Definition of the anterior choroidal artery territory in rats using intraluminal occluding technique

The Head and Neck Vascular Anatomical Variability in the Laboratory Rat and its Significance to Medical Science

Laboratory rats are often used in experimental research of concern to human and veterinary medicine. There are several advantages of using rats as a scientific medium. In this study rats will be used as the scientific model as, previously discussed, they have proven their effectiveness in cardiovascular studies. The aim is to give a description of the cranial region, the head and neck of the rat as well as imaging of the vasculature of these regions to support the planning of surgical therapeutic methods to be applied to human and veterinary medical research. The research of the blood vessels morphology in anatomical studies is key to the prevention of ischemia during organ surgery. In recent times the laboratory rat has become one of the most popular models for experiments in medical research. Corrosion casts were prepared on the cranial arteries of the body of 20 adult Wistar rats using Duracryl Dental® and PUR SP as the casting medium. We found the absence of the brachiocephalic trunk in some cases. Thyroid arteries originated independently or by the short common trunk from the right and left common carotid artery. The facial artery originated by the short trunk with the maxillary artery, or by the linguofacial trunk with the lingual artery from the common carotid artery. The results of this study revealed that, the functional anatomical relationship between the rat neck and head structures are important for the development of medical research of concern to human and veterinary experimental medicine.

A System for Continuous Pre- to Post-reperfusion Intra-carotid Cold Infusion for Selective Brain Hypothermia in Rodent StrokeModels

Intra-carotid cold infusion (ICCI) appears as a promising method for hypothermia-mediated brain protection from ischemic stroke. Recent clinical pilot studies indicate easy implementation of ICCI into endovascular acute ischemic stroke treatment. Current rodent ICCI-in-stroke models limit ICCI to the post-reperfusion phase. To establish a method for continuous ICCI over the duration of intra-ischemia to post-reperfusion in rodent stroke models, a novel system was developed. Eighteen male Sprague-Dawley rats were included. Intraluminal filament method was used for transient middle cerebral artery occlusion (MCAO). Normal saline (~ 0 °C) was delivered (≤ 2.0 mL/min) into the internal carotid artery via a customized infusion system without interruption during MCAO (intra-ischemia) to after filament withdrawal (post-reperfusion). Bilateral cortical and striatal temperatures were monitored. Hypothermia goals were a temperature reduction in the ischemic hemisphere by 2 °C prior to reperfusion and thereafter maintenance of regional brain hypothermia at ~ 32 °C limiting the administered ICCI volume to ½ of each rat's total blood volume. During ischemia, maximum brain cooling rate was achieved with ICCI at 0.5 mL/min. It took 2 min to reduce ischemic striatal temperature by 2.3 ± 0.3 °C. After reperfusion, brain cooling was continued at 2 mL/min ICCI first (over 42 s) and maintained at 32.1 ± 0.3 °C at 0.7 mL/min ICCI over a duration of 15 ± 0.8 min. ICCI (total 12.6 ± 0.6 mL) was uninterrupted over the duration of the studied phases. First system that allows continuous ICCI during the phases of intra-ischemia to post-reperfusion in small animals for selective brain cooling and for investigations of other neuroprotective infusions.

A Working Module for the Neurovascular Unit in the Sexually Dimorphic Nucleus of the Preoptic Area

The neurovascular unit (NVU) can be conceptualized as a functional entity consisting of neurons, astrocytes, pericytes, and endothelial and smooth muscle cells that operate in concert to affect blood flow to a very circumscribed area. Although we are currently in a "golden era" of bioengineering, there are, as yet, no living NVUs-on-a-chip modules available and the development of a neural chip that would mimic NVUs is a seemingly lofty goal. The sexually dimorphic nucleus of the preoptic area (SDN-POA) is a tiny brain structure (between 0.001~0.007 mm³ in rats) with an assessable biological function (i.e., male sexual behavior). The present effort was undertaken to determine whether there are identifiable NVUs in the SDN-POA by assessing its vasculature relative to its known neural components. First, a thorough and systematic review of thousands of histologic and immunofluorescent images from 201 weanling and adult rats was undertaken to define the characteristics of the vessels supplying the SDN-POA: its primary supply artery/arteriole and capillaries are physically inseparable from their neural elements. A subsequent immunofluorescent study targeting α-smooth muscle actin confirmed the identity of an artery/arteriole supplying the SDN-POA. In reality, the predominant components of the SDN-POA are calbindin D28k-positive neurons that are comingled with tyrosine hydroxylase-positive projections. Finally, a schematic of an SDN-POA NVU is proposed as a working model of the basic building block of the CNS. Such modules could serve the study of neurovascular mechanisms and potentially inform the development of next generation bioengineered neural transplants, i.e., the construct of an NVU neural chip.

