longitudinal data from animals. Modern analytical methods have advantages over conventional methods (particularly when some data are missing), yet they are not used widely by preclinical researchers. Here we provide an easy-to-use protocol for the analysis of longitudinal data from animals, and we present a click-by-click guide for performing suitable analyses using the statistical package IBM SPSS Statistics software (SPSS). We guide readers through the analysis of a real-life data set obtained when testing a therapy for brain injury (stroke) in elderly rats. If a few data points are missing, as in this example data set (for example, because of animal dropout), repeated-measures analysis of covariance may fail to detect a treatment effect. An alternative analysis method, such as the use of linear models (with various covariance structures), and analysis using restricted maximum likelihood estimation (to include all available data) can be used to better detect treatment effects. This protocol takes 2 h to carry out.

The efficacy of the ketogenic diet on motor functions in Parkinson's disease: A rat model

BACKGROUND

The ketogenic diet (KD), high in fat and low in carbohydrate and protein, provides sufficient protein but insufficient carbohydrates for all the metabolic needs of the body. KD has been known as a therapeutic manner intractable epilepsy. In recent years, the effectiveness of KD drew attention to the treatment of some other disorders such as Parkinson's disease (PD). This study has evaluated the efficacy of KD on motor function in Parkinsonian model of rat and compared it with pramipexole.

METHODS

A total of 56 male Wistar rats weighing 200-240 g between 12 and 14 weeks of age were randomized in seven 8-rat groups as follows: Control group; sham-operated group; KD group; Parkinsonian control group; KD-Parkinsonian group; pramipexole-Parkinsonian group; and KD-pramipexole-Parkinsonian group. The results of bar test, beam traversal task test, and cylinder task test were compared between the groups.

RESULTS

The mean number of ketone bodies had increased significantly in the rats blood after KD. Regarding the results of the triad tests, no statistically significant difference was found between the controls and the sham-operated group. Among the Parkinsonian rats, better results were found in KD groups compared to the non-KD group. The KD enhanced the effect of pramipexole for motor function but did not reach a statistically significant level.

CONCLUSION

The KD reinforced the motor function in Parkinsonian rats in our study. When the diet was combined with pramipexole, the effectiveness of the drug increased in enhancing motor function.

Chloride Co-transporter NKCC1 Inhibitor Bumetanide Enhances Neurogenesis and Behavioral Recovery in Rats After Experimental Stroke

Bumetanide, a selective Na⁺-K⁺-Cl^--co-transporter inhibitor, is widely used in clinical practice as a loop diuretic. In addition, bumetanide has been reported to attenuate ischemia-induced cerebral edema and reduce neuronal injury. This study examined whether bumetanide could influence neurogenesis and behavioral recovery in rats after experimentally induced stroke. Adult male Wistar rats were randomly assigned to four groups: sham, sham treated with bumetanide, ischemia, and ischemia treated with bumetanide. Focal cerebral ischemia was induced by injection of endothelin-1. Bumetanide (0.2 mg/kg/day) was infused into the lateral ventricle with drug administration being initiated 1 week after ischemia and continued for 3 weeks. Behavioral impairment and recovery were evaluated by tapered/ledged beam-walking test on post-stroke days 28. Then, the rats were perfused for BrdU/DCX (neuroblast marker), BrdU/NeuN (neuronal marker), BrdU/GFAP (astrocyte marker), and BrdU/Iba-1 (microglia marker) immunohistochemistry. The numbers of neuroblasts in the subventricular zone (SVZ) were significantly increased after the experimentally induced stroke. Bumetanide treatment increased migration of neuroblasts in the SVZ towards the infarct area, enhanced long-term survival of newborn neurons, and improved sensorimotor recovery, but it did not exert any effects on inflammation. In conclusion, our results demonstrated that chronic bumetanide treatment enhances neurogenesis and behavioral recovery after experimentally induced stroke in rats.

