No evidence for age-associated alterations in zif268 mRNA expression in CA1 pyramidal neurons.
1. ARL NSMA, University of Arizona, Tucson, AZ
2. Dept Neurosci, Johns Hopkins University, Baltimore, MD
Neuronal plasticity is mediated, at least in part, by the expression of immediate-early genes (IEGs). Of this class of genes, both Arc and zif268 are known to be critical for LTP persistence and long-term memory for hippocampal-dependent tasks, both of which are compromised in the aged animal. Some experimental evidence exists to support the hypothesis that such changes may be at least partly mediated by subtle alterations in IEG expression. For example, although it has been previously demonstrated that the proportion of CA1 and CA3 pyramidal neurons that transcribe Arc is not affected in the aged rat (Small et al., 2004), qRT-PCR data indicates that there is indeed a small but significant reduction in the amount of Arc mRNA in the aged CA1 relative to the adult CA1. Similar experiments have not been undertaken for zif268, which has recently been shown to regulate protein synthesis independent expression of Arc in adult animals following seizure and exploration of a novel environment (Li et al., 2005). In this study, we investigated potential age-related changes in zif268 transcription in area CA1 as well as the coordinate transcriptional response of Arc and zif268 following brief exploration of a novel environment. Our results indicate that a similar proportion of CA1 pyramidal neurons transcribe zif268 in aged and adult rats; for both age groups ~35-40% of the pyramidal neurons analyzed were zif268+. Further, we observed that the majority of zif268+ neurons were also Arc+ for both adult and aged rats. Finally, qRT-PCR indicated no significant age-related difference in the amount of zif268 found in this particular hippocampal subregion. It is unlikely, therefore, that age-associated alterations in CA1 function are the result of changes in zif268 expression.
Supported by: AG009219
Key Words: Immediate-early gene; Hippocampus; Aging