Abstract
In contextual fear conditioning (CFC) a single training leads to long-term memory of context-aversive electrical foot-shocks association. Mid-temporal regions of the brain of trained and naive rats were obtained 2 days after conditioning and screened by two-directional suppression subtractive hybridization. A pool of differentially expressed genes was identified and some of them were randomly selected and confirmed with qRT-PCR assay. These transcripts showed high homology for rat gene sequences coding for proteins involved in different cellular processes. The expression of the selected transcripts was also tested in rats which had freely explored the experimental apparatus (exploration) and in rats to which the same number of aversive shocks had been administered in the same apparatus, but temporally compressed so as to make the association between painful stimuli and the apparatus difficult (shock-only). Some genes resulted differentially expressed only in the rats subjected to CFC, others only in exploration or shock-only rats, whereas the gene coding for translocase of outer mitochondrial membrane 20 protein and nardilysin were differentially expressed in both CFC and exploration rats. For example, the expression of stathmin 1 whose transcripts resulted up regulated was also tested to evaluate the transduction and protein localization after conditioning.
Highlights
Memory is the capacity to retain learned information
Studies in both Aplysia and Drosophila systems allowed the discovery of the first molecular pathway essential for memory consolidation, that is the cyclic AMP-protein kinase A (PKA)-cAMP response element-binding protein (CREB)-CCAAT enhancer-binding protein (C/EBP)dependent pathway [4,5]
Increasing evidence has shown, in several learning tasks and different species, that induction of LT memory depends on the temporally limited phase of mRNA and protein synthesis so that transcription, like translation, is an essential step for memory formation [6,7,8,9] and memory consolidation requires de novo mRNA and protein synthesis for several hours [8,10,11,12,13,14,15]
Summary
Memory is the capacity to retain learned information. On the basis of its duration, we can distinguish short-term (ST) and longterm (LT) memories which are accompanied by different biological states and mechanisms of retention and they are two distinct forms of memory. Increasing evidence has shown, in several learning tasks and different species, that induction of LT memory depends on the temporally limited phase of mRNA and protein synthesis so that transcription, like translation, is an essential step for memory formation [6,7,8,9] and memory consolidation requires de novo mRNA and protein synthesis for several hours [8,10,11,12,13,14,15]. More recently the use of technologies to quantify alterations in gene expression in brain tissue has provided new and important insights about how gene expression is altered by experience and how these molecular changes may provide a substrate for the LT storage of new memories
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