Neurological function following cerebral ischemia/reperfusion is improved by the Ruyi Zhenbao pill in a rats

The present study aimed to investigate the effect and underlying mechanisms of the Ruyi Zhenbao pill on neurological function following cerebral ischemia/reperfusion in rats. Male Sprague-Dawley rats underwent middle cerebral artery occlusion following reperfusion. The rats received intragastrically either sodium carboxymethyl cellulose (control and model groups) or Ruyi Zhenbao pill at doses of 0.2, 0.4 or 0.8 g/kg. Neurological function was assessed by cylinder, adhesive and beam-walking tests after 14-day Ruyi Zhenbao pill treatment. Neurogenesis and angiogenesis were detected using immunofluorescence staining. The expression levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) were determined by enzyme-linked immunosorbent assays. Treatment with 0.4 and 0.8 g/kg Ruyi Zhenbao for 14 days significantly improved neurological function, and increased the number of von Willebrand Factor- and neuronal nuclear antigen-positive cells in the ischemic hemisphere of rats. Ruyi Zhenbao pill treatment also significantly enhanced the expression levels of BDNF, NGF and VEGF in the ischemic hemisphere. The results demonstrated that the Ruyi Zhenbao pill improved neurological function following ischemia in rats. The mechanisms of the Ruyi Zhenbao pill are associated with increasing the expression levels of BDNF, NGF and VEGF, and subsequently promoting neurogenesis and angiogenesis in the ischemic zone.

Delayed intramuscular human neurotrophin-3 improves recovery in adult and elderly rats after stroke

There is an urgent need for a therapy that reverses disability after stroke when initiated in a time frame suitable for the majority of new victims. We show here that intramuscular delivery of neurotrophin-3 (NT3, encoded by NTF3) can induce sensorimotor recovery when treatment is initiated 24 h after stroke. Specifically, in two randomized, blinded preclinical trials, we show improved sensory and locomotor function in adult (6 months) and elderly (18 months) rats treated 24 h following cortical ischaemic stroke with human NT3 delivered using a clinically approved serotype of adeno-associated viral vector (AAV1). Importantly, AAV1-hNT3 was given in a clinically-feasible timeframe using a straightforward, targeted route (injections into disabled forelimb muscles). Magnetic resonance imaging and histology showed that recovery was not due to neuroprotection, as expected given the delayed treatment. Rather, treatment caused corticospinal axons from the less affected hemisphere to sprout in the spinal cord. This treatment is the first gene therapy that reverses disability after stroke when administered intramuscularly in an elderly body. Importantly, phase I and II clinical trials by others show that repeated, peripherally administered high doses of recombinant NT3 are safe and well tolerated in humans with other conditions. This paves the way for NT3 as a therapy for stroke.

Fluoxetine enhanced neurogenesis is not translated to functional outcome in stroke rats

Fluoxetine is widely used in clinical practice. It regulates hippocampal neurogenesis, however, the effect of fluoxetine on neurogenesis in the subventricular zone (SVZ) remains controversial. We aimed to study the effect of fluoxetine on neurogenesis in the SVZ and subgranular zone (SGZ) of dentate gyrus (DG) in relation to behavioral recovery after stroke in rats. Adult male Wistar rats were randomly assigned to four groups: sham-operated rats, sham-operated rats treated with fluoxetine, rats subjected to cerebral ischemia, and rats with ischemia treated with fluoxetine. Fluoxetine was orally administrated starting 1 week after ischemia, with a dose of 16mg/kg/day for 3 weeks. Focal cerebral ischemia was induced by intracranial injection of vasoconstrictive peptide endothelin-1(ET-1). Behavioral recovery was evaluated on post-stroke days 29-31 after which the survival rate and fate of proliferating cells in the SVZ and DG were measured by immunohistochemistry. The production of neuroblasts in both the SVZ and DG was significantly increased after stroke. Chronic post-stroke fluoxetine treatment increased the dendritic complexity of newborn dentate granule cells. However, fluoxetine treatment did not influence the survival or differentiation of newly generated cells. Neither fluoxetine treatment improved sensorimotor recovery following focal cerebral ischemia.

