IntroductionCerebral small vessel disease (cSVD) is one of the most prevalent neurological disorders. The progressive remodeling of brain microvessels due to arterial hypertension or other vascular risk factors causes subtle, but constant cognitive decline through to manifest dementia and substantially increases the risk for stroke. Preliminary evidence suggests the contribution of the immune system to disease initiation and progression, but a more detailed understanding is impaired by the unavailability of appropriate animal models. Here, we introduce the spontaneously hypertensive rat (SHR) as a model for early onset cSVD and unveiled substantial immune changes in conjunction with brain abnormalities that resemble clinical findings.ResultsIn contrast to age-matched normotensive Wistar Kyoto (WKY) rats, male SHR exhibited non-spatial memory deficits. Magnetic resonance imaging showed brain atrophy and a reduction of white matter volumes in SHR. Histological analyses confirmed white matter demyelination and unveiled a circumscribed blood brain barrier dysfunction in conjunction with micro- and macrogliosis in deep cortical regions. Flow cytometry and histological analyses further revealed substantial disparities in cerebral CD45high leukocyte counts and distribution patterns between SHR and WKY. SHR showed lower counts of T cells in the choroid plexus and meningeal spaces as well as decreased interleukin-10 levels in the cerebrospinal fluid. On the other hand, both T and NK cells were significantly augmented in the SHR brain microvasculature.ConclusionsOur results indicate that SHR share behavioral and neuropathological characteristics with human cSVD patients and further undergird the relevance of immune responses for the initiation and progression of cSVD.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0169-8) contains supplementary material, which is available to authorized users.

Background and Purpose-In aged humans, stroke is a major cause of disability for which no neuroprotective measures are available. Granulocyte-colony stimulating factor (G-CSF), a member of the cytokine family of growth factors, promotes brain neurogenesis and improves functional outcome after stroke in young animals. We tested the hypothesis that G-CSF provides a restorative therapeutic benefit in aged animals. Methods-Focal cerebral ischemia was produced by reversible occlusion of the right middle cerebral artery in 19-to 20-month-old male Sprague-Dawley rats. One hour after reperfusion, the aged rats were treated daily with 15 g/kg G-CSF and for 15 days total. Rats were behaviorally tested and the brains removed for analysis at 28 days poststroke. Results-G-CSF treatment after stroke exerted a robust and sustained beneficial effect on survival rate and running function. Transient improvement after G-CSF treatment could be observed for coordinative motor function on the inclined plane test and for working memory in the radial-arm maze test. At the cellular level, G-CSF treatment increased the number of proliferating cells in the subventricular zone and dentate gyrus and also increased the number of newborn neurons in the subventricular zone ipsilateral to the lesion. Conclusions-These results suggest that G-CSF treatment in aged rats has a survival-enhancing capacity and a beneficial effect on functional outcome, most likely through supportive cellular processes such as neurogenesis.

Background and Purpose-Both application of neurotrophic factors like brain-derived neurotrophic factor (BDNF) and constraint-induced movement therapy like forced arm use have been shown to potentially improve outcome after stroke. The aim of the present study was to check whether postischemic long-term outcome correlates to specific modifications in the abundance of various neurotransmitter receptors. Methods-Adult male Wistar rats were subjected to photothrombotic ischemia and assigned to various treatment groups (nϭ5 each) with end points at 3 and 6 weeks: (1) ischemic control (saline); (2) BDNF (ischemia, 20 g BDNF); (3) forced arm use (ischemia, saline, and ipsilateral plaster cast for 5 or 14 days for the 3-and 6-week groups, respectively); and (4)

Granulocyte-colony stimulating factor (G-CSF) is a hematopoietic growth factor that controls proliferation and differentiation of neural stem cells. Although recent studies have begun to explore G-CSF-related mechanisms of action in various disease models, little is known about its function in the healthy brain. In the present study, the effect of G-CSF deficiency on memory formation and motor skills was investigated. The impact of G-CSF deficiency on the structural integrity of the hippocampus was evaluated by analyzing the generation of doublecortin-expressing cells, the amount of bromodeoxyurine-labeled cells, the dendritic complexity in hippocampal neurons, the binding densities of NMDA and GABA A receptors and the induction of long-term potentiation (LTP). G-CSF deficiency caused a disruption in memory formation and in the development of motor skills. These impairments were associated with reduced ligand binding densities of NMDA receptors in hippocampal subfields CA3 and the dentate gyrus. The reduced excitation was potentiated by increased ligand binding densities of GABA A receptors resulting in a relative shift in favor of inhibition and impaired behavioral performance. These alterations were accompanied by impaired induction of LTP in the CA1 region. Moreover, G-CSF deficiency led to decreased dendritic complexity in hippocampal neurons in the dentate gyrus and the CA1 region. G-CSF deficiency also caused a reduction of neuronal precursor cells in the dentate gyrus. These findings confirm G-CSF as an essential neurotrophic factor, and point to a role in the proliferation, differentiation and functional integration of neural cells necessary for the structural and functional integrity of the hippocampal formation.

