Sensorimotor impairments in rats with cerebral infarction, induced by unilateral occlusion of the left middle cerebral artery: strain differences and effects of the occlusion site

Validity and Reliability of Neurological Scores in Mice Exposed to Middle Cerebral Artery Occlusion

Background and Purpose- The selection of appropriate neurological scores and tests is crucial for the evaluation of stroke consequences. The validity and reliability of neurological deficit scores and tests has repeatedly been questioned in ischemic stroke models in the past. Methods- In 198 male mice exposed to transient intraluminal middle cerebral artery occlusion, we examined the validity and reliability of 11 neurological scores (Bederson score 0-3, Bederson score 0-4, Bederson score 0-5, modified neurological severity [0-14], subjective overall impression [0-10], or simple neurological tests: grip test, latency to move body length test, pole test, wire hanging test, negative geotaxis test, and elevated body swing test) in the acute stroke phase, that is, after 24 hours. Combinations of neurological scores or tests for predicting infarct volume were statistically analyzed. Results- Infarct volume was left skewed (median [Q1-Q3], 78.4 [54.8-101.3] mm³). Among all tests, the Bederson (0-5; r=0.63, P<0.001), modified neurological severity (r=0.80, P<0.001), and subjective overall impression (r=-0.63, P<0.001) scores had the highest test validities, using infarct volume as external reference. Subjective overall impression had the best agreement between 5 raters (Kendall W=0.11, P<0.001). The Bederson (0-5) score discriminated infarct volume in mice with small (≤50 mm³; r=0.33, P=0.027) and large (>50 mm³; r=0.48, P<0.001) brain infarcts, all other tests only in mice with large infarcts. Combining subjective overall impression with Bederson (0-5) score explained 47.6% of the variance of infarct volume. Conclusions- Despite their simplicity, the Bederson (0-5) score, modified neurological severity score, and subjective overall impression have reasonable validity and reliability in the acute stroke phase. The Bederson (0-5) score equally distinguishes infarct volume in small and large infarcts. Visual Overview- An online visual overview is available for this article.

The Effects of Exercise on Cognitive Recovery after Acquired Brain Injury in Animal Models: A Systematic Review

The objective of the present paper is to review the current status of exercise as a tool to promote cognitive rehabilitation after acquired brain injury (ABI) in animal model-based research. Searches were conducted on the PubMed, Scopus, and psycINFO databases in February 2014. Search strings used were: exercise (and) animal model (or) rodent (or) rat (and) traumatic brain injury (or) cerebral ischemia (or) brain irradiation. Studies were selected if they were (1) in English, (2) used adult animals subjected to acquired brain injury, (3) used exercise as an intervention tool after inflicted injury, (4) used exercise paradigms demanding movement of all extremities, (5) had exercise intervention effects that could be distinguished from other potential intervention effects, and (6) contained at least one measure of cognitive and/or emotional function. Out of 2308 hits, 22 publications fulfilled the criteria. The studies were examined relative to cognitive effects associated with three themes: exercise type (forced or voluntary), timing of exercise (early or late), and dose-related factors (intensity, duration, etc.). The studies indicate that exercise in many cases can promote cognitive recovery after brain injury. However, the optimal parameters to ensure cognitive rehabilitation efficacy still elude us, due to considerable methodological variations between studies.

Elevated body swing test after focal cerebral ischemia in rodents: methodological considerations

Background

The elevated body swing test (EBST) is a behavioral test used to evaluate experimental stroke in rodents. The basic idea is that when the animal is suspended vertically by the tail, it will swing its head laterally to the left or right depending on lesion side. In a previous study from our lab using the EBST after middle cerebral artery occlusion (MCAo), rats swung contralateral to the infarct day 1 post-MCAo, but ipsilateral day 3 post-MCAo. This shift was unexpected and prompted us to perform the present study. First, the literature was systematically reviewed to elucidate whether a similar shift had been noticed before, and if consensus existed regarding swing direction. Secondly, an experiment was conducted to systematically investigate the suggested behavior. Eighty-three adult male and female Sprague–Dawley rats were subjected to MCAo or sham surgery and the EBST was performed up to 7 days after the lesion.