Age-dependent reorganization of peri-infarct "premotor" cortex with task-specific rehabilitative training in mice

BACKGROUND

The incidence of stroke in adulthood increases with advancing age, but there is little understanding of how poststroke treatment should be tailored by age.

OBJECTIVE

The goal of this study was to determine if age and task specificity of rehabilitative training affect behavioral improvement and motor cortical organization after stroke.

METHODS

Young and aged mice were trained to proficiency on the Pasta Matrix Reaching Task prior to lesion induction in primary motor cortex with endothelin-1. After a short recovery period, mice received 9 weeks of rehabilitative training on either the previously learned task (Pasta Matrix Reaching), a different reaching task (Tray Reaching), or no training. To determine the extent of relearning, mice were tested once weekly on the Pasta Matrix Reaching Task. Mice then underwent intracortical microstimulation mapping to resolve the remaining forelimb movement representations in perilesion motor cortex.

RESULTS

Although aged mice had significantly larger lesions compared with young mice, Pasta Matrix Reaching served as effective rehabilitative training for both age-groups. Young animals also showed improvement after Tray Reaching. Behavioral improvement in young mice was associated with an expansion of the rostral forelimb area ("premotor" cortex), but we failed to see reorganization in the aged brain, despite similar behavioral improvements.

CONCLUSIONS

Our results indicate that reorganization of motor cortex may be limited by either aging or greater tissue damage, but the capacity to improve motor function via task-specific rehabilitative training continues to be well maintained in aged animals.

Time course of neuronal death following endothelin-1 induced focal ischemia in rats

BACKGROUND

Endothelin-1 (ET-1) induced focal ischemia is increasingly being used as a preclinical model of stroke. Here, we described for the first time, the time course of neuronal death and infarct evolution during the first 7 days following ischemia.

NEW METHOD

We used hematoxylin and eosin (H&E) staining to evaluate infarct progression and Fluoro-Jade C (FJC) to quantify neuronal degeneration at 24, 48, 72h and 7 days after ET-1 injection to the forelimb motor cortex in Sprague-Dawley rats.

RESULTS

We found that infarct volume and neuronal degeneration are maximal at 24h post-stroke. Neuronal degeneration is also significantly reduced within 7 days of stroke induction.

COMPARISON WITH EXISTING METHOD

This study is the first to provide a direct evaluation of both infarct volume evolution and neuronal death time course following ET-1 induced focal ischemia in the forelimb motor cortex.

CONCLUSION

This study describes the short-term time course of neuronal death and brain injury in the ET-1 stroke model, which provides a significant reference when determining the appropriate time to commence neuroprotective or recovery promoting strategies.

Unilateral pyramidotomy of the corticospinal tract in rats for assessment of neuroplasticity-inducing therapies

The corticospinal tract (CST) can be completely severed unilaterally in the medullary pyramids of the rodent brainstem. The CST is a motor tract that has great importance for distal muscle control in humans and, to a lesser extent, in rodents. A unilateral cut of one pyramid results in loss of CST innervation of the spinal cord mainly on the contralateral side of the spinal cord leading to transient motor disability in the forelimbs and sustained loss of dexterity. Ipsilateral projections of the corticospinal tract are minor. We have refined our surgical method to increase the chances of lesion completeness. We describe postsurgical care. Deficits on the Montoya staircase pellet reaching test and the horizontal ladder test shown here are detected up to 8 weeks postinjury. Deficits on the cylinder rearing test are only detected transiently. Therefore, the cylinder test may only be suitable for detection of short term recovery. We show how, electrophysiologically and anatomically, one may assess lesions and plastic changes. We also describe how to analyse fibers from the uninjured CST sprouting across the midline into the deprived areas. It is challenging to obtain >90% complete lesions consistently due to the proximity to the basilar artery in the medulla oblongata and survival rates can be low. Alternative surgical approaches and behavioural testing are described in this protocol. The pyramidotomy model is a good tool for assessing neuroplasticity-inducing treatments, which increase sprouting of intact fibers after injury.