Endogenous dopamine plays a central role in salience coding during associative learning. Administration of the dopamine precursor levodopa enhances learning in healthy subjects and stroke patients. Because levodopa increases both phasic and tonic dopaminergic neurotransmission, the critical mechanism mediating the enhancement of learning is unresolved. We here probed how selective tonic dopaminergic stimulation affects associative learning. Forty healthy subjects were trained in a novel vocabulary of 45 concrete nouns over the course of 5 consecutive training days in a prospective, randomized, double-blind, placebo-controlled design. Subjects received the tonically stimulating dopamine-receptor agonist pergolide (0.1 mg) vs placebo 120 min before training on each training day. The dopamine agonist significantly impaired novel word learning compared to placebo. This learning decrement persisted up to the last follow-up 4 weeks post-training. Subjects treated with pergolide also showed restricted emotional responses compared to the PLACEBO group. The extent of 'flattened' affect with pergolide was related to the degree of learning inhibition. These findings suggest that tonic occupation of dopamine receptors impairs learning by competition with phasic dopamine signals. Thus, phasic signaling seems to be the critical mechanism by which dopamine enhances associative learning in healthy subjects and stroke patients.

Background and Purpose-Although several studies have shown beneficial effects of training in animal stroke models, the most effective training strategy and the optimal time to initiate training have not been identified. The present metaanalysis was performed to compare the efficacy of different training strategies and to determine the optimal time window for training in animal stroke models. Methods-We searched the literature for studies analyzing the efficacy of training in animal models of ischemic stroke.Training was categorized into forced physical training, voluntary physical training, constraint-induced movement therapy, and skilled reaching training. Two reviewers independently extracted data on study quality, infarct size, and neurological outcome. Data were pooled by means of a meta-analysis. Results-Thirty-five studies with >880 animals were included. A meta-analysis of all treatments showed that training reduced the infarct volume by 14% (95% confidence interval, 2%-25%) and improved the cognitive function by 33% (95% confidence interval, 8%-50%), the neuroscore by 13.4% (95% confidence interval, 1.5%-25.3%), and the running function by 6.6% (95% confidence interval, 1.4%-11.9%). Forced physical training reduced the infarct volume and enhanced the running function most effectively, whereas skilled reaching training improved the limb function most effectively. A meta-regression illustrated that training was particularly efficacious when initiated between 1 and 5 days after stroke onset. Conclusions-Our meta-analysis confirms that training reduces the infarct volume and improves the functional recovery in animal stroke models. Forced physical training and skilled reaching training were identified as particularly effective training strategies. The efficacy of training is time dependent. (Stroke. 2014;45:239-247.)

Background and Purpose-The neuroprotective potential of citicoline in acute ischemic stroke has been shown in many experimental studies and, although the exact mechanisms are still unknown, a clinical Phase III trial is currently underway. Our present study was designed to check whether citicoline also enhances neuroregeneration after experimental stroke. Methods-Forty Wistar rats were subjected to photothrombotic stroke and treated either with daily injections of citicoline (100 mg/kg) or vehicle for 10 consecutive days starting 24 hours after ischemia induction. Sensorimotor tests were performed after an adequate training period at Days 1, 10, 21, and 28 after stroke. Then brains were removed and analyzed for infarct size, glial scar formation, neurogenesis, and ligand binding densities of excitatory and inhibitory neurotransmitter receptors. Results-Animals treated with citicoline showed a significantly better neurological outcome at Days 10, 21, and 28 after ischemia, which could not be attributed to differences in infarct volumes or glial scar formation. However, neurogenesis in the dentate gyrus, subventricular zone, and peri-infarct area was significantly increased by citicoline. Furthermore, enhanced neurological outcome after citicoline treatment was associated with a shift toward excitation in the perilesional cortex. Conclusions-Our present data demonstrate that, apart from the well-known neuroprotective effects in acute ischemic stroke, citicoline also possesses a substantial neuroregenerative potential. Thanks to its multimodal effects, easy applicability, and history as a well-tolerated drug, Key Words: citicoline Ⅲ neurogenesis Ⅲ receptor autoradiography Ⅲ regeneration Ⅲ stroke A lthough most patients with stroke show some degree of spontaneous functional improvement, 1 recovery is generally far from complete. Therefore, there is an urgent need to identify therapeutic strategies to support endogenous poststroke repair mechanisms. One candidate stroke drug for ischemic stroke with an extended therapeutic window, which is currently under investigation in a randomized, doubleblind, placebo-controlled, multicenter clinical Phase III trial (International Citicoline Trial on Acute Stroke [ICTUS]), is citicoline (also known as cytidine-5-diphosphocholine or CDP-choline). Although citicoline seems to display a multitude of beneficial effects, the exact mechanisms of action are still enigmatic.Citicoline, a naturally occurring endogenous compound, is an essential intermediate in the biosynthesis of phosphatidylcholine. 2 Citicoline has been shown to have neuroprotective effects in a variety of central nervous system injury models, including cerebral ischemia. [3][4][5][6] The suggested mechanisms that may explain the neuroprotective actions of citicoline include prevention of fatty acid release, 7 stimulation of phosphatidylcholine synthesis, 2 preservation of cardiolipin and sphingomyelin levels, 7 increase of glutathione synthesis and glutathione reductase activity, 8 restoration of Na ϩ /K ϩ -ATPase ac...

Targeting different monocyte/macrophage subsets has no impact on outcome after ischemic stroke in mice. Altogether, our study could not identify monocytes/macrophages as relevant therapeutic targets in acute ischemic stroke.