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Fluoxetine, a selective serotonin-reuptake inhibitor (SSRI), is known to induce structural rearrangements and changes in synaptic transmission in hippocampal circuitry. In the adult hippocampus, structural changes include neurogenesis, dendritic, and axonal plasticity of pyramidal and dentate granule neurons, and dedifferentiation of dentate granule neurons. However, much less is known about how chronic fluoxetine affects these processes along the septotemporal axis and during the aging process. Importantly, studies documenting the effects of fluoxetine on density and distribution of spines along different dendritic segments of dentate granule neurons and CA1 pyramidal neurons along the septotemporal axis of hippocampus in adulthood and during aging are conspicuously absent. Here, we use a transgenic mouse line in which mature dentate granule neurons and CA1 pyramidal neurons are genetically labeled with green fluorescent protein (GFP) to investigate the effects of chronic fluoxetine treatment (18 mg/kg/day) on input-specific spine remodeling and mossy fiber structural plasticity in the dorsal and ventral hippocampus in adulthood and middle age. In addition, we examine levels of adult hippocampal neurogenesis, maturation state of dentate granule neurons, neuronal activity, and glutamic acid decarboxylase-67 expression in response to chronic fluoxetine in adulthood and middle age. Our studies reveal that while chronic fluoxetine fails to augment adult hippocampal neurogenesis in middle age, the middle-aged hippocampus retains high sensitivity to changes in the dentate gyrus (DG) such as dematuration, hypoactivation, and increased glutamic acid decarboxylase 67 (GAD67) expression. Interestingly, the middle-aged hippocampus shows greater sensitivity to fluoxetine-induced input-specific synaptic remodeling than the hippocampus in adulthood with the stratum-oriens of CA1 exhibiting heightened structural plasticity. The input-specific changes and circuit-level modifications in middle-age were associated with modest enhancement in contextual fear memory precision, anxiety-like behavior and antidepressant-like behavioral responses.
Pubmed ID: 25850664 RIS Download
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An independent, nonprofit organization focused on mammalian genetics research to advance human health. Their mission is to discover the genetic basis for preventing, treating, and curing human disease, and to enable research for the global biomedical community. Jackson Laboratory breeds and manages colonies of mice as resources for other research institutions and laboratories, along with providing software and techniques. Jackson Lab also conducts genetic research and provides educational material for various educational levels.
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These Brainbow 1.0 (founder line L) mice allow labeling of individual neuronal types (specifically hippocampal neuron cell bodies, and including motor neurons, dentate gyrus granule cells, pyramidal neurons of the cortex and CA1 area) with approximately 166 distinguishable color variations in cre recombined cells, and may also be useful in conjunction with other Brainbow strains (Stock No. 007901, Stock No. 007911, Stock No. 007921) for neurobiological studies. These Thy1-Brainbow 1.0 (line L) transgenic mice are viable and fertile. The mice possess multiple fluorescent protein sequences uniquely flanked with pairs of incompatible Lox sites alternated to create mutually exclusive recombination events; allowing stochastic expression of multiple fluorescent proteins from a single transgene. Prior to Cre-mediated recombination, the fluorescent protein immediately adjacent to the promoter, dTomato (RFP), is expressed in peripheral and central neurons. When bred to Cre recombinase expressing mice, the resulting offspring can have one of three expression outcomes for each transgene in each cell of the cre expressing tissue(s): dTomato (RFP) (no recombination), mCerulean (CFP), or mYFP. Integration of tandem transgene copies yields combinatorial fluorescent protein expression in each cell, and thus many possible cell colors, providing a way to distinguish adjacent neurons and visualize other cellular interactions. Of note, the single FRT site inserted in the transgene allows tandem transgene copy number reduction through Flp-mediated recombination if desired. These Brainbow 1.0 (founder line L) mice were found to have multiple transgene copies that allow labeling of individual neuronal types (specifically hippocampal neuron cell bodies, and including motor neurons, dentate gyrus granule cells, pyramidal neurons of the cortex and CA1 area) with approximately 166 distinguishable color variations in cre recombined cells, and may also be useful in conjunction with other Brainbow strains (Stock No. 007901, Stock No. 007911, Stock No. 007921) for neurobiological studies. This mouse can be used to support research in many areas including:
Neurobiology Research
* Cre-lox System (loxP-flanked Sequences)
* Fluorescent protein expression in neural tissue
Research Tools
* Cre-lox-System (loxP-flanked Sequences: Test/Reporter)
* Developmental Biology Research (Cre-lox system)
* Developmental Biology Research (transplantation marker for embryonic and adult tissue)
* FLP-FRT System (FRT-flanked Sequences)
* Fluorescent Proteins * Genetics Research (Mutagenesis and Transgenesis: Cre-lox system) * Genetics Research (Tissue/Cell Markers: Cre-lox system) * Genetics Research (Tissue/Cell Markers: astrocyte-specific marker) * Genetics Research (Tissue/Cell Markers: astrocytes) * Genetics Research (Tissue/Cell Markers: astrocytes, neurons) * Genetics Research (Tissue/Cell Markers: glial cells) * Genetics Research (Tissue/Cell Markers: multiple) * Genetics Research (Tissue/Cell Markers: neurons) * Genetics Research (Tissue/Cell Markers: transplantation marker for embryonic and adult tissue) * Neurobiology Research (astrocyte-specific marker) * Neurobiology Research (cell marker) * YFP related Research Tools * Fluorescent Proteins Control: 000664 C57BL/6J (approximate)
Mus musculus with name STOCK Tg(Thy1-EGFP)MJrs/J from IMSR.
View all literature mentionsMus musculus with name STOCK Tg(Thy1-EGFP)MJrs/J from IMSR.
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