Stem cell therapies in preclinical models of stroke associated with aging

Stroke has limited treatment options, demanding a vigorous search for new therapeutic strategies. Initial enthusiasm to stimulate restorative processes in the ischemic brain by means of cell-based therapies has meanwhile converted into a more balanced view recognizing impediments related to unfavorable environments that are in part related to aging processes. Since stroke afflicts mostly the elderly, it is highly desirable and clinically important to test the efficacy of cell therapies in aged brain microenvironments. Although widely believed to be refractory to regeneration, recent studies using both neural precursor cells and bone marrow-derived mesenchymal stem cells for stroke therapy suggest that the aged rat brain is not refractory to cell-based therapy, and that it also supports plasticity and remodeling. Yet, important differences exist in the aged compared with young brain, i.e., the accelerated progression of ischemic injury to brain infarction, the reduced rate of endogenous neurogenesis and the delayed initiation of neurological recovery. Pitfalls in the development of cell-based therapies may also be related to age-associated comorbidities, e.g., diabetes or hyperlipidemia, which may result in maladaptive or compromised brain remodeling, respectively. These age-related aspects should be carefully considered in the clinical translation of restorative therapies.

Loss of motor coordination in an aging mouse model

With age, there is an increase in motor deficits that leads to an increased incidence of slips and falls. As the elderly population continues to grow, there is a need for aging models and research that focus on behavioral deficits that occur with normal, non-diseased aging. The present study was designed to examine the appropriateness of C57Bl/6 male mice as aging animal models using the challenging beam and cylinder tests to measure motor coordination and spontaneous activity, respectively. Using young (2-4 mo), middle-aged (10-12 mo), and aged (22-24 mo) mice, we observed that aged C57Bl/6 male mice make more errors on the challenging beam task and take fewer hind limb steps as compared to young and middle-aged mice. Body weight and food intake were also measured to determine if these parameters were confounding factors in the interpretation of the behavioral data. Increases in body weight and food consumption were not observed in the oldest group that made the most errors. Together these data indicate that aged C57BL/6 mice display age-related motor deficits similar to those seen in humans and are an appropriate model of motor deficits that occur with age.

Experimental models of brain ischemia: a review of techniques, magnetic resonance imaging, and investigational cell-based therapies

Stroke continues to be a significant cause of death and disability worldwide. Although major advances have been made in the past decades in prevention, treatment, and rehabilitation, enormous challenges remain in the way of translating new therapeutic approaches from bench to bedside. Thrombolysis, while routinely used for ischemic stroke, is only a viable option within a narrow time window. Recently, progress in stem cell biology has opened up avenues to therapeutic strategies aimed at supporting and replacing neural cells in infarcted areas. Realistic experimental animal models are crucial to understand the mechanisms of neuronal survival following ischemic brain injury and to develop therapeutic interventions. Current studies on experimental stroke therapies evaluate the efficiency of neuroprotective agents and cell-based approaches using primarily rodent models of permanent or transient focal cerebral ischemia. In parallel, advancements in imaging techniques permit better mapping of the spatial-temporal evolution of the lesioned cortex and its functional responses. This review provides a condensed conceptual review of the state of the art of this field, from models and magnetic resonance imaging techniques through to stem cell therapies.

Age-dependence of sensorimotor and cerebral electroencephalographic asymmetry in rats subjected to unilateral cerebrovascular stroke

BACKGROUND

The human population mostly affected by stroke is more than 65 years old. This study was designed to meet the recommendation that models of cerebral ischemia in aged animals are more relevant to the clinical setting than young animal models. Until now the majority of the pre-clinical studies examining age effects on stroke outcomes have used rats of old age. Considering the increasing incidence of stroke among younger than old human population, new translational approaches in animal models are needed to match the rejuvenation of stroke. A better knowledge of alterations in stroke outcomes in middle-aged rats has important preventive and management implications providing clues for future investigations on effects of various neuroprotective and neurorestorative drugs against cerebrovascular accidents that may occur before late senescence.