Results

Both experimentally and through systematic literature review, the present study shows that the direction of biased swing activity in the EBST for rodents after cerebral ischemia can differ and even shift over time in some situations. The EBST curve for females was significantly different from that of males after the same occlusion time (p = 0.023).

Conclusions

This study highlights the importance of adequate reporting of behavioral tests for lateralization and it is concluded that the EBST cannot be recommended as a test for motor asymmetry after MCAo in rats.

Very-late-antigen-4 (VLA-4)-mediated brain invasion by neutrophils leads to interactions with microglia, increased ischemic injury and impaired behavior in experimental stroke

Neuronal injury from ischemic stroke is aggravated by invading peripheral immune cells. Early infiltrates of neutrophil granulocytes and T-cells influence the outcome of stroke. So far, however, neither the timing nor the cellular dynamics of neutrophil entry, its consequences for the invaded brain area, or the relative importance of T-cells has been extensively studied in an intravital setting. Here, we have used intravital two-photon microscopy to document neutrophils and brain-resident microglia in mice after induction of experimental stroke. We demonstrated that neutrophils immediately rolled, firmly adhered, and transmigrated at sites of endothelial activation in stroke-affected brain areas. The ensuing neutrophil invasion was associated with local blood-brain barrier breakdown and infarct formation. Brain-resident microglia recognized both endothelial damage and neutrophil invasion. In a cooperative manner, they formed cytoplasmic processes to physically shield activated endothelia and trap infiltrating neutrophils. Interestingly, the systemic blockade of very-late-antigen-4 immediately and very effectively inhibited the endothelial interaction and brain entry of neutrophils. This treatment thereby strongly reduced the ischemic tissue injury and effectively protected the mice from stroke-associated behavioral impairment. Behavioral preservation was also equally well achieved with the antibody-mediated depletion of myeloid cells or specifically neutrophils. In contrast, T-cell depletion more effectively reduced the infarct volume without improving the behavioral performance. Thus, neutrophil invasion of the ischemic brain is rapid, massive, and a key mediator of functional impairment, while peripheral T-cells promote brain damage. Acutely depleting T-cells and inhibiting brain infiltration of neutrophils might, therefore, be a powerful early stroke treatment.

Variation in behavioral deficits and patterns of recovery after stroke among different rat strains

Pre-clinical models of stroke therapeutics depend upon the ability to detect differences in infarct volume as well as in the short- and long-term outcomes of treated animals. Little attention has been paid to interstrain differences in these outcomes and the importance of defining the most appropriate behavioral tests. In this study, we evaluate long-term outcome from stroke in three different rat strains. Lewis, Wistar, and Sprague Dawley (SD) rats were subjected to 2-h middle cerebral artery occlusion and survived for up to 49 days. Behavioral tests were performed weekly. There was continuous assessment of rotational/circling activity in the home cage by use of an automated software program. A separate group of animals was sacrificed at 24 h to determine infarct volume. Infarct volume was similar in all three strains. Mortality was significantly higher in SD rats (P < 0.001). Rotational/circling activity at 24 h was correlated with cortical infarct volume in Wistar and SD rats (ρ = 0.67, P = 0.04 and ρ = 0.72, P = 0.01, respectively). Wistar and SD rats displayed more rotational/circling activity following stroke than Lewis rats, but Lewis rats evidenced more impairment on complex motor tasks like the rotarod. Further, computer automated analysis of rotational activity was more sensitive than subjective assessment, with SD rats showing a preference for clockwise rotations to 49 days after stroke despite normalization of the neurological score after 21 days. There are significant interstrain differences in survival and in the patterns of neurological impairment and recovery after stroke. These differences must be taken into account in pre-clinical studies, but may also be capitalized upon to understand genetic contributions to injury. Finally, computerized assessment of behavior is more sensitive than subjective assessment for detecting behavioral changes.

