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- Andin, Josefine, 1979-, et al.
(author)
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Influence of environmental enrichment on steady-state mRNA levels for EAAC1, AMPA1 and NMDA2A receptor subunits in rat hippocampus
- 2007
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In: Brain Research. - : Elsevier BV. - 0006-8993 .- 1872-6240. ; 1174:1, s. 18-27
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Journal article (peer-reviewed)abstract
- Interaction with the environment has a key role in refining the neuronal circuitry required for normal brain function throughout life. Profound effects of enriched environment have been shown on neuronal structure and chemistry in experimental animals. Epidemiological studies imply that this is true also in man, thus cognitive stimulation has a protective effect on neurodegeneration, e.g., in Alzheimer's disease. Glutamatergic pathways are imperative for cognitive functions, such as memory, learning and long-term potentiation, and relies on the AMPA and NMDA glutamate receptors and the hippocampus, with its specific subregions, is an important anatomical substrate in this. The glutamate signalling is also dependent on a fine-tuned transport system, in the hippocampus primarily achieved by the glutamate transporter EAAC1. In this study we show how environmental enrichment modulates these parts of the glutamatergic system using quantitative in situ hybridisation. This work demonstrates for the first time that environmental enrichment modulates the mRNA expression of EAAC1 which is significantly and region specifically decreased in the hippocampus. We also provide evidence for regional and hemisphere-specific upregulation of NMDA mRNA in the hippocampus after environmental enrichment. The current work also shows that AMPA mRNA of the hippocampus is not per se changed by environmental enrichment in adult animals. Taken together, our results extend the knowledge of the glutamatergic system of specific regions of the hippocampus and its modulation by environmental enrichment and could contribute to the development of strategies aimed at limiting pathological changes associated with glutamatergic dysfunctions. © 2007.
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- Andin, Josefine, 1979-
(author)
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Pharmacological and environmental modulations of the rat glutamatergic system
- 2006
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Licentiate thesis (other academic/artistic)abstract
- Glutamate is the principal excitatory neurotransmitter in the central nervous system and it is implicated in neural transmission, learning, memory processes and neuronal plasticity. In the glutamatergic synapse two main components are present; the glutamate receptors and the glutamate transporters. The receptors, the NMDA, AMPA, kainite and the metabotroptic receptors, are responsible for conveying neural transmission, including long term potentiation (LTP), synaptic strengthening and modification. The transporters, located to the neuronal membrane and to the membranes of surrounding astrocytes, regulates the extracellular concentration of glutamate and thereby the duration of the synaptic signal.Alterations in both receptor and transporter systems have been suggested to be important in the pathogenesis of several acute and chronic nervous system diseases, such as psychosis, mood disorders, epilepsy, Parkinson's disease and Alzheimer's disease. The pathophysiology of these disorders is not yet completely understood and the involvement of glutamate is unclear. In this thesis we have sought to investigate the role of the glutamatergic system in the treatment of mood disorders and dementia. The antidepressant drug amitriptyline exerts its main effects on the serotonergic and noradrenergic systems and the antidementia drug rivastigmine acts mainly on the cholinergic system. However, given the close relationship between different neurotransmitter systems we have investigated the influence of amitriptyline and rivastigmine on the mRNA expression of the neuronal transporter, EAAC1, in rats. The results showed for the first time an involvement of EAAC1 in amitriptyline and rivastigmine treatment. Amitriptyline induced an acute increase in EAAC1 mRNA expression, which 24 hour after administration returned to baseline levels. Chronic treatment, on the other hand, induces a significant decrease in cortical areas, which we suggest results in enhanced neuronal transmission. Rivastigmine treatment, acute as well as chronic, induced increases in the mRNA expression in hippocampus. We hypothesize that this counteracts the excitotoxic glutamate levels seen in Alzheimer's disease.Further, environmental enrichment has been shown to have beneficial effects on capillary supply, the number of glial cells and dendritic spines, the thickness and weight of cortex, the concentration of cholinesterase, LTP and synaptic strength in animals. It has also been reported that humans that lead an active life have a reduced risk of developing Alzheimer's disease. This suggests that an active and stimulated life may have a protective effect against dementia in man, by creating a cognitive reserve which provides a buffer against brain pathology or age-related changes. We investigated the influence of environmental enrichment on the mRNA expression of NMDA and AMPA receptors and on EAACl and showed for the first time that EAAC1 mRNA is decreased after environmental enrichment. This is probably followed by an increase of glutamate in the synapse, which in turn leads to enhanced neuronal transmission including enhanced memory formation and learning. Furthermore, we confirmed in greater detail previous findings on the upregulation of NMDA mRNA and show that the regulation is regionally and hemisphere specific. We also confirm that AMPA mRNA is not per se changed by environmental enrichment in adult animals.This work provides further evidence about the involvement of the glutamatergic system in affective and cognitive disorders. Improved knowledge of the glutamatergic system will contribute to the development of strategies aimed at limiting pathological changes associated with glutamatergic dysfunctions.
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- Andin, Josefine, 1979-, et al.
(author)
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Rivastigmine as a Modulator of the Neuronal Glutamate Transporter rEAAC1 mRNA Expression
- 2005
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In: Dementia and Geriatric Cognitive Disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 19:1, s. 18-23
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Journal article (peer-reviewed)abstract
- Alzheimer’s disease is a neurodegenerative disorder that affects the cholinergic, glutamatergic and monoaminergic systems in the neocortex and hippocampus. Today, the major pharmacological treatment involves the use of acetylcholinesterase inhibitors (AChEIs). In this study, an in situ hybridisation technique (using digoxigenin-labelled cRNA probes) was used to elucidate changes in mRNA expression of the neuronal glutamate transporter, rat excitatory amino carrier 1 (rEAAC1), after treatment with the AChEI rivastigmine. Compared with saline-treated rats, the rats subchronically (3 days) and chronically (21 days), but not acutely, treated with rivastigmine showed a significant increase in rEAAC1 mRNA expression in the hippocampal areas cornu anterior 1 (CA1), CA2, CA3 and dentate gyrus (p < 0.01), but not in the cortical areas. These results provide the first evidence that the glutamatergic system is modulated following acetylcholinesterase inhibition by rivastigmine, a finding, which is likely to be of importance for the clinical effects.
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- Rudner, Mary, 1958-, et al.
(author)
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Differences in temporal and spatial processing mechanisms in working memory for signed and spoken language
- 2009
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In: The 11th European congress of Psychology, Oslo, Norway, 7-10 July 2009.,2009.
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Conference paper (peer-reviewed)abstract
- Objectives Working memory (WM) capacity is similar for signed (SL) and spoken (SpL) language yet underlying temporal and spatial processing mechanisms may not be identical. To investigate this, two studies with deaf native signers (DS) and hearing non-signers (HN) were conducted. Methods DS and matched HN groups performed WM tasks with varying temporal and spatial demands in study 1 at encoding (temporal, spatial and mixed presentation styles) and in study 2 at retrieval (forward and backward span) and with abstract spatial demands (math span). Results DS performance was inferior with high temporal demands at encoding (temporal style) and retreival (forward span). There was no difference between groups with high spatial order demands at encoding (spatial style) or retrieval (backward span). DS performance was worse when abstract spatial processing was involved (math span). Conclusion WM processing mechanisms for SL and SpL differ for temporal information at encoding and retrieval and for abstract spatial information.
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