METHODS

We evaluated the impact of transient focal ischemia, induced by intracerebral unilateral infusion of endothelin-1 (Et-1) near the middle cerebral artery of conscious rats, on volume of brain damage and asymmetry in behavioral and electroencephalographic (EEG) output measures in middle-aged (11-12 month-old) rats.

RESULTS

We did not find any age-dependent difference in the volume of ischemic brain damage three days after Et-1 infusion. However, age was an important determinant of neurological and EEG outcomes after stroke. Middle-aged ischemic rats had more impaired somatosensory functions of the contralateral part of the body than young ischemic rats and thus, had greater left-right reflex/sensorimotor asymmetry. Interhemispheric EEG asymmetry was more evident in middle-aged than in young ischemic rats, and this could tentatively explain the behavioral asymmetry.

CONCLUSIONS

With a multiparametric approach, we have validated the endothelin model of ischemia in middle-aged rats. The results provide clues for future studies on mechanisms underlying plasticity after brain damage and motivate investigations of novel neuroprotective strategies against cerebrovascular accidents that may occur before late senescence.

Neuroprotective efficacy of subcutaneous insulin-like growth factor-I administration in normotensive and hypertensive rats with an ischemic stroke

The aim of this study was to test the insulin-like growth factor-I (IGF-I) as a neuroprotective agent in a rat model for ischemic stroke and to compare its neuroprotective effects in conscious normotensive and spontaneously hypertensive rats. The effects of subcutaneous IGF-I injection were investigated in both rat strains using the endothelin-1 rat model for ischemic stroke. Motor-sensory functions were measured using the Neurological Deficit Score. Infarct size was assessed by Cresyl Violet staining. Subcutaneous administration of IGF-I resulted in significantly reduced infarct volumes and an increase in motor-sensory functions in normotensive rats. In these rats, IGF-I did not modulate blood flow in the striatum and had no effect on the activation of astrocytes as assessed by GFAP staining. In hypertensive rats, the protective effects of IGF-I were smaller and not always significant. Furthermore, IGF-I significantly reduced microglial activation in the cortex of hypertensive rats, but not in normotensive rats. More detailed studies are required to find out whether the reduction by IGF-I of microglial activation contributes to an impairment IGF-I treatment efficacy. Indeed, we have shown before that microglia in hypertensive rats have different properties compared to those in control rats, as they exhibit a reduced responsiveness to ischemic stroke and lipopolysaccharide.

Constraint-Induced Movement Therapy Overcomes the Intrinsic Axonal Growth–Inhibitory Signals in Stroke Rats

Background and Purpose—

Constraint-induced movement therapy (CIMT) improves functional outcome in patients with stroke possibly through structural plasticity. We hypothesized that CIMT could enhance axonal growth by overcoming the intrinsic growth–inhibitory signals, leading eventually to improved behavioral performance in stroke rats.

Methods—

Focal cerebral ischemia was induced by intracerebral injection of endothelin-1. Adult Wistar rats were divided into a sham-operated group, an ischemic group, and an ischemic group treated with CIMT. CIMT started at postoperative day 7 and continued for 3 weeks. Biotinylated dextran amine was injected into the contralateral sensorimotor cortex at postoperative day 14 to trace crossing axons at the cervical spinal cord. The expressions of Nogo-A, Nogo receptor, RhoA, and Rho-associated kinase in the peri-infarct cortex, and the expressions of biotinylated dextran amine, growth associated protein-43, synaptophysin, vGlut1, and postsynaptic density-95 in the denervated spinal cord were measured by immunohistochemistry and Western blots. Behavioral recovery was analyzed at postoperative days 29 to 32.

Results—

Infarct volumes were not different between groups after stroke. CIMT significantly increased the length and the number of midline crossings of contralateral corticospinal axons to the denervated cervical spinal cord. CIMT significantly decreased the expressions of Nogo-A/Nogo receptor and RhoA/Rho-associated kinase in the peri-infarct cortex, and increased the expressions of growth associated protein-43, synaptophysin, vGlut1, and postsynaptic density-95 in the denervated cervical spinal cord. Behavioral performances assessed by the beam-walking test and the water maze test were improved significantly by CIMT.