An Experimental Infarct Targeting the Internal Capsule: Histopathological and Ultrastructural Changes

BACKGROUND

Stroke involving the cerebral white matter (WM) has increased in prevalence, but most experimental studies have focused on ischemic injury of the gray matter. This study was performed to investigate the WM in a unique rat model of photothrombotic infarct targeting the posterior limb of internal capsule (PLIC), focusing on the identification of the most vulnerable structure in WM by ischemic injury, subsequent glial reaction to the injury, and the fundamental histopathologic feature causing different neurologic outcomes.

METHODS

Light microscopy with immunohistochemical stains and electron microscopic examinations of the lesion were performed between 3 hours and 21 days post-ischemic injury.

RESULTS

Initial pathological change develops in myelinated axon, concomitantly with reactive change of astrocytes. The first pathology to present is nodular loosening to separate the myelin sheath with axonal wrinkling. Subsequent pathologies include rupture of the myelin sheath with extrusion of axonal organelles, progressive necrosis, oligodendrocyte degeneration and death, and reactive gliosis. Increase of glial fibrillary acidic protein (GFAP) immunoreactivity is an early event in the ischemic lesion. WM pathologies result in motor dysfunction. Motor function recovery after the infarct was correlated to the extent of PLIC injury proper rather than the infarct volume.

CONCLUSIONS

Pathologic changes indicate that the cerebral WM, independent of cortical neurons, is highly vulnerable to the effects of focal ischemia, among which myelin sheath is first damaged. Early increase of GFAP immunoreactivity indicates that astrocyte response initially begins with myelinated axonal injury, and supports the biologic role related to WM injury or plasticity. The reaction of astrocytes in the experimental model might be important for the study of pathogenesis and treatment of the WM stroke.

The choroid plexus as a site of damage in hemorrhagic and ischemic stroke and its role in responding to injury

While the impact of hemorrhagic and ischemic strokes on the blood–brain barrier has been extensively studied, the impact of these types of stroke on the choroid plexus, site of the blood-CSF barrier, has received much less attention. The purpose of this review is to examine evidence of choroid plexus injury in clinical and preclinical studies of intraventricular hemorrhage, subarachnoid hemorrhage, intracerebral hemorrhage and ischemic stroke. It then discusses evidence that the choroid plexuses are important in the response to brain injury, with potential roles in limiting damage. The overall aim of the review is to highlight deficiencies in our knowledge on the impact of hemorrhagic and ischemic strokes on the choroid plexus, particularly with reference to intraventricular hemorrhage, and to suggest that a greater understanding of the response of the choroid plexus to stroke may open new avenues for brain protection.

Stroke Lesions in a Large Upper Limb Rehabilitation Trial Cohort Rarely Match Lesions in Common Preclinical Models

BACKGROUND

Stroke patients with mild-moderate upper extremity motor impairments and minimal sensory and cognitive deficits provide a useful model to study recovery and improve rehabilitation. Laboratory-based investigators use lesioning techniques for similar goals.

OBJECTIVE

To determine whether stroke lesions in an upper extremity rehabilitation trial cohort match lesions from the preclinical stroke recovery models used to drive translational research.

METHODS

Clinical neuroimages from 297 participants enrolled in the Interdisciplinary Comprehensive Arm Rehabilitation Evaluation (ICARE) study were reviewed. Images were characterized based on lesion type (ischemic or hemorrhagic), volume, vascular territory, depth (cortical gray matter, cortical white matter, subcortical), old strokes, and leukoaraiosis. Lesions were compared with those of preclinical stroke models commonly used to study upper limb recovery.

RESULTS

Among the ischemic stroke participants, median infarct volume was 1.8 mL, with most lesions confined to subcortical structures (61%) including the anterior choroidal artery territory (30%) and the pons (23%). Of ICARE participants, <1% had lesions resembling proximal middle cerebral artery or surface vessel occlusion models. Preclinical models of subcortical white matter injury best resembled the ICARE population (33%). Intracranial hemorrhage participants had small (median 12.5 mL) lesions that best matched the capsular hematoma preclinical model.

CONCLUSIONS

ICARE subjects are not representative of all stroke patients, but they represent a clinically and scientifically important subgroup. Compared with lesions in general stroke populations and widely studied animal models of recovery, ICARE participants had smaller, more subcortically based strokes. Improved preclinical-clinical translational efforts may require better alignment of lesions between preclinical and human stroke recovery models.