The intraluminal thread model revisited: rat strain differences in local cerebral blood flow

There are major differences in the outcome of focal cerebral ischemia between rat strains. This study aimed to investigate whether inter-strain differences exist in the local cerebral blood flow, changes produced by intraluminal middle cerebral artery occlusion (MCAO). Fifty-four male Long-Evans, Sprague-Dawley or Wistar rats were subjected to 60 minutes of transient MCAO, carried out with a silicone-coated 4-0 nylon monofilament. Local cerebral blood flow was monitored on the parietal cortex with laser-Doppler flowmetry. The decrease in local cerebral blood flow during the first 20 minutes of occlusion was significantly greater in Long-Evans (74.6 +/- 8.9%) than in Sprague-Dawley (50.7 +/- 26.8%) and Wistar (49.0 +/- 21.9%) rats. Strain differences in local cerebral blood flow reduction were maintained, or increased, throughout the occlusion period. These results show that the intraluminal model of MCAO produces a more pronounced, persistent and stable local cerebral blood flow reduction, with less interanimal variability, in Long-Evans than in Sprague-Dawley or Wistar rats.

PACAP and a novel stable analog protect rat brain from ischemia: Insight into the mechanisms of action

Pituitary adenylate cyclase-activating polypeptide (PACAP) shows potent protective effects in numerous models of neurological insults. However, the use of PACAP as a clinically efficient drug is limited by its poor metabolic stability. By combining identification of enzymatic cleavage sites with targeted chemical modifications, a metabolically stable and potent PACAP38 analog was recently developed. The neuroprotective activity of this novel compound was for the first time evaluated and compared to the native peptide using a rat model of middle cerebral artery occlusion (MCAO). Our results show that as low as picomolar doses of PACAP38 and its analog strongly reduce infarct volume and improve neurological impairment induced by stroke. In particular, these peptides inhibit the expression of Bcl-2-associated death promoter, caspase 3, macrophage inflammatory protein-1α, inducible nitric oxide synthase 2, tumor necrosis factor-α mRNAs, and increase extracellular signal-regulated kinase 2, B-cell CLL/lymphoma 2 and interleukin 6 mRNA levels. These results indicate that the neuroprotective effect of PACAP after MCAO is not only due to its ability to inhibit apoptosis but also to modulate the inflammatory response. The present study highlights the potential therapeutic efficacy of very low concentrations of PACAP or its metabolically stable derivative for the treatment of stroke.

A substance P antagonist improves outcome when administered 4 h after onset of ischaemic stroke

Previous studies have suggested that substance P (SP) plays a critical role in the development of brain oedema and functional deficits following traumatic brain injury and that SP receptor antagonism may improve outcome. No studies have described such a role in ischemic stroke. The present study characterized the effects of the NK1 tachykinin receptor antagonist, n-acetyl-L-tryptophan (NAT), on blood-brain barrier (BBB) breakdown, oedema formation, infarct volume and functional outcome following reversible ischemic stroke in rats. Ischemia was induced using a reversible thread model of middle cerebral artery occlusion where occlusion was maintained for 2 h before reperfusion. Animals received either NAT or equal volume saline vehicle intravenously at 2 h post-reperfusion. Ischaemic stroke resulted in increased perivascular SP immunoreactivity at 24 h. Administration of NAT significantly reduced oedema formation and BBB permeability at 24 h post-ischemia and significantly improved functional outcome as assessed over 7 days. There was no effect on infarct volume. We conclude that inhibition of SP activity with a NK1 tachykinin receptor antagonist is effective in reducing cerebral oedema, BBB permeability and functional deficits following reversible ischemia and may therefore represent a novel therapeutic approach to the treatment of ischaemic stroke.

