| 1. |
- Dahlqvist, Per, et al.
(författare)
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Environmental enrichment reverses learning impairment in the Morris water maze after focal cerebral ischemia in rats
- 2004
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Ingår i: European Journal of Neuroscience. - 0953-816X .- 1460-9568. ; 19:8, s. 2288-2298
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Tidskriftsartikel (refereegranskat)abstract
- Cognitive impairment is common after ischemic stroke. In rodent stroke models using occlusion of the middle cerebral artery (MCA) this is reflected by impaired spatial memory associated with the size of the ischemic lesion. Housing in an enriched environment enhances brain plasticity and improves recovery of sensorimotor functions after experimental stroke in rats. In this study we report that postischemic housing in an enriched environment also attenuates the long-term spatial memory impairment after MCA occlusion and extinguishes the association between spatial memory and infarct volume. An enriched environment did not significantly alter the expression of selected neuronal plasticity-associated genes 1 month after MCA occlusion, indicating that most of the adaptive changes induced by an enriched environment have already occurred at this time point. We conclude that the attenuated memory impairment induced by environmental enrichment after MCA occlusion provides a useful model for further studies on the neurobiological mechanisms of recovery of cognitive functions after ischemic stroke.
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| 2. |
- George, Sonia, et al.
(författare)
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Lesion of the subiculum reduces the spread of amyloid beta pathology to interconnected brain regions in a mouse model of Alzheimer's disease.
- 2014
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Ingår i: Acta Neuropathologica Communications. - : Springer Science and Business Media LLC. - 2051-5960. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- The progressive development of Alzheimer's disease (AD) pathology follows a spatiotemporal pattern in the human brain. In a transgenic (Tg) mouse model of AD expressing amyloid precursor protein (APP) with the arctic (E693G) mutation, pathology spreads along anatomically connected structures. Amyloid-β (Aβ) pathology first appears in the subiculum and is later detected in interconnected brain regions, including the retrosplenial cortex. We investigated whether the spatiotemporal pattern of Aβ pathology in the Tg APP arctic mice to interconnected brain structures can be interrupted by destroying neurons using a neurotoxin and thereby disconnecting the neural circuitry.
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| 3. |
- Hedskog, Louise, et al.
(författare)
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Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models
- 2013
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 110:19, s. 7916-7921
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Tidskriftsartikel (refereegranskat)abstract
- It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer's disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containing familial presenilin-2 AD mutation. The effect of AD pathogenesis on the ER-mitochondria interplay in the brain has so far remained unknown. Here, we studied ER-mitochondria contacts in human AD brain and related AD mouse and neuronal cell models. We found uniform distribution of MAM in neurons. Phosphofurin acidic cluster sorting protein-2 and sigma 1 receptor, two MAM-associated proteins, were shown to be essential for neuronal survival, because siRNA knockdown resulted in degeneration. Up-regulated MAM-associated proteins were found in the AD brain and amyloid precursor protein (APP)(Swe/Lon) mouse model, in which up-regulation was observed before the appearance of plaques. By studying an ER-mitochondria bridging complex, inositol-1,4,5-triphosphate receptor-voltage-dependent anion channel, we revealed that nanomolar concentrations of amyloid beta-peptide increased inositol-1,4,5-triphosphate receptor and voltage-dependent anion channel protein expression and elevated the number of ER-mitochondria contact points and mitochondrial calcium concentrations. Our data suggest an important role of ER-mitochondria contacts and cross-talk in AD pathology.
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| 4. |
- Hu, Xiao-Lei, et al.
(författare)
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Enriched environment increases spinophilin mRNA expression and spinophilin immunoreactive dendritic spines in hippocampus and cortex
- 2010
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Ingår i: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 476:2, s. 79-83
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Tidskriftsartikel (refereegranskat)abstract
- Housing rodents in an enriched environment (EE) induces structural and functional plasticity in the adult brain, including increased dendritic sprouting and number of dendritic spines. However, the molecular mechanisms behind EE-induced brain plasticity remain largely unknown. Circadian rhythm plays an important role in memory processing but the neurobiological mechanisms of how circadian rhythm affects memory and brain plasticity remain controversial. In the current study, we studied the expression of spinophilin, a protein highly enriched in dendritic spines and involved in spine morphology and synaptic plasticity, to examine the effects of EE and circadian rhythm in rats housed in EE for different periods of time. Spinophilin mRNA expression was studied by in situ hybridization and the density of spinophilin immunoreactive puncta was quantified after immunohistochemical staining. Compared to rats living in a deprived environment (DE), we found a transient increase in the density of spinophilin immunoreactive puncta in hippocampus and cortex after 1 week of EE housing and persistent elevations of spinophilin mRNA expression during 1-4 weeks of environmental enrichment. Increased spinophilin expression was found during the light phase of the diurnal cycle, but not the dark phase. Thus, enriched housing altered the diurnal variation in spinophilin mRNA expression, suggesting that circadian modulation is likely to be important for experience dependent plasticity. The current results suggest a possible role for spinophilin in neuronal plasticity induced by environmental enrichment, but further studies are needed to establish a cause-effect relation.