Circumscribed Capsular Infarct Modeling Using a Photothrombotic Technique

Recent increase in the prevalence rate of white matter stroke demands specific research in the field. However, the lack of a pertinent animal model for white matter stroke has hampered research investigations. Here, we describe a novel method for creating a circumscribed capsular infarct that minimizes damage to neighboring gray matter structures. We used pre-surgery neural tracing with adeno-associated virus-green fluorescent protein (AAV-GFP) to identify somatotopic organization of the forelimb area within the internal capsule. The adjustment of light intensity based on different optical properties of gray and white matter contributes to selective destruction of white matter with relative preservation of gray matter. Accurate positioning of optical-neural interface enables destruction of entire forelimb area in the internal capsule, which leads to a marked and persistent motor deficit. Thus, this technique produces highly replicable capsular infarct lesions with a persistent motor deficit. The model will be helpful not only to study white matter stroke (WMS) at the behavioral, circuit, and cellular levels, but also to assess its usefulness for development of new therapeutic and rehabilitative interventions.

Ischemic penumbra as a trigger for intracranial pressure rise - A potential cause for collateral failure and infarct progression?

We have recently shown that intracranial pressure (ICP) increases dramatically 24 h after minor intraluminal thread occlusion with reperfusion, independent of edema. Some of the largest ICP rises were observed in rats with the smallest final infarcts. A possible alternate mechanism for this ICP rise is an increase of cerebrospinal fluid (CSF) volume secondary to choroid plexus damage (a known complication of the intraluminal stroke model used). Alternatively, submaximal injury may be needed to induce ICP elevation. Therefore, we aimed to determine (a) if choroid plexus damage contributes to the ICP elevation, (b) if varying the patency of an important internal collateral supply to the middle cerebral artery (MCA), the anterior choroidal artery (AChA), produces different volumes of ischemic penumbra and (c) if presence of ischemic penumbra (submaximal injury) is associated with ICP elevation. We found (a) no association between choroid plexus damage and ICP elevation, (b) animals with a good internal collateral supply through the AChA during MCAo had significantly larger penumbra volumes and (c) ICP elevation at ≈24 h post-stroke only occurred in rats with submaximal injury, shown in two different stroke models. We conclude that active cellular processes within the ischemic penumbra may be required for edema-independent ICP elevation.

Hypothalamic, thalamic and hippocampal lesions in the mouse MCAO model: Potential involvement of deep cerebral arteries?

Intraluminal monofilament occlusion of the middle cerebral artery (MCAO) in mice is the most used rodent model to study the pathophysiology of stroke. However, this model often shows brain damage in regions not supplied by the MCA such as the hypothalamus, hippocampus and thalamus. Several studies have suggested some explanations on these localized infarcts. We aim to provide an alternative explanation which could allow each experimenter to better grasp the MCAO model. We propose that the MCA occlusion by the monofilament also occludes deep and small cerebral arteries arising directly from the internal carotid artery, proximally to the origin of MCA. Then, drawbacks and pitfalls of the MCAO model must be appreciated and the almost systematic risk of inducing lesions in some unwanted territories for neuroanatomical reasons, i.e. vascular connections between deep arteries and hypothalamic, thalamic and hippocampal areas in rodents has to be integrated.

Lasting pure-motor deficits after focal posterior internal capsule white-matter infarcts in rats

Small white-matter infarcts of the internal capsule are clinically prevalent but underrepresented among currently available animal models of ischemic stroke. In particular, the assessment of long-term outcome, a primary end point in clinical practice, has been challenging due to mild deficits and the rapid and often complete recovery in most experimental models. We, therefore, sought to develop a focal white-matter infarction model that can mimic the lasting neurologic deficits commonly observed in stroke patients. The potent vasoconstrictor endothelin-1 (n=24) or vehicle (n=9) was stereotactically injected into the internal capsule at one of three antero-posterior levels (1, 2, or 3 mm posterior to bregma) in male Sprague-Dawley rats. Endothelin-injected animals showed highly focal (~1 mm(3)) and reproducible ischemic infarcts, with severe axonal and myelin loss accompanied by cellular infiltration when examined 2 and 4 weeks after injection. Only those rats injected with endothelin-1 at the most posterior location developed robust and pure-motor deficits in adhesive removal, cylinder and foot-fault tests that persisted at 1 month, without detectable sensory impairments. In summary, we present an internal capsule stroke model optimized to produce lasting pure-motor deficits in rats that may be suitable to study neurologic recovery and rehabilitation after white-matter injury.