Conclusions—

CIMT promoted poststroke synaptic plasticity and axonal growth at least partially by overcoming the intrinsic growth–inhibitory signaling, leading to improved behavioral outcome.

Accumulation of micron sized iron oxide particles in endothelin-1 induced focal cortical ischemia in rats is independent of cell migration

PURPOSE

Endogenous labeling of stem/ progenitor cells via intracerebroventricular injection of micron-sized particles of iron oxide (MPIOs) has become standard methodology for MRI of adult neurogenesis. While this method is well characterized in the naïve rodent brain, it has not been fully investigated in disease models. Here, we describe methodological challenges that can confound data analysis when this technique is applied to a rat model of stroke, the endothelin-1 model of focal cortical ischemia.

METHODS

We intended to track endogenous neuroblast migration from the subventricular zone to the stroke area using previously described methods for in vivo labeling of endogenous neuroblasts with MPIOs and following migration with high resolution MRI.

RESULTS

MPIOs accumulation in stroke regions of endothelin-1-treated brains involves two dynamic steps: an initial rapid cell independent mechanism, followed by slower MPIOs accumulation. While the latter may in part be attributable to cell dependent delivery of the particles, the cell independent mechanism complicates the interpretation of the data. Strategies aimed at prelabeling the stem cell niche reduced cell independent MPIOs accumulation, but failed to abolish it.

CONCLUSION

We conclude that MRI-based neural stem/progenitor cell tracking via direct injection of MPIOs into the lateral and third ventricles, requires significant validation in models of brain disease/trauma.

The omega-3 fatty acid eicosapentaenoic acid accelerates disease progression in a model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurodegenerative disease characterised by loss of motor neurons that currently has no cure. Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), have many health benefits including neuroprotective and myoprotective potential. We tested the hypothesis that a high level of dietary EPA could exert beneficial effects in ALS. The dietary exposure to EPA (300 mg/kg/day) in a well-established mouse model of ALS expressing the G93A superoxide dismutase 1 (SOD1) mutation was initiated at a pre-symptomatic or symptomatic stage, and the disease progression was monitored until the end stage. Daily dietary EPA exposure initiated at the disease onset did not significantly alter disease presentation and progression. In contrast, EPA treatment initiated at the pre-symptomatic stage induced a significantly shorter lifespan. In a separate group of animals sacrificed before the end stage, the tissue analysis showed that the vacuolisation detected in G93A-SOD1 mice was significantly increased by exposure to EPA. Although EPA did not alter motor neurone loss, EPA reversed the significant increase in activated microglia and the astrocytic activation seen in G93A-SOD1 mice. The microglia in the spinal cord of G93A-SOD1 mice treated with EPA showed a significant increase in 4-hydroxy-2-hexenal, a highly toxic aldehydic oxidation product of omega-3 fatty acids. These data show that dietary EPA supplementation in ALS has the potential to worsen the condition and accelerate the disease progression. This suggests that great caution should be exerted when considering dietary omega-3 fatty acid supplements in ALS patients.

Animal models of post-ischemic forced use rehabilitation: methods, considerations, and limitations

Many survivors of stroke experience arm impairments, which can severely impact their quality of life. Forcing use of the impaired arm appears to improve functional recovery in post-stroke hemiplegic patients, however the mechanisms underlying improved recovery remain unclear. Animal models of post-stroke rehabilitation could prove critical to investigating such mechanisms, however modeling forced use in animals has proven challenging. Potential problems associated with reported experimental models include variability between stroke methods, rehabilitation paradigms, and reported outcome measures. Herein, we provide an overview of commonly used stroke models, including advantages and disadvantages of each with respect to studying rehabilitation. We then review various forced use rehabilitation paradigms, and highlight potential difficulties and translational problems. Lastly, we discuss the variety of functional outcome measures described by experimental researchers. To conclude, we outline ongoing challenges faced by researchers, and the importance of translational communication. Many stroke patients rely critically on rehabilitation of post-stroke impairments, and continued effort toward progression of rehabilitative techniques is warranted to ensure best possible treatment of the devastating effects of stroke.

