SYNAPTIC ACTIVITY-DEPENDENT MODULATION OF MITOCHONDRIAL GENE-EXPRESSION IN THE RAT HIPPOCAMPUS

In order to identify genes that may underlie the maintenance of long-t erm potentiation (LTP) at perforant path synapses, complementary DNA l ibraries were synthesised from dentate gyrus total RNA extracts prepar ed 48 h after the induction of LTP and from control dentate gyrus extr acts. Through differential screening of the LTP library we have identi fied the mitochondrial 12S rRNA (mt12SrRNA) as a transcript that was e levated at this late time. Northern blot analyses showed that the elev ation in mt12SrRNA expression began around 8 h and persisted for at le ast 2 weeks post-tetanus. We then examined the expression patterns of other mitochondrially-encoded genes and demonstrated a similar elevati on in their expression, mt12SrRNA levels were also elevated in other h ippocampal regions, including areas CA3 and CA1 and were elevated foll owing low-frequency stimulation or in the presence of an N-methyl-D-as partate receptor antagonist where induction of LTP was precluded. Take n together, these observations suggest that a long-lasting up-regulati on 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. (C) 1998 Elsevier Sc ience B.V. All rights reserved.