Functional testing in a mouse stroke model induced by occlusion of the distal middle cerebral artery

Reducing post-stroke disability is the major goal of stroke therapy. Consequently, functional testing is essential in experimental stroke studies to increase the predictive value of animal models. We used several sensory and motor tests to assess functional disability in a mouse model of permanent distal middle cerebral artery occlusion (pdMCAO) that induced mainly cortical infarcts. Gait dynamics were transiently disturbed after pdMCAO as measured by different analysis techniques. Stance and brake duration were shorter after pdMCAO. Consistent with sensory and motor deficits the latency to move was prolonged up to 14 days after pdMCAO and the performance in the corner test and handedness were affected on day 1 or 2 after pdMCAO. Heart rate was decreased and heart rate variability were increased after pdMCAO indicating sympathetic-parasympathetic imbalance. In summary, pdMCAO-induced cortical infarcts lead to clinically relevant sensory, motor and cardiac autonomic dysfunction in mice. The present study provides a basis to explore the potential of functional testing for neuroprotection and neuroregeneration after stroke.

Long-term neuroprotective effects of carbon dioxide on neonatal rat hypoxic-ischemic brain injury: an experimental study of skilled motor tasks

OBJECTIVE

This study was undertaken to investigate the long-term effect of hypercapnia on neonatal hypoxic-ischemic brain injury, we tested its effect in a neonatal rat hypoxia-ischemia model.

STUDY DESIGN

The rats were subjected to unilateral carotid artery ligation and exposure to 8% oxygen for 30 minutes. Six percent carbon dioxide was administered to the neonatal rats during unilateral hypoxia-ischemia, and the motor function and neurologic outcomes were determined 3 months later.

RESULTS

Significant motor functional improvement was observed in the hypercapnic animals, as judged by the Montoya staircase test. The unilateral brain injury was significantly ameliorated in the hypercapnic animals, and this amelioration was well correlated with the motor functional performance. Cerebral blood flow during hypoxia-ischemia, monitored by laser Doppler flowmetry, was better preserved in the hypercapnic animals.

CONCLUSION

Our results suggest that mild hypercapnia during hypoxia-ischemia may provide long-lasting motor functional as well as neurologic protection for immature brains, possibly by increasing cerebral blood flow during hypoxia.

Long-term effects of immunotoxic cholinergic lesions in the septum on acquisition of the cone-field task and noncognitive measures in rats

In rats, nonspecific mechanical or neurotoxic lesions of the septum impair spatial memory in, e.g., Morris water- and radial-maze tasks. Unfortunately, the lack of specificity of such lesions limits inferences about the role of the cholinergic hippocampal projections in spatial cognition. We therefore tested the effects of septal lesions produced by 192 IgG-saporin in rats, which is highly selective for basal forebrain cholinergic neurons, on home cage activity, noncognitive tests (modified Irwin test, open field and forced swimming tests, and various sensorimotor tasks), and the cone-field spatial learning task. The immunotoxic lesion reduced acetylcholine (ACh) levels in the septum (-61%) and hippocampus (>-75%). Rats with lesions showed mild home-cage hyperactivity at 4 weeks postlesion, but no noncognitive deficits at 13 weeks postsurgery. In the cone-field task, rats with septal lesions made more working- and reference-memory errors than the controls, but acquisition curves were parallel in both groups. The speed of visiting cones was faster in the rats with lesions, indicative of disturbed attention or increased motivation. These data support the growing evidence that involvement of the septohippocampal cholinergic system in spatial learning and memory may have been overestimated in studies that used lesions with poor selectivity.