A novel approach to induction and rehabilitation of deficits in forelimb function in a rat model of ischemic stroke

AIM

Constraint-induced movement therapy (CIMT), which forces use of the impaired arm following unilateral stroke, promotes functional recovery in the clinic but animal models of CIMT have yielded mixed results. The aim of this study is to develop a refined endothelin-1 (ET-1) model of focal ischemic injury in rats that resulted in reproducible, well-defined lesions and reliable upper extremity impairments, and to determine if an appetitively motivated form of rehabilitation (voluntary forced use movement therapy; FUMT) would accelerate post-ischemic motor recovery.

METHODS

Male Sprague Dawley rats (3 months old) were given multiple intracerebral microinjections of ET-1 into the sensorimotor cortex and dorsolateral striatum. Sham-operated rats received the same surgical procedure up to but not including the drill holes on the skull. Functional deficits were assessed using two tests of forelimb placing, a forelimb postural reflex test, a forelimb asymmetry test, and a horizontal ladder test. In a separate experiment ET-1 stroke rats were subjected to daily rehabilitation with FUMT or with a control therapy beginning on post-surgery d 5. Performance and post-mortem analysis of lesion volume and regional BDNF expression were measured.

RESULTS

Following microinjections of ET-1 animals exhibited significant deficits in contralateral forelimb function on a variety of tests compared with the sham group. These deficits persisted for up to 20 d with no mortality and were associated with consistent lesion volumes. FUMT therapy resulted in a modest but significantly accelerated recovery in the forelimb function as compared with the control therapy, but did not affect lesion size or BDNF expression in the ipsilesional hemisphere.

CONCLUSION

We conclude that refined ET-1 microinjection protocols and forcing use of the impaired forelimb in an appetitively motivated paradigm may prove useful in developing strategies to study post-ischemic rehabilitation and neuroplasticity.

Low-dose GYKI-52466: prophylactic preconditioning confers long-term neuroprotection and functional recovery following hypoxic-ischaemic brain injury

Experimental preconditioning provides beneficial outcomes in conditions such as cardiac surgery, brain surgery and stroke. Here we evaluated the protective effects of low-dose subcutaneous GYKI-52466 preconditioning in a rat model of hypoxic-ischaemic (HI) brain injury. Male Sprague-Dawley rats (postnatal day 26) were administered saline or GYKI-52466 (GYKI; 3-mg/kg, 90 min; 1-mg/kg, twice in 120 min; or 0.5-mg/kg, thrice in 180 min) prior to left common carotid artery occlusion. Animals were allowed to recover for 2h, and then placed in a hypoxia chamber (8% O₂/92% N₂; 33 ± 1°C) for 1h. A sham surgery group received saline without HI. Seizure activity was scored during hypoxia and sensorimotor tests performed before surgery and at 1, 7, 14 and 90 days post-HI. On days 14 and 90 brains were fixed and sectioned for the assessment of infarct size and ventricular enlargement. Low-dose GYKI-52466 preconditioning significantly reduced infarct volume and ventricular enlargement relative to saline-treated controls at day 14 after HI. On day 90, tissue loss was significantly reduced by GYKI 3-mg/kg compared to saline. Foot-faults, paw use asymmetry, and postural reflex scores were significantly improved in all GYKI treatment groups. Our results show that GYKI-52466 is effective at doses well-below, and at pre-administration intervals well-beyond previous studies, and suggest that a classical blockade of ionotropic AMPA receptors does not underlie its neuroprotective effects. Low-dose GYKI-52466 preconditioning represents a novel, prophylactic strategy for neuroprotection in a field almost devoid of effective pharmaceuticals.

