Environmental enrichment improves functional and neuropathological indices following stroke in young and aged rats.
ABSTRACT Aging is associated with a temporally dysregulated cellular response to ischemia as well as poor functional recovery. While environmental enrichment has been shown to improve the behavioral outcome of stroke in young animals, the effect of an enriched environment on behavioral and neuropathological recovery in aged animals is not known.
Focal cerebral ischemia was produced by electrocoagulation of the right middle cerebral artery in 3 month- and 20 month-old male Sprague-Dawley rats. The functional outcome was assessed in neurobehavioral tests conducted over a period of 28 days following surgery. Brain tissue was then immunostained for proliferating astrocytes and the infarct and scar tissue volumes were measured.
Aged rats showed more severe behavioral impairments and diminished functional recovery compared to young rats. Most infarcted animals had disturbances of sensorimotor function, with recovery beginning later, progressing more slowly, and reaching a lower functional endpoint in aged animals. However, the enriched environment significantly improved the rate and extent of recovery in aged animals. Correlation analysis revealed that the beneficial effect of the enriched environment on recovery, both in young and aged rats, correlated highly with a reduction in infarct size, in the number of proliferating astrocytes, and in the volume of the glial scar.
These results suggest that temporally modulating astrocytic proliferation and the ensuing scar formation might be a fruitful approach to improving functional recovery after stroke in aged rats.
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ABSTRACT: Environmental enrichment provides laboratory animals with novelty and extra space, allowing different forms of multisensory stimulation ranging from social grouping to enhanced motor activity. At the extreme end of the spectrum, one can have a super-enriched environment. Environmental enrichment is believed to result in improved cognitive and sensorimotor functions both in naïve rodents and in animals with brain lesions such as those occurring after a stroke. Robust behavioral effects in animals which have suffered a stroke are probably related not only to neuronal plasticity in the perilesional cortex but also in remote brain areas. There is emerging evidence to suggest that testing restorative therapies in an enriched environment can maximize treatment effects, e.g., the perilesional milieu seems to be more receptive to concomitant pharmacotherapy and/or cell therapy. This review provides an updated overview on the effect of an enriched environment in stroke animals from the practical points to be considered when planning experiments to the mechanisms explaining why combined therapies can contribute to behavioral improvement in a synergistic manner.Frontiers in Neuroscience 03/2015; 9:106. DOI:10.3389/fnins.2015.00106
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ABSTRACT: The naturally occurring polyphenol phytoalexin resveratrol (RSV) regulates neuronal inflammation in various disease models and protects the brain against ischemic injury. Cell surface glutamate transporters on perisynaptic astrocytes are important regulators of extracellular glutamate levels and synaptic activation. Following cerebral ischemia, reduced astroglial type-1 glutamate transporter (GLT-1) expression in the CA1 pyramidal layers of the hippocampus contribute to neurotoxic glutamate levels. The current study examined the effects of 21-day RSV pretreatment (1 or 10mg/kg dose; i.p.) on microglia and astrocyte activation and characterized GLT-1 expression in the dentate gyrus (DG), CA1 and CA3 layers of the hippocampus 7 days following 10min global ischemia. Male Wistar rats were divided into five groups; sham/saline, ischemia/saline, ischemia/1mg/kg RSV, ischemia/10mg/kg RSV and sham/10mg/kg RSV. Immunohistochemical detection of GLT-1, CD11b/c, glial fibrillary acidic protein (GFAP) assessed type 1 glutamate transporter expression and microglial/glial cell activation following sham surgery or global ischemia. Our findings demonstrate prevention by RSV of ischemia-induced reduction of GLT-1 expression in the vulnerable CA1 layer 7 days following global ischemia, which was accompanied by the polyphenol's inhibition of post ischemic increase in CD11b/c and GFAP expression. RSV also conferred significant CA1 neuronal protection positively correlated with attenuation of glutamate transporter activation. These findings support beneficial effects of RSV in modulation of the excitotoxic cascade postischemia, which are congruent with anti-inflammatory effects observed in various pathological models. Copyright © 2015. Published by Elsevier B.V.Brain Research 02/2015; DOI:10.1016/j.brainres.2015.02.038 · 2.83 Impact Factor
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ABSTRACT: Constraint-induced movement therapy (CIMT) after stroke enhances not only functional reorganization but also structural plasticity of the brain in the adult rats. We examined whether forced limb-use which mimicked CIMT could influence ischemia-induced neurogenesis, apoptosis and behavioral recovery in the aged rats. Aged rats were divided into a sham group, an ischemia group, and an ischemia group with forced limb-use. Focal cerebral ischemia was induced by injection of endothelin-1. Forced limb-use began on post-stroke day 7 by fitting a plaster cast around the unimpaired upper limbs of rats for 3 weeks. Behavioral recovery was evaluated by tapered/ledged beam-walking test on postoperative day 32. The expression of doublecortin (DCX), neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP) and Iba-1 were measured by single or double immunohistochemistry, and apoptosis was measured by TUNEL assay. The production of neuroblasts in the subventricular zone (SVZ) was significantly increased after stroke. Forced limb-use enhanced the proliferation of newborn neurons in the SVZ, as well as increased the long-term survival of newborn neurons. Furthermore, forced limb-use suppressed apoptosis and improved the motor functions after stroke in the aged rats. Forced limb-use exerted few effects on inflammation. Neither the number nor dendritic complexity of newborn granule cells in the hippocampus was affected by forced limb-use. Forced limb-use is effective in enhancing neurogenesis and behavioral recovery after stroke even in the aged rats. Copyright © 2014. Published by Elsevier Ltd.Neuroscience 11/2014; 286. DOI:10.1016/j.neuroscience.2014.11.040 · 3.33 Impact Factor