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Fos imaging reveals ageing‐related changes in hippocampal response to radial maze discrimination testing in mice
Author(s) -
Touzani Khalid,
Marighetto Aline,
Jaffard Robert
Publication year - 2003
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2003.02464.x
Subject(s) - hippocampal formation , hippocampus , radial arm maze , neuroscience , psychology , c fos , working memory , chemistry , cognition , gene expression , biochemistry , gene
A two‐stage radial arm maze (RAM) task has been designed recently to demonstrate a specific age‐related memory deficit in mice. It highlights the contrast between normal and deficient memory expression in a spatial discrimination problem depending on how to‐be discriminated arms were presented to the animal. This specific deficit has been interpreted as a preferential loss in a relational/declarative form of memory, thereby implying an underlying hippocampal dysfunction. To test this hypothesis, neuronal activation measured by Fos immunostaining was compared in aged (21–23 months) and adult (4–6 months) mice trained in the aforementioned task and killed after a retention session consisting in age‐insensitive probe trials, performed 6 days later (6‐day RAM). Two comparison conditions were included: (i) repeated locomotor training on a treadmill (TM); (ii) the same RAM training, except for the use of a longer (30 days instead of six) retention interval (30‐day RAM). Although all RAM groups displayed similar levels of performance at the end of the experiment, immediately before the mice were killed, significant between‐group differences in brain activation were observed. In adult mice, 6‐day RAM testing was associated with greater septal and hippocampal (CA1, CA3, DG) Fos expression than the TM condition. Lengthening the retention interval from 6 days to 30 days resulted in a significant decrease in RAM testing‐induced Fos expression in most of the septo‐hippocampal regions. With respect to adult mice, aged mice displayed reduced Fos expression (except for DG) and a lack of interrelationships between levels of Fos produced in each of the SH regions, in the 6‐day RAM testing condition. Conversely, there was no effect of ageing on Fos expression associated with either TM training or 30‐day RAM testing. These results are interpreted as reflecting age‐ (or time‐) related alterations in recruiting of brain structures that underlie a relational/declarative form of memory expression.