A novel mouse model of subcortical infarcts with dementia

Subcortical white matter (WM) is a frequent target of ischemic injury and extensive WM lesions are important substrates of vascular cognitive impairment (VCI) in humans. However, ischemic stroke rodent models have been shown to mainly induce cerebral infarcts in the gray matter, while cerebral hypoperfusion models show only WM rarefaction without infarcts. The lack of animal models consistently replicating WM infarct damage may partially explain why many neuroprotective drugs for ischemic stroke or VCI have failed clinically, despite earlier success in preclinical experiments. Here, we report a novel animal model of WM infarct damage with cognitive impairment can be generated by surgical implantation of different devices to the right and left common carotid artery (CCA) in C57BL/6J mice. Implantation of an ameroid constrictor to the right CCA resulted in gradual occlusion of the vessel over 28 d, whereas placement of a microcoil to the left CCA induced ∼50% arterial stenosis. Arterial spin labeling showed a gradual reduction of cerebral blood flow over 28 d post operation. Such reductions were more marked in the right, compared with the left, hemisphere and in subcortical, rather than the cortical, areas. Histopathological analysis showed multiple infarct damage in right subcortical regions, including the corpus callosum, internal capsule, hippocampal fimbria, and caudoputamen, in 81% of mice. Mice displaying such damage performed significantly poorer in locomotor and cognitive tests. The current mouse model replicates the phenotypes of human subcortical VCI, including multiple WM infarcts with motor and cognitive impairment.

A rat model of photothrombotic capsular infarct with a marked motor deficit: a behavioral, histologic, and microPET study

We present a new method for inducing a circumscribed subcortical capsular infarct (SCI), which imposes a persistent motor impairment in rats. Photothrombotic destruction of the internal capsule (IC) was conducted in Sprague Dawley rats (male; n=38). The motor performance of all animals was assessed using forelimb placing, forelimb use asymmetry, and the single pellet reaching test. On the basis of the degree of motor recovery, rats were subdivided into either the poor recovery group (PRG) or the moderate recovery group (MRG). Imaging assessment of the impact of SCI on brain metabolism was performed using 2-deoxy-2-[(18)F]-fluoro-D-glucose ([(18)F]-FDG) microPET (positron emission tomography). Photothrombotic lesioning using low light energy selectively disrupted circumscribed capsular fibers. The MRG showed recovery of motor performance after 1 week, but the PRG showed a persistent motor impairment for >3 weeks. Damage to the posterior limb of the IC (PLIC) is more effective for producing a severe motor deficit. Analysis of PET data revealed decreased regional glucose metabolism in the ipsilesional motor and bilateral sensory cortex and increased metabolism in the contralesional motor cortex and bilateral hippocampus during the early recovery period after SCI. Behavioral, histologic, and functional imaging findings support the usefulness of this novel SCI rat model for investigating motor recovery.

Inadvertent occlusion of the anterior choroidal artery explains infarct variability in the middle cerebral artery thread occlusion stroke model

Intraluminal occlusion of the middle cerebral artery (MCAo) in rodents is perhaps the most widely used model of stroke, however variability of infarct volume and the ramifications of this on sample sizes remains a problem, particularly for preclinical testing of potential therapeutics. Our data and that of others, has shown a dichotomous distribution of infarct volumes for which there had previously been no clear explanation. When studying perfusion computed tomography cerebral blood volume (CBV) maps obtained during intraluminal MCAo in rats, we observed inadvertent occlusion of the anterior choroidal artery (AChAo) in a subset of animals. We hypothesized that the combined occlusion of the MCA and AChA may be a predictor of larger infarct volume following stroke. Thus, we aimed to determine the correlation between AChAo and final infarct volume in rats with either temporary or permanent MCA occlusion (1 h, 2 h, or permanent MCAo). Outbred Wistar rats (n = 28) were imaged prior to and immediately following temporary or permanent middle cerebral artery occlusion. Presence of AChAo on CBV maps was shown to be a strong independent predictor of 24 h infarct volume (β = 0.732, p <0.001). This provides an explanation for the previously observed dichotomous distribution of infarct volumes. Interestingly, cortical infarct volumes were also larger in rats with AChAo, although the artery does not supply cortex. This suggests an important role for perfusion of the MCA territory beyond the proximal occlusion through AChA-MCA anastomotic collateral vessels in animals with a patent AChAo. Identification of combined MCAo and AChAo will allow other investigators to tailor their stroke model to reduce variability in infarct volumes, improve statistical power and reduce sample sizes in preclinical stroke research.