Brain injury and neurofunctional deficit in neonatal mice with hypoxic-ischemic encephalopathy

Birth asphyxia accounts for the majority of developmental motor and cognitive deficits. Studies were undertaken to develop a reproducible murine model of perinatal hypoxic-ischemic encephalopathy (HIE) which would permit both anatomic and neurofunctional quantification of injury. Short-term neurofunctional outcomes consisted of three developmental reflexes (righting, cliff aversion and geotaxis) assessed in 7-day-old mouse pups 24 h after unilateral carotid artery ligation followed by inhalation of 8% oxygen. Cerebral infarct volume was dependent on duration of hypoxia, being approximately 2.5-fold greater with longer (60 min) versus shorter (30 min) hypoxia exposure (P=0.001). All three sensorimotor neonatal reflexes assessed at 24 h after HIE injury correlated significantly with long-term neurofunction evaluated using a water-maze test of navigational learning and memory assessed 8 weeks later in the same animals. Cerebral atrophy, a delayed consequence of HIE in this model, also correlated strongly with water-maze performance (r=0.86, P=0.002). These data demonstrate for the first time that murine neonatal sensorimotor reflex performance can be rigorously quantified in the acute phase of perinatal HIE and has strong predictive value not only for anatomic extent of cerebral injury, but also for long-term neurofunctional outcome.

Long-term neuroprotective effects of hypothermia on neonatal hypoxic-ischemic brain injury in rats, assessed by auditory brainstem response

A method to assess long-term neurofunctional outcome of hypothermia on immature brains has not yet been clearly established. To investigate the effects of hypothermia on long-term neurofunctional outcome, we studied brainstem function using auditory brainstem response in adult rats after neonatal hypoxic-ischemic brain injury. Seven-day-old rats underwent a combination of left common carotid artery ligation and subsequent exposure to 8% O(2) for 1 h (n = 17). The rats were divided into three groups: hypothermia group (n = 6), normothermia group (n = 6), and sham control group (n = 5). During recovery from the hypoxic-ischemic insult, body temperature was reduced to 30 degrees C for 24 h in the hypothermia group, but was kept at 37 degrees C in the normothermia and sham control group. Three months later the rats were assessed by auditory brainstem response, then killed. The normothermia group showed increased III-V latencies and wave V abnormalities. Hypothermia significantly ameliorated wave V abnormalities. Injury to the ipsilateral inferior colliculus was also reduced in the hypothermia group compared with that in the normothermia group, and the degree of damage assessed histologically correlated well with auditory brainstem response findings. The current study demonstrates that postischemic hypothermia may provide effective and long-lasting neurofunctional as well as histopathologic protection to the immature brain.

Mild focal cerebral ischemia in the rat. The effect of local temperature on infarct size

We aimed at investigating a new model of mild focal cerebral ischemia in rats with repeated, noninvasive magnetic resonance scanning combined with histology. Magnetic resonance imaging yielded information about infarct development enabling us to test the putative growth of the infarct over time. The effect of local temperature at the occlusion site in this model was furthermore tested. Thirty-three Wistar rats were subjected to 30 min of simultaneous common carotid artery and distal middle cerebral artery occlusion or sham treatment. Animals were magnetic resonance-scanned repeatedly between day one and day 14 after surgery, then sacrificed, and paraffin brain sections stained. All animals scanned 24 h after reperfusion showed an area of edema in the affected cortex, which later was identified as an infarct. Animals with a temperature of 33.9 +/- 1.5 degrees C at the MCA site (hypothermic) showed smaller infarcts (14.4 +/- 10 mm3) than animals with normothermic local temperature (36.7 +/- 0.2 degrees C, 57.7 +/- 26.4 mm3). Infarct size was maximal on day 3 after ischemia but decreased as edema subsided. Infarct volumes from histology and magnetic resonance imaging correlated well. The model reproducibly yielded cortical infarcts, which did not grow after edema had subsided. Local temperature had a considerable effect on final infarct size.

The hippocampus in spontaneously hypertensive rats: an animal model of vascular dementia?

