It is well known that there are behavioral and cognitive age-dependent peculiarities. The neuronal bases of such peculiarities are still to be determined. In order to reveal possible mechanisms of age-dependent learning abilities we assessed changes in neuronal gene expression (based on c-Fos induction) in the rat cerebral cortex after instrumental learning on different age because learning has been shown to induce changes in neuronal gene expression. Long-Evans rats of 2 different age groups (“young” – 1.5 to 6 months old and “old” – 17 to 21 months old) were trained the lever-press task over a period of several days. During the last session animals were retrained the same behavior on the second side of the experimental chamber. Seventy five minutes after the last experimental session the animals were overdosed with ether, and the brains were removed and frozen for analysis. The brains were processed for Nissle-staining in order to determine the number of neurons in the cerebral cortex and for immunohistochemistry in order to determine the number of Fos-positive neurons. Analysis of the behavior showed that rats of all groups were able to learn the task during the last 30-minute session. There were no significant differences found in the number of neurons between “young” and “old” rats in both anterolateral and retrosplenial cortices. Immunohystochemistry showed the decreased number of Fos-positive neurons in the “old” rat somatosensory cortex as compared to “young” ones. There were no significant differences in the number of Fos-positive neurons of “young” and “old” rats in anterolateral or retrosplenial cortices. Our results show that the number of neurons does not differ on different age stages. However, some of those neurons do not undergo plasticity changes anymore as revealed by decreased c-Fos induction in cells. It might be suggested that individual experience growth with age results in the increase in the number of neuronal systems and, at the same time, in reduced susceptibility of neurons to plasticity changes during learning.
ЦИТАТА
Tulinova, E.V. Effects of aging on learning-induced c-Fos expression and neuron density in the rat brain. / E.V. Tulinova, O.E. Svarnik, Y.I. Alexandrov // International Journal of Psychophysiology. – 2008. – Т. 69. – № 3. – P. 255-256
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