Low oral doses of bisphenol A increase volume of the sexually dimorphic nucleus of the preoptic area in male, but not female, rats at postnatal day 21

Perinatal treatment with relatively high doses of bisphenol A (BPA) appears to have little effect on volume of the rodent sexually dimorphic nucleus of the preoptic area (SDN-POA). However, doses more relevant to human exposures have not been examined. Here, effects of pre- and post-natal treatment with low BPA doses on SDN-POA volume of postnatal day (PND) 21 Sprague-Dawley rats were evaluated. Pregnant rats were orally gavaged with vehicle, 2.5 or 25.0 μg/kg BPA, or 5.0 or 10.0 μg/kg ethinyl estradiol (EE₂) on gestational days 6-21. Beginning on the day after birth, offspring were orally treated with the same dose their dam had received. On PND 21, offspring (n=10-15/sex/group; 1/sex/litter) were perfused and volume evaluation was conducted blind to treatment. SDN-POA outline was delineated using calbindin D28K immunoreactivity. Pairwise comparisons of the significant treatment by sex interaction indicated that neither BPA dose affected female volume. However, females treated with 5.0 or 10.0 μg/kg EE₂ exhibited volumes that were larger than same-sex controls, respectively (p<0.001). Males treated with either BPA dose or 10.0 μg/kg/day EE₂ had larger volumes than same-sex controls (p<0.006). These data indicate that BPA can have sex-specific effects on SDN-POA volume and that these effects manifest as larger volumes in males. Sensitivity of the methodology as well as the treatment paradigm was confirmed by the expected EE₂-induced increase in female volume. These treatment effects might lead to organizational changes within sexually dimorphic neuroendocrine pathways which, if persistent, could theoretically alter adult reproductive physiology and socio-sexual behavior in rats.

Models that matter: white matter stroke models

Stroke is a devastating neurological disease with limited functional recovery. Stroke affects all cellular elements of the brain and impacts areas traditionally classified as both gray matter and white matter. In fact, stroke in subcortical white matter regions of the brain accounts for approximately 30% of all stroke subtypes, and white matter injury is a component of most classes of stroke damage. However, most basic scientific information in stroke cell death and neural repair relates principally to neuronal cell death and repair. Despite an emerging biological understanding of white matter development, adult function, and reorganization in inflammatory diseases, such as multiple sclerosis, little is known of the specific molecular and cellular events in white matter ischemia. This limitation stems in part from the difficulty in generating animal models of white matter stroke. This review will discuss recent progress in studies of animal models of white matter stroke, and the emerging principles of cell death and repair in oligodendrocytes, axons, and astrocytes in white matter ischemic injury.

Defining the phosphodiesterase superfamily members in rat brain microvessels

Eleven phosphodiesterase (PDE) families are known, each having several different isoforms and splice variants. Recent evidence indicates that expression of individual PDE family members is tissue-specific. Little is known concerning detailed PDE component expression in brain microvessels where the blood-brain-barrier and the local cerebral blood flow are thought to be regulated by PDEs. The present study attempted to identify PDE family members that are expressed in brain microvessels. Adult male F344 rats were sacrificed and blocks of the cerebral cortex and infratentorial areas were dissected. Microvessels were isolated using a filtration method, and total RNA was extracted. RNA quality and quantity were determined using an Agilent bioanalyzer. The isolated cortical and infratentorial microvessel total RNA amounts were 2720 ± 750 ng (n = 2) and 250 ± 40 ng (n = 2), respectively. Microarrays with 22 000 transcripts demonstrated that there were 16 PDE transcripts in the PDE superfamily, exhibiting quantifiable density in the microvessels. An additional immunofluorescent study verified that PDE4D (cAMP-specific) and PDE5A (cGMP-specific) were colocalized with RECA-1 (an endothelial marker) in the cerebral cortex using both F344 rats and Sprague-Dawley rats (n = 3-6/strain). In addition, PDE4D and PDE5A were found to be colocalized with alpha-smooth muscle actin which delineates cerebral arteries and arterioles as well as pericytes. In conclusion, a filtration method followed by microarray analyses allows PDE components to be identified in brain microvessels, and confirmed that PDE4D and PDE5A are the primary forms expressed in rat brain microvessels.

Neuronal precursor cell proliferation in the hippocampus after transient cerebral ischemia: a comparative study of two rat strains using stereological tools

Background

We are currently investigating microglial activation and neuronal precursor cell (NPC) proliferation after transient middle cerebral artery occlusion (tMCAo) in rats. This study aimed: (1) to investigate differences in hippocampal NPC proliferation in outbred male spontaneously hypertensive rats (SHRs) and Sprague-Dawley rats (SDs) one week after tMCAo; (2) to present the practical use of the optical fractionator and 2D nucleator in stereological brain tissue analyses; and (3) to report our experiences with an intraluminal tMCAo model where the occluding filament is advanced 22 mm beyond the carotid bifurcation and the common carotid artery is clamped during tMCAo.