Hypertension is a main risk factor for cerebrovascular disease, including vascular dementia. The present study was designed to evaluate if hypertension-dependent changes of the hippocampus of spontaneously hypertensive rats (SHR) of different ages were related with those occurring in vascular dementia. The hippocampus was chosen as the brain area involved in learning and memory. Systolic pressure was slightly increased in 2-month-old SHR in comparison with age-matched normotensive Wistar-Kyoto (WKY) rats and augmented progressively with age in SHR. No microanatomical changes were observed in the hippocampus of SHR of 2 months in comparison with age-matched WKY rats. A limited decrease of white matter volume was observed in 4-month-old SHR. In SHR of 6 months, a reduction of grey matter volume both in the CA1 subfield and in the dentate gyrus occurred. Evaluation of phosphorylated 200-kDa neurofilament immunoreactivity revealed a decreased immune reaction area in the CA1 subfield of 6-month-old SHR compared to age-matched WKY rats and no changes in the expression and localization of the dendritic marker microtubule associated protein (MAP)-2. In 6-month-old SHR, an increase of glial fibrillary acidic protein (GFAP)-expression was found by Western blot analysis. Immunohistochemistry revealed an increase in number (hyperplasia), but not in size of astrocytes. These findings indicate the occurrence of cytoskeletal breakdown and astroglial changes primarily in the CA1 subfield of the hippocampus of SHR of 6 months. The occurrence in the hippocampus of SHR of regressive changes and astroglial reaction similar to those occurring in neurodegenerative disorders with cognitive impairment suggests that they represent an animal model of vascular dementia.

Effects of neonatal hypoxic-ischemic brain injury on skilled motor tasks and brainstem function in adult rats

In an attempt to establish more sensitive long-term neurofunctional measurements for neonatal hypoxic-ischemic brain injury, we examined skilled motor task and brainstem functions in adult rats after neonatal cerebral hypoxia-ischemia (H-I), using a staircase test and auditory brainstem response (ABR), respectively. Seven-day-old rats underwent a combination of left common carotid artery ligation and exposure to 8% O(2) for 1 h (n=16). The control animals only received sham operation (n=16). At 3 months of age, the staircase test and ABR were performed. In the staircase test, H-I animals showed marked impairment of skilled forelimb use in the side contralateral to the occluded artery, and the degree of brain damage correlated significantly to skilled forelimb use. In the ABR, H-I animals showed brainstem dysfunction assessed by measuring interpeak latencies for waves III-V and I-V. We also examined the brainstem with antibodies specific for activated caspase-3, a protein involved in initiation of apoptosis, and observed that caspase-3 was activated in the ipsilateral inferior colliculus at 24 h after H-I. The present study shows that both the staircase test and ABR are sensitive and objective long-term neurofunctional measurements that can be used in future studies to assess therapeutic intervention in this neonatal cerebral H-I model.

BTS 72664-- a novel CNS drug with potential anticonvulsant, neuroprotective, and antimigraine properties

BTS 72664, (R)-7-[1-(4-chlorophenoxy)]ethyl]-1,2,4-triazolo(1,5-alpha)pyrimidine, was identified as a drug development candidate from a research program designed to discover novel, broad-spectrum, non-sedative anticonvulsant drugs. BTS 72664 antagonized bicuculline (BIC)- and maximal electroshock (MES)-induced convulsions with ED(50) values of 1.9 and 47.5 mg/kg p.o., respectively. In rodents, it has a wide spectrum of activity preventing seizures induced by picrotoxin, pentylenetetrazol, i.c.v. 4-aminopyridine or NMDA, and audiogenic seizures in DBA-2 mice and GEPR-9 rats. BTS 72664 was also effective in preventing convulsions in amygdala-kindled rats The lack of sedative potential was predicted on the basis of wide separation between ED(50) in anticonvulsant models and TD(50) for motor impairment in mice in rotating rod and inverted horizontal grid tests. BTS 72664 is likely to produce its anticonvulsant effect by enhancing chloride currents through picrotoxin-sensitive chloride channels, and by weak inhibition of Na(+) and NMDA channels. It does not act, however, at the benzodiazepine binding site. In addition to its potential use in the treatment of epilepsy BTS 72664 may be useful in the treatment of stroke. At 50 mg/kg p.o. x 4, given to rats at 12 hourly intervals, starting at 15 min after permanent occlusion of middle cerebral artery (MCA), it reduced cerebral infarct size by 31% (measured at 2 days after insult) and accelerated recovery in a functional behavioral model. BTS 72664 prevented increases in extraneuronal concentrations of glutamate, glycine and serine brain levels induced by a cortical insult to rats (cf. cortical spreading depression). It may, therefore, have also antimigraine activity.

