Age‐related alterations of extracellular signal‐regulated kinase 2 mRNA expression in the rat brain

Abstract

Aging is accompanied by the loss of memory and cognitive functions. Recent studies indicated that extracellular signal‐regulated kinases (ERKs) play an essential role in synaptic plasticity and memory. A selective activation of ERK2 has been demonstrated in the hippocampus during long‐term potentiation and in different in vivo learning paradigms. In this study, we investigated age differences in the expression of ERK2 by quantitative in situ hybridization using male Fisher 344 rats 3, 12 and 25 months of age. The results show an intense expression of ERK2 mRNA in many brain regions including the hippocampus, the cerebral cortex, the caudate‐putamen and the cerebellum. Moderate expression was found in the thalamus and the hypothalamus. No age‐dependent changes in ERK2 mRNA expression were detected in most cortical areas except for a slight decreasing trend in the pyriform cortex. ERK2 mRNA expression remained stable in the dentate gyrus and CA1 region of the hippocampus during aging. However, an early decline in ERK2 mRNA level was found in the CA3 region. Several behavioral studies have provided evidence that new protein synthesis in the CA3 region is necessary for memory consolidation during the first 1–2 days after learning. ERK2 is a regulator of neuronal gene expression and hippocampal ERK2 activation has been demonstrated in vivo in different learning paradigms. Thus, the early decrease in ERK2 mRNA in the CA3 region may underlie age‐related impairments in learning and memory.Acknowledgements: PO1 AG 18357 from NIH.