Methods

Twenty-three SDs and twenty SHRs were randomized into four groups subjected to 90 minutes tMCAo or sham. BrdU (50 mg/kg) was administered intraperitoneally twice daily on Day 4 to 7 after surgery. On Day 8 all animals were euthanized. NeuN-stained tissue sections were used for brain and infarct volume estimation with the 2D nucleator and Cavalieri principle. Brains were studied for the presence of activated microglia (ED-1) and hippocampal BrdU incorporation using the optical fractionator.

Results

We found no significant difference or increase in post-ischemic NPC proliferation between the two strains. However, the response to remote ischemia may differ between SDs and SHRs. In three animals increased post-stroke NPC proliferation was associated with hippocampal ischemic injury. The mean infarct volume was 89.2 ± 76.1 mm³ in SHRs and 16.9 ± 22.7 mm³ in SDs (p < 0.005). Eight out of eleven SHRs had ischemic neocortical damage in contrast to only one out of 12 SDs. We observed involvement of the anterior choroidal and hypothalamic arteries in several animals from both strains and the anterior cerebral artery in two SHRs.

Conclusions

We found no evidence of an early hippocampal NPC proliferation one week after tMCAo in both strains. Infarction within the anterior choroidal artery could induce hippocampal ischemia and increase NPC proliferation profoundly. NPC proliferation was not aggravated by the presence of activated microglia. Intraluminal tMCAo in SHRs gave a more reliable infarct with neocortical involvement, but affected territories supplied by the anterior cerebral, anterior choroidal and hypothalamic arteries.

Potential animal models of lacunar stroke: a systematic review

BACKGROUND AND PURPOSE

Lacunar ischemic stroke accounts for 25% of all ischemic strokes, but the exact etiology is unknown. Numerous pathophysiologies have been proposed, including atheroma and endothelial dysfunction. Models of any of these pathological features would aid understanding of the etiology and help develop treatments for lacunar stroke. We therefore aimed to assess the relevance of all available potential animal models of lacunar stroke.

METHODS

We systematically reviewed the published literature for animal models that could represent lacunar stroke using validated search strategies. We included studies that could represent an aspect of lacunar stroke as well as those aiming to model conditions with potentially similar pathology and extracted data on species, induction method, and resulting brain and vessel lesions.

RESULTS

From 5670 papers, 41 studies (46 papers) met inclusion criteria representing over 10 different classes of stroke induction. Important data like infarct size and animal numbers were often missing. Many models' infarcts were too large or affected the cortex. Emboli mostly caused cortical but not small subcortical lesions. Most models focused on creating ischemic lesions in brain tissue. Only one (spontaneous lesions in spontaneously hypertensive stroke-prone rats) also mimicked small vessel pathology. Here, the precursor to small vessel and brain damage was blood-brain barrier failure.

CONCLUSIONS

Some animal models produce small subcortical infarcts, but few mimic the human small vessel pathology. Models of small vessel disease could help improve understanding of human lacunar disease, particularly to clarify factors associated with the small vessel morphological changes preceding brain damage. Much lacunar stroke may arise after blood-brain barrier disruption.

Novel microcatheters for selective intra-arterial injection of fluid in the rat brain

BACKGROUND AND PURPOSE

The internal carotid artery (ICA) in the rat has a single extracranial branch, which supplies the muscles of mastication. The rat ICA also has multiple intracranial branches including (from proximal to distal): multiple small perforating arteries which supply the hypothalamus and the anterior choroidal artery which supplies the choroid plexus and part of the basal ganglia. At the ICA terminus, the vessel bifurcates into the anterior and middle cerebral arteries. The purpose of this study was to demonstrate selective injection of ICA branches in the rat.

MATERIALS AND METHODS

Microcatheters (mucath1 and mucath2) were fabricated by plugging the tip of 169-mum outer diameter polyimide tubing and perforating the sidewalls. A 450-mum polydimethyl-siloxane cylinder was affixed to the distal tip of mucath2 but not mucath1. We evaluated the territory of mucath1 injection ex vivo using magnetization-prepared rapid acquisition of gradient echo MR imaging of brain specimens injected at necropsy. Territories of mucath1 and mucath2 injection were evaluated in vivo with dynamic susceptibility-weighted contrast-enhanced MR imaging. The territory of mucath2 also was evaluated in vivo with fused static microPET/T1 MR images performed after [(18)F] fluorodeoxyglucose ((18)FDG) injection. We evaluated additional catheterized and injected animals at 48 hours using physical examination, T2 MR images, and postmortem brain histologic specimens.