Cognitive and behavioral assessment in experimental stroke research: will it prove useful?

Stroke in humans is associated with deficits in sensorimotor and cognitive function. Consequently, many stroke researchers recently have expanded their techniques to assess cognitive and behavioral correlates of histologically-determined stroke damage in animal models. Although the incorporation of functional outcome assessment represents an important step forward in stroke research, reports of middle cerebral artery occlusion (MCAO) induced behavioral deficits often conflict, and a significant correlation between post-stroke histology and behavior has been reported in few stroke studies. Discrepancies in behavioral outcomes among studies may be due to several factors, such as method of MCAO, duration of occlusion, strain, the timing and method of the behavioral testing and the laboratory environment. Furthermore, proper experimental and control groups, necessary to rule out potential confounding factors during cognitive testing, often are not incorporated. The goal of this review is: (1) to provide a description of the techniques most commonly employed to assess functional outcome after (MCAO) in rodents and (2) to identify potential confounding factors that may interfere with a clear interpretation of the behavioral data.

Upregulation of ICAM-1 and MCP-1 but not of MIP-2 and sensorimotor deficit in response to traumatic axonal injury in rats

The pathophysiology of traumatic axonal injury (TAI) is only partially understood. In this study, we investigated the inflammatory response as well as the extent of neurological deficit in a rat model of traumatic brain injury (TBI). Forty-two adult rats were subjected to moderate impact-acceleration brain injury and their brains were analyzed immunohistochemically for ICAM-1 expression and neutrophil infiltration from 1 hr up to 14 days after trauma. In addition, the chemotactic factors MIP-2 and MCP-1 were measured in brain homogenates by ELISA. For evaluating the neurological deficit, three sensorimotor tests were applied for the first time in this model. In the first 24 hr after trauma, the number of ICAM-1 positive vessels increased up to 4-fold in cortical and subcortical regions compared with sham operated controls (P < 0.05). Maximal ICAM-1 expression (up to 8-fold increase) was detected after 4 days (P < 0.001 vs. 24 hr), returning to control levels in all brain regions by 7 days after trauma. MCP-1 was elevated between 4 hr and 16 hr post-injury as compared with controls. In contrast, neither neutrophil infiltration nor elevation of MIP-2, both events relevant in focal brain injury, could be detected. In all neurological tests, a significant deficit was observed in traumatized rats as compared with sham operated animals from Day 1 post-injury (grasping reflex of the hindpaws: P < 0.001, vibrissae-evoked forelimb placing: P = 0.002, lateral stepping: P = 0.037). In conclusion, after moderate impact acceleration brain injury ICAM-1 upregulation has been demonstrated in the absence of neutrophil infiltration and is paralleled by a selective induction of chemokines, pointing out that individual and distinct inflammatory events occur after diffuse vs. focal TBI.

Cognitive deficits after focal cerebral ischemia in mice

BACKGROUND AND PURPOSE

The interpretation of cognitive data in many experimental stroke studies is problematic because middle cerebral artery occlusion (MCAO) is associated with sensorimotor alterations that may become confounding factors in cognitive testing. The purpose of the current study was to determine if it is possible to measure MCAO-induced cognitive deficits by using short durations of ischemia that do not result in alterations in sensorimotor behavior in mice.

METHODS

Male C57/Bl6 mice were subjected to 60 or 90 minutes of intraluminal MCAO or sham surgery. In the first cohort of animals (n=12/group), locomotor activity, balance, and coordination were evaluated 2 weeks after surgery. In a second cohort of animals (n=10/group), the effects of 60 minutes of MCAO on subsequent learning and memory were assessed with a step-down passive avoidance task beginning 1 week after surgery. In a third cohort of animals (n=8 to 10/group), training in a passive avoidance task was completed before 60 minutes of MCAO, then retention of the task was assessed 1 week after surgery. In all animals, infarction size was determined after 14 days of reperfusion with use of cresyl violet staining and quantitative image analysis.

