Synaptic activity-dependent modulation of mitochondrial gene expression in the rat hippocampus.

In order to identify genes that may underlie the maintenance of long-term potentiation (LTP) at perforant path synapses, complementary DNA libraries were synthesised from dentate gyrus total RNA extracts prepared 48 h after the induction of LTP and from control dentate gyrus extracts. Through differential screening of the LTP library we have identified the mitochondrial 12S rRNA (mt12SrRNA) as a transcript that was elevated at this late time. Northern blot analyses showed that the elevation in mt12SrRNA expression began around 8 h and persisted for at least 2 weeks post-tetanus. We then examined the expression patterns of other mitochondrially-encoded genes and demonstrated a similar elevation in their expression. mt12SrRNA levels were also elevated in other hippocampal regions, including areas CA3 and CA1 and were elevated following low-frequency stimulation or in the presence of an N-methyl-D-aspartate receptor antagonist where induction of LTP was precluded. Taken together, these observations suggest that a long-lasting up-regulation of energy production may be triggered by synaptic activity and this activity need not be of sufficient strength to induce LTP, but may be related to the induction of a metaplastic state. Copyright 1998 Elsevier Science B.V.