Delayed treatment with chondroitinase ABC promotes sensorimotor recovery and plasticity after stroke in aged rats

Stroke is the dominant cause of sensorimotor disability that primarily affects the elderly. We now show that neuroplasticity and functional recovery after stroke is constrained by inhibitory chondroitin sulphates. In two blinded, randomized preclinical trials, degradation of chondroitin sulphate using chondroitinase ABC reactivated neuroplasticity and promoted sensorimotor recovery after stroke in elderly rats. Three days after stroke, chondroitinase ABC was microinjected into the cervical spinal cord to induce localized plasticity of forelimb sensorimotor spinal circuitry. Chondroitinase ABC effectively removed chondroitin sulphate from the extracellular matrix and perineuronal nets. Three different tests of sensorimotor function showed that chondroitinase ABC promoted recovery of forelimb function. Anterograde and retrograde tracing showed that chondroitinase ABC also induced sprouting of the contralesional corticospinal tract in the aged treated hemicord. Chondroitinase ABC did not neuroprotect the peri-infarct region. We show for the first time delayed chondroitinase ABC treatment promotes neuroanatomical and functional recovery after focal ischaemic stroke in an elderly nervous system.

Aging-related kidney damage is associated with a decrease in klotho expression and an increase in superoxide production

The purpose of this study was to determine changes in klotho, endothelin (ET) receptors, and superoxide production in kidneys of aged rats and whether these changes are exacerbated in aged rats with cognitive impairment. Twenty aged rats (male, 27 months) were divided into an Old Impaired group (n=9) and an Old Intact group (n=11) according to a cognitive function test. A group of 12-month-old rats (n=10) was used as a Young Intact group. Serum creatinine was increased significantly in the Old Impaired group, suggesting impaired renal function. Aged rats showed glomerulosclerosis and tubulointerstitialfibrosis. These pathological changes were markedly aggravated in the old cognitively impaired than in the old cognitively intact animals. Notably, aged rats demonstrated a significant decrease in klotho protein expression in renal cortex and medulla. Protein expression of IL-6, Nox2, ETa receptors and superoxide production were increased whereas mitochondrial SOD (MnSOD) and ETb receptors expression were decreased in kidneys of the aged rats. Interestingly, these changes were more pronounced in the old impaired than in the old intact rats. In conclusion, the aging-related kidney damage was exacerbated in aged rats with cognitive impairment. Klotho, ETB, and MnSOD were downregulated but ETa, IL-6, Nox2, and superoxide production were upregulated in the aging-related kidney damage. These changes were more pronounced in rats with cognitive impairment.

Rehabilitative training following unilateral pyramidotomy in adult rats improves forelimb function in a non-task-specific way

Spontaneous functional recovery following injury to the adult central nervous system can be enhanced with increased and focused activity, either through altered behaviour (skill learning, exercise or training) or by artificial stimulation (magnetic or electrical). In terms of training, the choice of paradigm plays a key role in the recovered behaviour. Here we show that task-specific training leads to improved forelimb function that can be translated to a novel forelimb task. Adult Long-Evans rats received a unilateral pyramidotomy and we studied the effects of different post-lesion training paradigms for their ability to recover function in the impaired limb. We trained rats on either the single pellet grasping or the horizontal ladder task. Rats were tested on both tasks regardless of the training paradigm and also on a related, but novel forelimb task, the Staircase. Horizontal ladder training led to full recovery of this task, and also limited recovery on the familiar but untrained single pellet grasping task. In comparison, single pellet grasping training led to a smaller improvement on the horizontal ladder, but interestingly the same degree of recovery on the single pellet grasping task as horizontal ladder trained animals. Both training groups performed equally well on a novel, untrained forelimb grasping task. These results show that task-specific forelimb training can lead to functional recovery also in non-trained, complex, forelimb movements. Anatomically, only single pellet grasping training was associated with enhanced sprouting of the intact corticospinal tract across the cervical spinal cord midline to innervate the denervated side of the spinal cord.