RESULTS

Gadolinium-diethylene-triamine pentaacetic acid (Gd-DTPA) and (18)FDG injected through mucath1 selectively opacified the ipsilateral cerebral hemisphere, with no contralateral opacification. Gd-DTPA injected through mucath2 selectively opacified the territories of the hypothalamic perforating arteries, and anterior choroidal artery. There was no iatrogenic complication 48 hours after 20- to 25-minute injections performed with mucath1 or mucath2.

CONCLUSIONS

We have developed 2 microcatheters which can be placed in the ICA for selective injection of its branches. One microcatheter selectively injects the ipsilateral cerebral hemisphere. The other selectively injects only the hypothalamus and lateral thalamus.

Ischemic stroke in mice and rats

Ischemic stroke occurs most often in the territory of the middle cerebral artery (MCA) in humans. Since its description in rats more than two decades ago, the minimally invasive intraluminal suture occlusion of MCA is an increasingly used model of stroke in both rats and mice due to its ease of inducing ischemia and achieving reperfusion under well-controlled conditions. This method can be used under the guidance of laser-Doppler flowmetry to ascertain the magnitude of occlusion or reperfusion and to decrease the rate of subarachnoid hemorrhage. Ninety minutes of transient ischemia in the territory of MCA results in substantial and reproducible ischemic lesions in both the striatum and the cortex, with characteristics of lesion core and penumbra. Thus, this model is applicable to neuroprotective drug studies, including ischemic brain lesion evaluation (either in vivo with magnetic resonance imaging or post-mortem with brain tissue staining) and neurological status (motor deficits simply assessed by a six-point neurological score scale) as outcome parameters.

A novel method for three-dimensional observation of the vascular networks in the whole mouse brain

A novel method for acquiring serial images suitable for three-dimensional reconstruction of vascular networks in the whole brain of mouse was developed. The brain infused with a White India ink-gelatin solution was fixed and embedded in paraffin containing Sudan Black B through xylene also containing Sudan Black B. Each sliced surface of the paraffin block was coated with liquid paraffin and its image was serially acquired. Coating with liquid paraffin extremely improved the quality of the image. The series of serial images was free of distortion and a three-dimensional image was reconstructed without the problem of the alignment and registration of adjacent images. The volume-rendered image indicated three-dimensional distribution of blood vessels in a whole brain. No ghost or shadow was observed on a volume-rendered image of the White India ink-gelatin infused brain. The z-axial resolution examined on the orthogonal sections reconstituted from serial images obtained at an interval of 5 mum showed no cross talk, indicating that the z-axial resolution was no larger than 5 mum. A proper understanding of the vascular system in a whole brain is indispensable to reveal the development of the vascular system in the brain of normal and genetically manipulated mouse and vascular alterations in pathological situation, such as stroke and neurodegenerative disease. Although simple and inexpensive, this method will provide fundamental information on the vascular system in a whole brain.

Presumed and confirmed striatocapsular brain infarctions in six dogs

OBJECTIVE

To describe the clinical and diagnostic features of the canine sensorimotor syndrome caused by striatocapsular brain infarctions (SCI).

ANIMALS STUDIED

Six dogs with diagnostic imaging or postmortem evidence of SCI.

PROCEDURES

Medical records of dogs with SCI were retrospectively reviewed and the signalment, history, clinical signs, antemortem clinicopathologic test results, diagnostic imaging findings, case outcomes, and pathologic findings recorded.

RESULTS

All dogs had an acute onset of nonprogressive homonymous visual field deficits and contralateral general proprioceptive (GP) deficits. Contralateral hemiparesis and facial hypalgesia were noted in 5/6 dogs. CT scans were normal in 2/4 dogs, and revealed poorly defined hypoattenuating lesions in the subcortical white matter in two dogs. MRI exams were performed in 5/6 dogs and revealed unilateral, variably sized, striatocapsular lesions consistent with nonhemorrhagic infarctions. Diagnostic imaging (6/6) and postmortem examinations (2/6) suggested that SCI resulted from lesions in the vascular territories of the rostral choriodal (6/6) and lenticulostriate arteries (2/6). Diseases predisposing to infarction were not identified in 5/6 dogs. Improvements in mentation, behavior, proprioceptive deficits, and hemiparesis were seen in surviving dogs, but persistent, symptomatic sensory deficits were noted during the follow-up period.

CONCLUSIONS

SCI should be considered as a differential diagnosis for dogs with acute onset, nonprogressive homonymous hemianopia, contralateral GP deficits or hemiparesis, and facial hypalgesia. MRI is the preferred modality for the antemortem imaging diagnosis of SCI. Although partial recovery occurred in all surviving dogs, visual and facial sensory disturbances persisted.

Parecoxib is neuroprotective in spontaneously hypertensive rats after transient middle cerebral artery occlusion: a divided treatment response?