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| 5. |
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| 6. |
- Rönnbäck, Annica, et al.
(författare)
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Diurnal effects of enriched environment in immediate early gene expression in the rat brain
- 2005
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Ingår i: Brain research. - : Elsevier BV. - 0006-8993. ; 1046:1-2, s. 137-144
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Tidskriftsartikel (refereegranskat)abstract
- Rodents housed in an enriched environment (EE) show increased neuronal plasticity with enhanced long-term potentiation and memory performance. We report an EE-induced increase in NGFI-A and Krox-20 mRNA expression exclusively during the dark period of the day. In addition, EE-housed rats showed considerable diurnal variation in NGFI-A, Krox-20, and NGFI-B mRNA expression which was absent in single-housed rats. Thus, EE-induced molecular changes are more evident during the dark phase when the rats have higher motor and exploratory activity. This is important to take into account in future studies of molecular mediators of experience-dependent neuronal plasticity.
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| 7. |
- Rönnbäck, Annica, et al.
(författare)
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Gene expression profiling of the rat hippocampus one month after focal cerebral ischemia followed by enriched environment
- 2005
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Ingår i: Neuroscience Letters. - : Elsevier BV. - 0304-3940 .- 1872-7972. ; 385:2, s. 173-178
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Tidskriftsartikel (refereegranskat)abstract
- Functional recovery after experimental stroke in rats is enhanced by environmental enrichment by stimulating plastic changes in brain regions outside the lesion, but the molecular mechanisms are not known. We investigated the effect of environmental enrichment after focal cerebral ischemia on cognitive recovery and hippocampal gene expression using microarray analysis. Rats placed in enriched environment (EE) for 1 month after middle cerebral artery occlusion (MCAo) showed significantly improved spatial memory in the Morris water maze compared to rats housed alone after MCAo. Microarray analysis suggested several EE-induced differences in neuronal plasticity-related genes, but these changes could not be confirmed by quantitative real-time PCR. This study highlights some of the potential problems associated with gene expression profiling of brain tissues. Further studies at earlier time points and in additional subregions of the brain are of interest in the search for molecular mechanisms behind EE-induced neuronal plasticity after ischemic stroke.
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| 8. |
- Rönnbäck, Annica, 1974-
(författare)
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The effect of enriched environment on gene expression and stroke recovery
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stroke is the third leading cause of death and the major course of long-term disabilities in industrialized countries. Most surviving stroke patients show some degree of spontaneous recovery, but persistent symptoms in sensorimotor and cognitive functions are common. The symptoms can be reproduced in experimental stroke models in rats by occlusion of the middle cerebral artery. Housing rats in an enriched environment (EE), i.e. group housing in a large cage with toys that are changed daily, increases neuronal plasticity in healthy rats and can also improve functional recovery after experimental stroke. The present thesis investigates the effect of EE on the recovery of sensorimotor and cognitive functions one month after focal cerebral ischemia in rats, with emphasis on the underlying molecular mechanisms. Furthermore, EE-induced effect on gene expression in healthy rats was investigated after different periods of EE-housing and at different time points of the day. We show an improved recovery of both sensorimotor and cognitive functions in rats housed in EE for one month after focal cerebral ischemia. The recovery of sensorimotor function correlated significantly to mRNA expression of the plasticity associated transcription factors NGFI-A and NGFI-B in hippocampus and cortical regions outside the infarct. Social interaction seems to be an important component for the beneficial effects of EE after focal cerebral ischemia. Microarray analysis of hippocampal gene expression after one month of postischemic environmental enrichment revealed no confirmable EE-induced changes that could explain the improved recovery in spatial memory. Interestingly, healthy rats housed in EE showed increased mRNA expression of NGFI-A and Krox-20 exclusively during the dark period of the day compared to rats housed in isolation. In addition, EE housed rats had a substantial diurnal variation in NGFI-A, Krox-20 and NGFI-B mRNA expression; this was absent in single-housed rats. EE-induced changes in gene expression are more evident during the dark period of the day, when rats are more active and can benefit from the stimulating environment. This is important to consider in future investigation of putative mediators of the EE-induced neuronal plasticity. In summary, these findings may contribute to an increased understanding of the underlying molecular mechanisms behind improved functional recovery in rats housed in enriched environment after focal cerebral ischemia.
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