RESULTS

There was no significant difference in infarction volume in the cerebral cortex or caudoputamen after 60 versus 90 minutes of MCAO. However, there was a significant increase in latency to move 1 body length in the 90-minute MCAO group compared with the 60-minute MCAO and sham groups. In 2 additional cohorts of animals, 60-minute MCAO was associated with a deficit in the acquisition and retention of a passive avoidance task regardless of whether the task training occurred before or after MCAO.

CONCLUSIONS

Long-term cognitive deficits can be induced in mice by using a short duration of MCAO (60 minutes) that does not result in concomitant sensorimotor deficits.

sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl)-piperidine affords neuroprotection from focal ischemia with prolonged reperfusion

BACKGROUND AND PURPOSE

We previously showed that the intravenous administration of the potent final sigma(1)-receptor ligand 4-phenyl-1-(4-phenylbutyl)-piperidine (PPBP) provides neuroprotection against transient focal cerebral ischemia and that the protection depends on treatment duration. We tested the hypothesis that PPBP would provide neuroprotection in a model of transient focal ischemia and 7 days of reperfusion in the rat as assessed with neurobehavioral outcome and infarction volume.

METHODS

Under the controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 hours of middle cerebral artery occlusion (MCAO) with the intraluminal suture occlusion technique. We used laser Doppler flowmetry to assess MCAO. At 60 minutes after the onset of ischemia, rats were randomly assigned to 1 of 4 treatment groups in a blinded fashion and received a continuous intravenous infusion of control saline or 0.1, 1, or 10 micromol. kg(-1). h(-1) PPBP for 24 hours. Neurobehavioral evaluation was performed at baseline (3 to 4 days before MCAO) and at 3 and 7 days of reperfusion. Infarction volume was assessed with triphenyltetrazolium chloride staining on day 7 of reperfusion in all rats.

RESULTS

Triphenyltetrazolium chloride-determined infarction volume of ipsilateral cortex was smaller in rats treated with 10 micromol. kg(-1). h(-1) PPBP (n=15, 68+/-12 mm(3), 18+/-3% of contralateral structure, P<0.05) (mean+/-SEM) compared with corresponding rats treated with saline (n=15, 114+/-11 mm(3), 31+/-3% of contralateral structure). PPBP did not provide significant neuroprotection in the caudoputamen complex. Although MCAO was associated with several alterations in behavior, the treatment with PPBP had no effect on behavioral outcomes.

CONCLUSIONS

The data demonstrate that the potent final sigma(1)-receptor ligand PPBP decreases cortical infarction volume without altering neurobehavior after transient focal ischemia and prolonged reperfusion in the rat.

Effects of subdural haematoma on sensorimotor functioning and spatial learning in rats

Twenty per cent of all strokes are haemorrhagic in character and are associated with severe disturbances in sensorimotor behaviour and cognition. Although spontaneous recovery of pre-stroke functioning occurs in some cases, the process is demanding, slow, and often incomplete. A first step in the preclinical testing of new putative, neuroprotective and recovery-supporting therapeutics is to validate animal models of brain injury. In a series of four experiments we evaluated the behavioural impairments and the time course of recovery of functional deficits in rats with an experimentally induced subdural haematoma. We found that unilateral subdural haematoma resulted in dysfunction in both simple reflexive (experiment 1) and skilled sensorimotor behaviour (experiment 2). Reflexive behaviour did not recover, or recovered only marginally, and neither did the deficits in skilled forepaw use. Bilateral subdural haematoma impaired the learning and memory performance of adult (experiment 3) and old rats (experiment 4) in the Morris water escape task. Considering the diversity of the deficits found in our experiments, we conclude that different models are needed to cover the broad range of deficits seen in stroke patients.