Background

Anti-inflammatory treatment affects ischemic damage and neurogenesis in rodent models of cerebral ischemia. We investigated the potential benefit of COX-2 inhibition with parecoxib in spontaneously hypertensive rats (SHRs) subjected to transient middle cerebral artery occlusion (tMCAo).

Methods

Sixty-four male SHRs were randomized to 90 min of intraluminal tMCAo or sham surgery. Parecoxib (10 mg/kg) or isotonic saline was administered intraperitoneally (IP) during the procedure, and twice daily thereafter. Nineteen animals were euthanized after 24 hours, and each hemisphere was examined for mRNA expression of pro-inflammatory cytokines and COX enzymes by quantitative RT-PCR. Twenty-three tMCAo animals were studied with diffusion and T₂ weighted MRI within the first 24 hours, and ten of the SHRs underwent follow-up MRI six days later. Thirty-three SHRs were given 5-bromo-2'-deoxy-uridine (BrdU) twice daily on Day 4 to 7 after tMCAo. Animals were euthanized on Day 8 and the brains were studied with free-floating immunohistochemistry for activated microglia (ED-1), hippocampal granule cell BrdU incorporation, and neuronal nuclei (NeuN). Infarct volume estimation was done using the 2D nucleator and Cavalieri principle on NeuN-stained coronal brain sections. The total number of BrdU⁺ cells in the dentate gyrus (DG) of the hippocampus was estimated using the optical fractionator.

Results

We found a significant reduction in infarct volume in parecoxib treated animals one week after tMCAo (p < 0.03). Cortical ADC values in the parecoxib group were markedly less increased on Day 8 (p < 0.01). Interestingly, the parecoxib treated rats were segregated into two subgroups, suggesting a responder vs. non-responder phenomenon. We found indications of mRNA up-regulation of IL-1β, IL-6, TNF-α and COX-2, whereas COX-1 remained unaffected. Hippocampal granule cell BrdU incorporation was not affected by parecoxib treatment. Presence of ED-1⁺ activated microglia in the hippocampus was related to an increase in BrdU uptake in the DG.

Conclusion

IP parecoxib administration during tMCAo was neuroprotective, as evidenced by a large reduction in mean infarct volume and a lower cortical ADC increment. Increased pro-inflammatory cytokine mRNA levels and hippocampal granule cell BrdU incorporation remained unaffected.

Role of complement component C5 in cerebral ischemia/reperfusion injury

We evaluated the role of complement component C5 during the course of cerebral ischemic reperfusion injury in a rat model of middle cerebral artery occlusion (MCAO). Systemic C5 inhibition was achieved with an anti-C5 monoclonal antibody, which significantly prevented the deterioration of the motor functions by reducing cerebral lesion and edema. Our results show that activated C5 complement components played an important role in cerebral tissue inflammation resulting from ischemia/reperfusion injury.

The effects of cerebral ischemia on the rat choroid plexus

Although the blood-brain barrier effects of cerebral ischemia have been extensively examined, less attention has focused on ischemia-induced damage to the choroid plexuses that form the blood-cerebrospinal fluid (CSF) barrier (BSCFB). This study examined the rat lateral ventricle choroid plexuses (LVCP) in three ischemic models, bilateral common carotid artery occlusion (2VO)+hypotension with or without reperfusion and permanent middle cerebral artery (MCA) occlusion with or without a tandem common carotid artery occlusion. Blood flow was assessed using [(14)C]-N-isopropyl-p-iodoamphetamine, and LVCP injury by tissue edema, alterations in [(14)C]glutamine transport and BSCFB disruption (measured with [(3)H]inulin). 2VO+hypotension caused an 87% reduction in LVCP blood flow (P<0.01) and a progressive reduction in LVCP glutamine transport. In contrast to cortex, there was no LVCP hyperemia or delayed hypoperfusion on reperfusion, but there was marked BSCFB disruption. After 30 mins of 2VO+hypotension with 6 h of reperfusion, the [(3)H]inulin entry into CSF was increased threefold (P<0.05). Blood-CSF barrier rather than blood-brain barrier disruption appeared to be the main cause of enhanced [(3)H]inulin entry into hippocampus. Middle cerebral artery occlusion with and without a tandem common carotid artery occlusion only caused 53% and 38% reductions in LVCP blood flow but induced LVCP edema. Results suggest that the LVCP is selectively vulnerable to ischemic injury in terms of the absolute blood flows or, for the MCA occlusion models, the % reductions in flows required to induce injury. BCSFB disruption early after ischemia may enhance the movement of compounds from blood to areas close to the ventricular system and participate in delayed neuronal death.